v0.11.0

- Add `add_mutable_global`
- Add `add_userdata_type`
- Replace `set_library_constants` with `add_library_constant`
- Add `add_disabled_builtin`

.github/workflows/coverage.yml

@@ -6,18 +6,18 @@ jobs:
     name: coverage
     runs-on: ubuntu-latest
     container:
-      image: xd009642/tarpaulin
+      image: xd009642/tarpaulin:develop-nightly
       options: --security-opt seccomp=unconfined
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@main
 
       - name: Generate coverage report
         run: |
-          cargo tarpaulin --out xml --tests --exclude-files benches/* --exclude-files mlua-sys/src/*/*
+          cargo +nightly tarpaulin --verbose --out xml --tests --exclude-files benches/* --exclude-files mlua-sys/src/*/*
 
       - name: Upload report to codecov.io
-        uses: codecov/codecov-action@v3
+        uses: codecov/codecov-action@v4
         with:
           token: ${{secrets.CODECOV_TOKEN}}
           fail_ci_if_error: false

.github/workflows/main.yml

@@ -7,18 +7,18 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-22.04, macos-latest, windows-latest]
+        os: [ubuntu-latest, macos-latest, windows-latest]
         rust: [stable]
         lua: [lua54, lua53, lua52, lua51, luajit, luau, luau-jit, luau-vector4]
         include:
-          - os: ubuntu-22.04
+          - os: ubuntu-latest
             target: x86_64-unknown-linux-gnu
           - os: macos-latest
             target: x86_64-apple-darwin
           - os: windows-latest
             target: x86_64-pc-windows-msvc
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@main
       - uses: dtolnay/rust-toolchain@stable
         with:
           toolchain: ${{ matrix.rust }}
@@ -27,11 +27,11 @@ jobs:
       - name: Build ${{ matrix.lua }} vendored
         run: |
           cargo build --features "${{ matrix.lua }},vendored"
-          cargo build --features "${{ matrix.lua }},vendored,async,serialize,macros"
-          cargo build --features "${{ matrix.lua }},vendored,async,serialize,macros,send"
+          cargo build --features "${{ matrix.lua }},vendored,async,serde,macros,anyhow,userdata-wrappers"
+          cargo build --features "${{ matrix.lua }},vendored,async,serde,macros,anyhow,userdata-wrappers,send"
         shell: bash
       - name: Build ${{ matrix.lua }} pkg-config
-        if: ${{ matrix.os == 'ubuntu-22.04' }}
+        if: ${{ matrix.os == 'ubuntu-latest' }}
         run: |
           sudo apt-get update
           sudo apt-get install -y --no-install-recommends liblua5.4-dev liblua5.3-dev liblua5.2-dev liblua5.1-0-dev libluajit-5.1-dev
@@ -45,23 +45,23 @@ jobs:
       matrix:
         lua: [lua54, lua53, lua52, lua51, luajit]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@main
       - uses: dtolnay/rust-toolchain@stable
         with:
           toolchain: stable
           target: aarch64-apple-darwin
       - name: Cross-compile
-        run: cargo build --target aarch64-apple-darwin --features "${{ matrix.lua }},vendored,async,send,serialize,macros"
+        run: cargo build --target aarch64-apple-darwin --features "${{ matrix.lua }},vendored,async,send,serde,macros,anyhow,userdata-wrappers"
 
   build_aarch64_cross_ubuntu:
     name: Cross-compile to aarch64-unknown-linux-gnu
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     needs: build
     strategy:
       matrix:
         lua: [lua54, lua53, lua52, lua51, luajit]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@main
       - uses: dtolnay/rust-toolchain@stable
         with:
           toolchain: stable
@@ -72,18 +72,18 @@ jobs:
           sudo apt-get install -y --no-install-recommends gcc-aarch64-linux-gnu libc6-dev-arm64-cross
         shell: bash
       - name: Cross-compile
-        run: cargo build --target aarch64-unknown-linux-gnu --features "${{ matrix.lua }},vendored,async,send,serialize,macros"
+        run: cargo build --target aarch64-unknown-linux-gnu --features "${{ matrix.lua }},vendored,async,send,serde,macros,anyhow,userdata-wrappers"
         shell: bash
 
   build_armv7_cross_ubuntu:
     name: Cross-compile to armv7-unknown-linux-gnueabihf
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     needs: build
     strategy:
       matrix:
         lua: [lua54, lua53, lua52, lua51]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@main
       - uses: dtolnay/rust-toolchain@stable
         with:
           toolchain: stable
@@ -94,7 +94,7 @@ jobs:
           sudo apt-get install -y --no-install-recommends gcc-arm-linux-gnueabihf libc-dev-armhf-cross
         shell: bash
       - name: Cross-compile
-        run: cargo build --target armv7-unknown-linux-gnueabihf --features "${{ matrix.lua }},vendored,async,send,serialize,macros"
+        run: cargo build --target armv7-unknown-linux-gnueabihf --features "${{ matrix.lua }},vendored,async,send,serde,macros,anyhow,userdata-wrappers"
         shell: bash
 
   test:
@@ -103,18 +103,18 @@ jobs:
     needs: build
     strategy:
       matrix:
-        os: [ubuntu-22.04, macos-latest, windows-latest]
+        os: [ubuntu-latest, macos-latest, windows-latest]
         rust: [stable, nightly]
         lua: [lua54, lua53, lua52, lua51, luajit, luajit52, luau, luau-jit, luau-vector4]
         include:
-          - os: ubuntu-22.04
+          - os: ubuntu-latest
             target: x86_64-unknown-linux-gnu
           - os: macos-latest
             target: x86_64-apple-darwin
           - os: windows-latest
             target: x86_64-pc-windows-msvc
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@main
       - uses: dtolnay/rust-toolchain@stable
         with:
           toolchain: ${{ matrix.rust }}
@@ -123,14 +123,14 @@ jobs:
       - name: Run ${{ matrix.lua }} tests
         run: |
           cargo test --features "${{ matrix.lua }},vendored"
-          cargo test --features "${{ matrix.lua }},vendored,async,serialize,macros"
-          cargo test --features "${{ matrix.lua }},vendored,async,serialize,macros,send"
+          cargo test --features "${{ matrix.lua }},vendored,async,serde,macros,anyhow,userdata-wrappers"
+          cargo test --features "${{ matrix.lua }},vendored,async,serde,macros,anyhow,userdata-wrappers,send"
         shell: bash
       - name: Run compile tests (macos lua54)
         if: ${{ matrix.os == 'macos-latest' && matrix.lua == 'lua54' }}
         run: |
-          TRYBUILD=overwrite cargo test --features "${{ matrix.lua }},vendored" -- --ignored
-          TRYBUILD=overwrite cargo test --features "${{ matrix.lua }},vendored,async,send,serialize,macros" -- --ignored
+          TRYBUILD=overwrite cargo test --features "${{ matrix.lua }},vendored" --tests -- --ignored
+          TRYBUILD=overwrite cargo test --features "${{ matrix.lua }},vendored,async,send,serde,macros" --tests -- --ignored
         shell: bash
 
   test_with_sanitizer:
@@ -139,14 +139,14 @@ jobs:
     needs: build
     strategy:
       matrix:
-        os: [ubuntu-22.04]
+        os: [ubuntu-latest]
         rust: [nightly]
         lua: [lua54, lua53, lua52, lua51, luajit, luau, luau-jit, luau-vector4]
         include:
-          - os: ubuntu-22.04
+          - os: ubuntu-latest
             target: x86_64-unknown-linux-gnu
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@main
       - uses: dtolnay/rust-toolchain@stable
         with:
           toolchain: ${{ matrix.rust }}
@@ -154,28 +154,54 @@ jobs:
       - uses: Swatinem/rust-cache@v2
       - name: Run ${{ matrix.lua }} tests with address sanitizer
         run: |
-          cargo test --tests --features "${{ matrix.lua }},vendored,async,serialize,macros" --target x86_64-unknown-linux-gnu -- --skip test_too_many_recursions
-          cargo test --tests --features "${{ matrix.lua }},vendored,async,serialize,macros,send" --target x86_64-unknown-linux-gnu -- --skip test_too_many_recursions
+          cargo test --tests --features "${{ matrix.lua }},vendored,async,serde,macros,anyhow" --target x86_64-unknown-linux-gnu -- --skip test_too_many_recursions
+          cargo test --tests --features "${{ matrix.lua }},vendored,async,serde,macros,anyhow,userdata-wrappers,send" --target x86_64-unknown-linux-gnu -- --skip test_too_many_recursions
         shell: bash
         env:
           RUSTFLAGS: -Z sanitizer=address
 
+  test_with_memory_limit:
+    name: Test with memory limit
+    runs-on: ${{ matrix.os }}
+    needs: build
+    strategy:
+      matrix:
+        os: [ubuntu-latest]
+        rust: [nightly]
+        lua: [lua54, lua53, lua52, lua51, luajit, luau, luau-jit, luau-vector4]
+        include:
+          - os: ubuntu-latest
+            target: x86_64-unknown-linux-gnu
+    steps:
+      - uses: actions/checkout@main
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          toolchain: ${{ matrix.rust }}
+          target: ${{ matrix.target }}
+      - uses: Swatinem/rust-cache@v2
+      - name: Run ${{ matrix.lua }} tests with forced memory limit
+        run: |
+          cargo test --tests --features "${{ matrix.lua }},vendored,async,send,serde,macros,anyhow,userdata-wrappers"
+        shell: bash
+        env:
+          RUSTFLAGS: --cfg=force_memory_limit
+
   test_modules:
     name: Test modules
     runs-on: ${{ matrix.os }}
     needs: build
     strategy:
       matrix:
-        os: [ubuntu-22.04, macos-latest]
+        os: [ubuntu-latest, macos-latest]
         rust: [stable]
-        lua: [lua54, lua53, lua52, lua51, luajit, luau]
+        lua: [lua54, lua53, lua52, lua51, luajit]
         include:
-          - os: ubuntu-22.04
+          - os: ubuntu-latest
             target: x86_64-unknown-linux-gnu
           - os: macos-latest
             target: x86_64-apple-darwin
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@main
       - uses: dtolnay/rust-toolchain@stable
         with:
           toolchain: ${{ matrix.rust }}
@@ -199,7 +225,7 @@ jobs:
         shell: msys2 {0}
     steps:
       - uses: msys2/setup-msys2@v2
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@main
       - name: Install Rust & Lua
         run: |
           pacman -S --noconfirm mingw-w64-x86_64-rust mingw-w64-x86_64-lua mingw-w64-x86_64-luajit mingw-w64-x86_64-pkg-config
@@ -210,13 +236,13 @@ jobs:
 
   test_wasm32_emscripten:
     name: Test on wasm32-unknown-emscripten
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     needs: build
     strategy:
       matrix:
         lua: [lua54, lua53, lua52, lua51, luau]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@main
       - uses: dtolnay/rust-toolchain@stable
         with:
           toolchain: stable
@@ -228,13 +254,13 @@ jobs:
       - name: Run ${{ matrix.lua }} tests
         run: |
           cargo test --tests --features "${{ matrix.lua }},vendored"
-          cargo test --tests --features "${{ matrix.lua }},vendored,async,serialize,macros"
+          cargo test --tests --features "${{ matrix.lua }},vendored,async,serde,macros,anyhow,userdata-wrappers"
 
   rustfmt:
     name: Rustfmt
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@main
       - uses: dtolnay/rust-toolchain@nightly
         with:
           components: rustfmt
@@ -242,12 +268,12 @@ jobs:
 
   clippy:
     name: Clippy
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     strategy:
       matrix:
         lua: [lua54, lua53, lua52, lua51, luajit, luau, luau-jit, luau-vector4]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@main
       - uses: dtolnay/rust-toolchain@stable
         with:
           toolchain: nightly
@@ -255,4 +281,4 @@ jobs:
       - uses: giraffate/clippy-action@v1
         with:
           reporter: 'github-pr-review'
-          clippy_flags: --features "${{ matrix.lua }},vendored,async,send,serialize,macros"
+          clippy_flags: --features "${{ matrix.lua }},vendored,async,send,serde,macros,anyhow,userdata-wrappers"

.github/workflows/typos.yml

@@ -0,0 +1,17 @@
+name: Typos Check
+on:
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  run:
+    name: Spell Check with Typos
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout Actions Repository
+      uses: actions/checkout@v4
+
+    - name: Check spelling
+      uses: crate-ci/typos@master
+      with:
+        config: ./typos.toml

CHANGELOG.md

@@ -1,3 +1,121 @@
+## v0.11.0 (Jul 14, 2025)
+
+Changes since v0.11.0-beta.3
+
+- Allow linking external Lua libraries in a build script (e.g. pluto) using `external` mlua-sys feature flag
+- `Lua::inspect_stack` takes a callback with `&Debug` argument, instead of returning `Debug` directly
+- Added `Debug::function` method to get function running at a given level
+- `Debug::curr_line` is deprecated in favour of `Debug::current_line` that returns `Option<usize>`
+- Added `Lua::set_globals` method to replace global environment
+- `Table::set_metatable` now returns `Result<()>` (this operation can fail in sandboxed Luau mode)
+- `impl ToString` replaced with `Into<StdString>`  in `UserData` registration
+- `Value::as_str` and `Value::as_string_lossy` methods are deprecated (as they are non-idiomatic)
+- Bugfixes and improvements
+
+## v0.11.0-beta.3 (Jun 23, 2025)
+
+- Luau in sandboxed mode has reduced options in `collectgarbage` function (to follow the official doc)
+- `Function::deep_clone` now returns `Result<Function>` as this operation can trigger memory errors
+- Luau "Require" resolves included Lua files relative to the current directory (#605)
+- Fixed bug when finalizing `AsyncThread` on drop (`call_async` methods family)
+
+## v0.11.0-beta.2 (Jun 12, 2025)
+
+- Lua 5.4 updated to 5.4.8
+- Terminate Rust `Future` when `AsyncThread` is dropped (without relying on Lua GC)
+- Added `loadstring` function to Luau
+- Make `AsChunk` trait dyn-friendly
+- Luau `Require` trait synced with Luau 0.674
+- Luau `Require` trait methods now can return `Error` variant (in `NavigateError` enum)
+- Added `__type` to `Error`'s userdata metatable (for `typeof` function)
+- `parking_log/send_guard` is moved to `userdata-wrappers` feature flag
+- New `serde` feature flag to replace `serialize` (the old one is still available)
+
+## v0.11.0-beta.1 (May 7th, 2025)
+
+- New "require-by-string" for Luau (with `Require` trait and async support)
+- Added `Thread::resume_error` support for Luau
+- 52 bit integers support for Luau (this is a breaking change)
+- New features for Luau compiler (constants, disabled builtins, known members)
+- `AsyncThread<A, R>` changed to `AsyncThread<R>` (`A` pushed to stack immediately)
+- Lifetime `'a` moved from `AsChunk<'a>` to `AsChunk::source where Self: 'a`
+- `Lua::scope` pass `&Scope` instead of `&mut Scope` to closure
+- Added global hooks support (Lua 5.1+)
+- Added per-thread hooks support (Lua 5.1+)
+- `Lua::init_from_ptr` renamed to `Lua::get_or_init_from_ptr` and returns `&Lua`
+- `Lua:load_from_function` is deprecated (this is `register_module` now)
+- Added `Lua::register_module` and `Lua::preload_module`
+
+## v0.10.4 (May 5th, 2025)
+
+- Luau updated to 0.672
+- New serde option `encode_empty_tables_as_array` to serialize empty tables as arrays
+- Added `WeakLua` and `Lua::weak()` to create weak references to Lua state
+- Trigger abort when Luau userdata destructors are panic (Luau GC does not support it)
+- Added `AnyUserData::type_id()` method to get the type id of the userdata
+- Added `Chunk::name()`, `Chunk::environment()` and `Chunk::mode()` functions
+- Support borrowing underlying wrapped types for `UserDataRef` and `UserDataRefMut` (under `userdata-wrappers` feature)
+- Added large (52bit) integers support for Luau
+- Enable `serde` for `bstr` if `serialize` feature flag is enabled
+- Recursive warnings (Lua 5.4) are no longer allowed
+- Implemented `IntoLua`/`FromLua` for `BorrowedString` and `BorrowedBytes`
+- Implemented `IntoLua`/`FromLua` for `char`
+- Enable `Thread::reset()` for all Lua versions (limited support for 5.1-5.3)
+- Bugfixes and improvements
+
+## v0.10.3 (Jan 27th, 2025)
+
+- Set `Default` for `Value` to be `Nil`
+- Allow exhaustive match on `Value` (#502)
+- Add `Table::set_safeenv` method (Luau)
+
+## v0.10.2 (Dec 1st, 2024)
+
+- Switch proc-macro-error to proc-macro-error2 (#493)
+- Do not allow Lua to run GC finalizers on ref thread (#491)
+- Fix chunks loading in Luau when memory limit is enforced (#488)
+- Added `String::wrap` method to wrap arbitrary `AsRef<[u8]>` into `impl IntoLua`
+- Better FreeBSD/OpenBSD support (thanks to cos)
+- Delay "any" userdata metatable creation until first instance is created (#482)
+- Reduce amount of generated code for `UserData` (less generics)
+
+## v0.10.1 (Nov 9th, 2024)
+
+- Minimal Luau updated to 0.650
+- Added Luau native vector library support (this can change behavior if you use `vector` function!)
+- Added Lua `String::display` method
+- Improved pretty-printing for Lua tables (#478)
+- Added `Scope::create_any_userdata` to create Lua objects from any non-`'static` Rust types
+- Added `AnyUserData::destroy` method
+- New `userdata-wrappers` feature to `impl UserData` for `Rc<T>`/`Arc<T>`/`Rc<RefCell<T>>`/`Arc<Mutex<T>>` (similar to v0.9)
+- `UserDataRef` in `send` mode now uses shared lock if `T: Sync` (and exclusive lock otherwise)
+- Added `Scope::add_destructor` to attach custom destructors
+- Added `Lua::try_app_data_ref` and `Lua::try_app_data_mut` methods
+- Added `From<Vec>` and `Into<Vec>` support to `MultiValue` and `Variadic` types
+- Bug fixes and improvements (#477 #479)
+
+## v0.10.0 (Oct 25th, 2024)
+
+Changes since v0.10.0-rc.1
+
+- Added `error-send` feature flag (disabled by default) to require `Send + Sync` for `Error`
+- Some performance improvements
+
+## v0.10.0-rc.1
+
+- `Lua::scope` is back
+- Support yielding from hooks for Lua 5.3+
+- Support setting metatable for Lua builtin types (number/string/function/etc)
+- Added `LuaNativeFn`/`LuaNativeFnMut`/`LuaNativeAsyncFn` traits for using in `Function::wrap`
+- Added `Error::chain` method to return iterator over nested errors
+- Added `Lua::exec_raw` helper to execute low-level Lua C API code
+- Added `Either<L, R>` enum to combine two types into a single one
+- Added a new `Buffer` type for Luau
+- Added `Value::is_error` and `Value::as_error` helpers
+- Added `Value::Other` variant to represent unknown Lua types (eg LuaJIT CDATA)
+- Added (optional) `anyhow` feature to implement `IntoLua` for `anyhow::Error`
+- Added `IntoLua`/`FromLua` for `OsString`/`OsStr` and `PathBuf`/`Path`
+
 ## v0.10.0-beta.2
 
 - Updated `ThreadStatus` enum to include `Running` and `Finished` variants.
@@ -251,7 +369,7 @@ Other:
 
 ## v0.8.0
 Changes since 0.7.4
-- Roblox Luau support
+- Luau support
 - Removed C glue
 - Added async support to `__index` and `__newindex` metamethods
 - Added `Function::info()` to get information about functions (#149).
@@ -301,7 +419,7 @@ Breaking changes:
 
 ## v0.8.0-beta.1
 
-- Roblox Luau support
+- Luau support
 - Refactored ffi module. C glue is no longer required
 - Added async support to `__index` and `__newindex` metamethods
 
@@ -414,7 +532,7 @@ Breaking changes:
 - [**Breaking**] Removed `AnyUserData::has_metamethod()`
 - Added `Thread::reset()` for luajit/lua54 to recycle threads.
   It's possible to attach a new function to a thread (coroutine).
-- Added `chunk!` macro support to load chunks of Lua code using the Rust tokenizer and optinally capturing Rust variables.
+- Added `chunk!` macro support to load chunks of Lua code using the Rust tokenizer and optionally capturing Rust variables.
 - Improved error reporting (`Error`'s `__tostring` method formats full stacktraces). This is useful in the module mode.
 
 ## v0.6.0-beta.1
@@ -470,7 +588,7 @@ Breaking changes:
 
 - Lua 5.4 support with `MetaMethod::Close`.
 - `lua53` feature is disabled by default. Now preferred Lua version have to be chosen explicitly.
-- Provide safety guaraness for Lua state, which means that potenially unsafe operations, like loading C modules (using `require` or `package.loadlib`) are disabled. Equalient for the previous `Lua::new()` function is `Lua::unsafe_new()`.
+- Provide safety guarantees for Lua state, which means that potentially unsafe operations, like loading C modules (using `require` or `package.loadlib`) are disabled. Equivalent to the previous `Lua::new()` function is `Lua::unsafe_new()`.
 - New `send` feature to require `Send`.
 - New `module` feature, that disables linking to Lua Core Libraries. Required for modules.
 - Don't allow `'callback` outlive `'lua` in `Lua::create_function()` to fix [the unsoundness](tests/compile/static_callback_args.rs).

Cargo.toml

@@ -1,22 +1,22 @@
 [package]
 name = "mlua"
-version = "0.10.0-beta.2" # remember to update mlua_derive
+version = "0.11.0" # remember to update mlua_derive
 authors = ["Aleksandr Orlenko <zxteam@pm.me>", "kyren <catherine@kyju.org>"]
 rust-version = "1.79.0"
 edition = "2021"
-repository = "https://github.com/khvzak/mlua"
+repository = "https://github.com/mlua-rs/mlua"
 documentation = "https://docs.rs/mlua"
 readme = "README.md"
 keywords = ["lua", "luajit", "luau", "async", "scripting"]
 categories = ["api-bindings", "asynchronous"]
 license = "MIT"
 description = """
-High level bindings to Lua 5.4/5.3/5.2/5.1 (including LuaJIT) and Roblox Luau
+High level bindings to Lua 5.4/5.3/5.2/5.1 (including LuaJIT) and Luau
 with async/await features and support of writing native Lua modules in Rust.
 """
 
 [package.metadata.docs.rs]
-features = ["lua54", "vendored", "async", "send", "serialize", "macros"]
+features = ["lua54", "vendored", "async", "send", "serde", "macros"]
 rustdoc-args = ["--cfg", "docsrs"]
 
 [workspace]
@@ -32,19 +32,26 @@ lua52 = ["ffi/lua52"]
 lua51 = ["ffi/lua51"]
 luajit = ["ffi/luajit"]
 luajit52 = ["luajit", "ffi/luajit52"]
-luau = ["ffi/luau", "dep:libloading"]
+luau = ["ffi/luau"]
 luau-jit = ["luau", "ffi/luau-codegen"]
 luau-vector4 = ["luau", "ffi/luau-vector4"]
 vendored = ["ffi/vendored"]
-module = ["dep:mlua_derive", "ffi/module"]
+module = ["mlua_derive", "ffi/module"]
 async = ["dep:futures-util"]
-send = ["parking_lot/send_guard"]
-serialize = ["dep:serde", "dep:erased-serde", "dep:serde-value"]
+send = ["error-send"]
+error-send = []
+serde = ["dep:serde", "dep:erased-serde", "dep:serde-value", "bstr/serde"]
 macros = ["mlua_derive/macros"]
+anyhow = ["dep:anyhow", "error-send"]
+userdata-wrappers = ["parking_lot/send_guard"]
+
+# deprecated features
+serialize = ["serde"]
 
 [dependencies]
-mlua_derive = { version = "=0.10.0-beta.1", optional = true, path = "mlua_derive" }
+mlua_derive = { version = "=0.11.0", optional = true, path = "mlua_derive" }
 bstr = { version = "1.0", features = ["std"], default-features = false }
+either = "1.0"
 num-traits = { version = "0.2.14" }
 rustc-hash = "2.0"
 futures-util = { version = "0.3", optional = true, default-features = false, features = ["std"] }
@@ -52,11 +59,10 @@ serde = { version = "1.0", optional = true }
 erased-serde = { version = "0.4", optional = true }
 serde-value = { version = "0.7", optional = true }
 parking_lot = { version = "0.12", features = ["arc_lock"] }
+anyhow = { version = "1.0", optional = true }
+rustversion = "1.0"
 
-ffi = { package = "mlua-sys", version = "0.6.3", path = "mlua-sys" }
-
-[target.'cfg(unix)'.dependencies]
-libloading = { version = "0.8", optional = true }
+ffi = { package = "mlua-sys", version = "0.8.0", path = "mlua-sys" }
 
 [dev-dependencies]
 trybuild = "1.0"
@@ -72,8 +78,8 @@ tempfile = "3"
 static_assertions = "1.0"
 
 [target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]
-criterion = { version = "0.5", features = ["async_tokio"] }
-rustyline = "14.0"
+criterion = { version = "0.6", features = ["async_tokio"] }
+rustyline = "16.0"
 tokio = { version = "1.0", features = ["full"] }
 
 [lints.rust]
@@ -87,7 +93,7 @@ required-features = ["async"]
 [[bench]]
 name = "serde"
 harness = false
-required-features = ["serialize"]
+required-features = ["serde"]
 
 [[example]]
 name = "async_http_client"
@@ -95,7 +101,7 @@ required-features = ["async", "macros"]
 
 [[example]]
 name = "async_http_reqwest"
-required-features = ["async", "serialize", "macros"]
+required-features = ["async", "serde", "macros"]
 
 [[example]]
 name = "async_http_server"
@@ -110,8 +116,8 @@ name = "guided_tour"
 required-features = ["macros"]
 
 [[example]]
-name = "serialize"
-required-features = ["serialize"]
+name = "serde"
+required-features = ["serde"]
 
 [[example]]
 name = "userdata"

README.md

@@ -1,15 +1,15 @@
 # mlua
 [![Build Status]][github-actions] [![Latest Version]][crates.io] [![API Documentation]][docs.rs] [![Coverage Status]][codecov.io] ![MSRV]
 
-[Build Status]: https://github.com/khvzak/mlua/workflows/CI/badge.svg
-[github-actions]: https://github.com/khvzak/mlua/actions
+[Build Status]: https://github.com/mlua-rs/mlua/workflows/CI/badge.svg
+[github-actions]: https://github.com/mlua-rs/mlua/actions
 [Latest Version]: https://img.shields.io/crates/v/mlua.svg
 [crates.io]: https://crates.io/crates/mlua
 [API Documentation]: https://docs.rs/mlua/badge.svg
 [docs.rs]: https://docs.rs/mlua
 [Coverage Status]: https://codecov.io/gh/mlua-rs/mlua/branch/main/graph/badge.svg?token=99339FS1CG
 [codecov.io]: https://codecov.io/gh/mlua-rs/mlua
-[MSRV]: https://img.shields.io/badge/rust-1.71+-brightgreen.svg?&logo=rust
+[MSRV]: https://img.shields.io/badge/rust-1.79+-brightgreen.svg?&logo=rust
 
 [Guided Tour] | [Benchmarks] | [FAQ]
 
@@ -17,25 +17,23 @@
 [Benchmarks]: https://github.com/khvzak/script-bench-rs
 [FAQ]: FAQ.md
 
-# The main branch is the v0.10, development version of `mlua`. Please see the [v0.9](https://github.com/mlua-rs/mlua/tree/v0.9) branch for the stable versions of `mlua`.
+`mlua` is a set of bindings to the [Lua](https://www.lua.org) programming language for Rust with a goal to provide a
+_safe_ (as much as possible), high level, easy to use, practical and flexible API.
 
-`mlua` is bindings to [Lua](https://www.lua.org) programming language for Rust with a goal to provide
-_safe_ (as far as it's possible), high level, easy to use, practical and flexible API.
+Started as an `rlua` fork, `mlua` supports Lua 5.4, 5.3, 5.2, 5.1 (including LuaJIT) and [Luau] and allows writing native Lua modules in Rust as well as using Lua in a standalone mode.
 
-Started as `rlua` fork, `mlua` supports Lua 5.4, 5.3, 5.2, 5.1 (including LuaJIT) and [Roblox Luau] and allows to write native Lua modules in Rust as well as use Lua in a standalone mode.
+`mlua` is tested on Windows/macOS/Linux including module mode in [GitHub Actions] on `x86_64` platforms and cross-compilation to `aarch64` (other targets are also supported).
 
-`mlua` tested on Windows/macOS/Linux including module mode in [GitHub Actions] on `x86_64` platform and cross-compilation to `aarch64` (other targets are also supported).
+WebAssembly (WASM) is supported through `wasm32-unknown-emscripten` target for all Lua/Luau versions excluding JIT.
 
-WebAssembly (WASM) is supported through `wasm32-unknown-emscripten` target for all Lua versions excluding JIT.
-
-[GitHub Actions]: https://github.com/khvzak/mlua/actions
-[Roblox Luau]: https://luau-lang.org
+[GitHub Actions]: https://github.com/mlua-rs/mlua/actions
+[Luau]: https://luau.org
 
 ## Usage
 
 ### Feature flags
 
-`mlua` uses feature flags to reduce the amount of dependencies, compiled code and allow to choose only required set of features.
+`mlua` uses feature flags to reduce the amount of dependencies and compiled code, and allow to choose only required set of features.
 Below is a list of the available feature flags. By default `mlua` does not enable any features.
 
 * `lua54`: enable Lua [5.4] support
@@ -47,21 +45,24 @@ Below is a list of the available feature flags. By default `mlua` does not enabl
 * `luau`: enable [Luau] support (auto vendored mode)
 * `luau-jit`: enable [Luau] support with JIT backend.
 * `luau-vector4`: enable [Luau] support with 4-dimensional vector.
-* `vendored`: build static Lua(JIT) library from sources during `mlua` compilation using [lua-src] or [luajit-src] crates
+* `vendored`: build static Lua(JIT) libraries from sources during `mlua` compilation using [lua-src] or [luajit-src]
 * `module`: enable module mode (building loadable `cdylib` library for Lua)
 * `async`: enable async/await support (any executor can be used, eg. [tokio] or [async-std])
 * `send`: make `mlua::Lua: Send + Sync` (adds [`Send`] requirement to `mlua::Function` and `mlua::UserData`)
-* `serialize`: add serialization and deserialization support to `mlua` types using [serde] framework
+* `error-send`: make `mlua:Error: Send + Sync`
+* `serde`: add serialization and deserialization support to `mlua` types using [serde]
 * `macros`: enable procedural macros (such as `chunk!`)
+* `anyhow`: enable `anyhow::Error` conversion into Lua
+* `userdata-wrappers`: opt into `impl UserData` for `Rc<T>`/`Arc<T>`/`Rc<RefCell<T>>`/`Arc<Mutex<T>>` where `T: UserData`
 
 [5.4]: https://www.lua.org/manual/5.4/manual.html
 [5.3]: https://www.lua.org/manual/5.3/manual.html
 [5.2]: https://www.lua.org/manual/5.2/manual.html
 [5.1]: https://www.lua.org/manual/5.1/manual.html
 [LuaJIT]: https://luajit.org/
-[Luau]: https://github.com/Roblox/luau
-[lua-src]: https://github.com/khvzak/lua-src-rs
-[luajit-src]: https://github.com/khvzak/luajit-src-rs
+[Luau]: https://github.com/luau-lang/luau
+[lua-src]: https://github.com/mlua-rs/lua-src-rs
+[luajit-src]: https://github.com/mlua-rs/luajit-src-rs
 [tokio]: https://github.com/tokio-rs/tokio
 [async-std]: https://github.com/async-rs/async-std
 [`Send`]: https://doc.rust-lang.org/std/marker/trait.Send.html
@@ -71,7 +72,7 @@ Below is a list of the available feature flags. By default `mlua` does not enabl
 
 `mlua` supports async/await for all Lua versions including Luau.
 
-This works using Lua [coroutines](https://www.lua.org/manual/5.3/manual.html#2.6) and require running [Thread](https://docs.rs/mlua/latest/mlua/struct.Thread.html) along with enabling `feature = "async"` in `Cargo.toml`.
+This works using Lua [coroutines](https://www.lua.org/manual/5.3/manual.html#2.6) and requires running [Thread](https://docs.rs/mlua/latest/mlua/struct.Thread.html) along with enabling `feature = "async"` in `Cargo.toml`.
 
 **Examples**:
 - [HTTP Client](examples/async_http_client.rs)
@@ -86,18 +87,18 @@ This works using Lua [coroutines](https://www.lua.org/manual/5.3/manual.html#2.6
 cargo run --example async_http_client --features=lua54,async,macros
 
 # async http client (reqwest)
-cargo run --example async_http_reqwest --features=lua54,async,macros,serialize
+cargo run --example async_http_reqwest --features=lua54,async,macros,serde
 
 # async http server
 cargo run --example async_http_server --features=lua54,async,macros,send
 curl -v http://localhost:3000
 ```
 
-### Serialization (serde) support
+### Serde support
 
-With `serialize` feature flag enabled, `mlua` allows you to serialize/deserialize any type that implements [`serde::Serialize`] and [`serde::Deserialize`] into/from [`mlua::Value`]. In addition `mlua` provides [`serde::Serialize`] trait implementation for it (including `UserData` support).
+With the `serde` feature flag enabled, `mlua` allows you to serialize/deserialize any type that implements [`serde::Serialize`] and [`serde::Deserialize`] into/from [`mlua::Value`]. In addition, `mlua` provides the [`serde::Serialize`] trait implementation for `mlua::Value` (including `UserData` support).
 
-[Example](examples/serialize.rs)
+[Example](examples/serde.rs)
 
 [`serde::Serialize`]: https://docs.serde.rs/serde/ser/trait.Serialize.html
 [`serde::Deserialize`]: https://docs.serde.rs/serde/de/trait.Deserialize.html
@@ -107,28 +108,28 @@ With `serialize` feature flag enabled, `mlua` allows you to serialize/deserializ
 
 You have to enable one of the features: `lua54`, `lua53`, `lua52`, `lua51`, `luajit(52)` or `luau`, according to the chosen Lua version.
 
-By default `mlua` uses `pkg-config` tool to find lua includes and libraries for the chosen Lua version.
-In most cases it works as desired, although sometimes could be more preferable to use a custom lua library.
-To achieve this, mlua supports `LUA_LIB`, `LUA_LIB_NAME` and `LUA_LINK` environment variables.
+By default `mlua` uses `pkg-config` to find Lua includes and libraries for the chosen Lua version.
+In most cases it works as desired, although sometimes it may be preferable to use a custom Lua library.
+To achieve this, mlua supports the `LUA_LIB`, `LUA_LIB_NAME` and `LUA_LINK` environment variables.
 `LUA_LINK` is optional and may be `dylib` (a dynamic library) or `static` (a static library, `.a` archive).
 
-An example how to use them:
+An example of how to use them:
 ``` sh
 my_project $ LUA_LIB=$HOME/tmp/lua-5.2.4/src LUA_LIB_NAME=lua LUA_LINK=static cargo build
 ```
 
-`mlua` also supports vendored lua/luajit using the auxiliary crates [lua-src](https://crates.io/crates/lua-src) and
+`mlua` also supports vendored Lua/LuaJIT using the auxiliary crates [lua-src](https://crates.io/crates/lua-src) and
 [luajit-src](https://crates.io/crates/luajit-src).
-Just enable the `vendored` feature and cargo will automatically build and link specified lua/luajit version. This is the easiest way to get started with `mlua`.
+Just enable the `vendored` feature and cargo will automatically build and link the specified Lua/LuaJIT version. This is the easiest way to get started with `mlua`.
 
 ### Standalone mode
-In a standalone mode `mlua` allows to add to your application scripting support with a gently configured Lua runtime to ensure  safety and soundness.
+In standalone mode, `mlua` allows adding scripting support to your application with a gently configured Lua runtime to ensure safety and soundness.
 
-Add to `Cargo.toml` :
+Add to `Cargo.toml`:
 
 ``` toml
 [dependencies]
-mlua = { version = "0.9.9", features = ["lua54", "vendored"] }
+mlua = { version = "0.11", features = ["lua54", "vendored"] }
 ```
 
 `main.rs`
@@ -152,21 +153,21 @@ fn main() -> LuaResult<()> {
 ```
 
 ### Module mode
-In a module mode `mlua` allows to create a compiled Lua module that can be loaded from Lua code using [`require`](https://www.lua.org/manual/5.4/manual.html#pdf-require). In this case `mlua` uses an external Lua runtime which could lead to potential unsafety due to unpredictability of the Lua environment and usage of libraries such as [`debug`](https://www.lua.org/manual/5.4/manual.html#6.10).
+In module mode, `mlua` allows creating a compiled Lua module that can be loaded from Lua code using [`require`](https://www.lua.org/manual/5.4/manual.html#pdf-require). In this case `mlua` uses an external Lua runtime which could lead to potential unsafety due to the unpredictability of the Lua environment and usage of libraries such as [`debug`](https://www.lua.org/manual/5.4/manual.html#6.10).
 
 [Example](examples/module)
 
-Add to `Cargo.toml` :
+Add to `Cargo.toml`:
 
 ``` toml
 [lib]
 crate-type = ["cdylib"]
 
 [dependencies]
-mlua = { version = "0.9.9", features = ["lua54", "module"] }
+mlua = { version = "0.11", features = ["lua54", "module"] }
 ```
 
-`lib.rs` :
+`lib.rs`:
 
 ``` rust
 use mlua::prelude::*;
@@ -209,14 +210,14 @@ rustflags = [
 ```
 On Linux you can build modules normally with `cargo build --release`.
 
-On Windows the target module will be linked with `lua5x.dll` library (depending on your feature flags).
+On Windows the target module will be linked with the `lua5x.dll` library (depending on your feature flags).
 Your main application should provide this library.
 
-Module builds don't require Lua lib or headers to be installed on the system.
+Module builds don't require Lua binaries or headers to be installed on the system.
 
 ### Publishing to luarocks.org
 
-There is a LuaRocks build backend for mlua modules [`luarocks-build-rust-mlua`].
+There is a LuaRocks build backend for mlua modules: [`luarocks-build-rust-mlua`].
 
 Modules written in Rust and published to luarocks:
 - [`decasify`](https://github.com/alerque/decasify)
@@ -229,10 +230,10 @@ Modules written in Rust and published to luarocks:
 
 ## Safety
 
-One of the `mlua` goals is to provide *safe* API between Rust and Lua.
-Every place where the Lua C API may trigger an error longjmp in any way is protected by `lua_pcall`,
-and the user of the library is protected from directly interacting with unsafe things like the Lua stack,
-and there is overhead associated with this safety.
+One of `mlua`'s goals is to provide a *safe* API between Rust and Lua.
+Every place where the Lua C API may trigger an error longjmp is protected by `lua_pcall`,
+and the user of the library is protected from directly interacting with unsafe things like the Lua stack.
+There is overhead associated with this safety.
 
 Unfortunately, `mlua` does not provide absolute safety even without using `unsafe` .
 This library contains a huge amount of unsafe code. There are almost certainly bugs still lurking in this library!
@@ -240,8 +241,8 @@ It is surprisingly, fiendishly difficult to use the Lua C API without the potent
 
 ## Panic handling
 
-`mlua` wraps panics that are generated inside Rust callbacks in a regular Lua error. Panics could be
-resumed then by returning or propagating the Lua error to Rust code.
+`mlua` wraps panics that are generated inside Rust callbacks in a regular Lua error. Panics can then be
+resumed by returning or propagating the Lua error to Rust code.
 
 For example:
 ``` rust
@@ -260,12 +261,12 @@ let _ = lua.load(r#"
 unreachable!()
 ```
 
-Optionally `mlua` can disable Rust panics catching in Lua via `pcall`/`xpcall` and automatically resume
+Optionally, `mlua` can disable Rust panic catching in Lua via `pcall`/`xpcall` and automatically resume
 them across the Lua API boundary. This is controlled via `LuaOptions` and done by wrapping the Lua `pcall`/`xpcall`
-functions on a way to prevent catching errors that are wrapped Rust panics.
+functions to prevent catching errors that are wrapped Rust panics.
 
 `mlua` should also be panic safe in another way as well, which is that any `Lua` instances or handles
-remains usable after a user generated panic, and such panics should not break internal invariants or
+remain usable after a user generated panic, and such panics should not break internal invariants or
 leak Lua stack space. This is mostly important to safely use `mlua` types in Drop impls, as you should not be
 using panics for general error handling.
 
@@ -282,12 +283,12 @@ If you encounter them, a bug report would be very welcome:
 
 ## Sandboxing
 
-Please check the [Luau Sandboxing] page if you are interested in running untrusted Lua scripts in controlled environment.
+Please check the [Luau Sandboxing] page if you are interested in running untrusted Lua scripts in a controlled environment.
 
-`mlua` provides `Lua::sandbox` method for enabling sandbox mode (Luau only).
+`mlua` provides the `Lua::sandbox` method for enabling sandbox mode (Luau only).
 
-[Luau Sandboxing]: https://luau-lang.org/sandbox
+[Luau Sandboxing]: https://luau.org/sandbox
 
 ## License
 
-This project is licensed under the [MIT license](LICENSE)
+This project is licensed under the [MIT license](LICENSE).

docs/release_notes/v0.10.md

@@ -0,0 +1,195 @@
+## mlua v0.10 release notes
+
+The v0.10 version of mlua has goal to improve the user experience while keeping the same performance and safety guarantees.
+This document highlights the most notable features. For a full list of changes, see the [CHANGELOG].
+
+[CHANGELOG]: https://github.com/mlua-rs/mlua/blob/main/CHANGELOG.md
+
+### New features
+
+#### `'static` Lua types
+
+In previous mlua versions, it was required to have a `'lua` lifetime attached to every Lua value. v0.9 introduced (experimental) owned types that are `'static` without a lifetime attached, but they kept strong references to the Lua instance.
+In v0.10 all Lua types are `'static` and have only weak reference to the Lua instance. It means they are more flexible and can be used in more places without worrying about memory leaks.
+
+#### Truly `send` feature
+
+In this version Lua is `Send + Sync` when the `send` feature flag is enabled (previously was only `Send`). It means Lua instance and their values can be safely shared between threads and used in multi threaded async contexts.
+
+```rust
+let lua = Lua::new();
+
+lua.globals().set("i", 0)?;
+let func = lua.load("i = i + ...").into_function()?;
+
+std::thread::scope(|s| {
+    s.spawn(|| {
+        for i in 0..5 {
+            func.call::<()>(i).unwrap();
+        }
+    });
+    s.spawn(|| {
+        for i in 0..5 {
+            func.call::<()>(i).unwrap();
+        }
+    });
+});
+
+assert_eq!(lua.globals().get::<i32>("i")?, 20);
+```
+
+Under the hood, to synchronize access to the Lua state, mlua uses [`ReentrantMutex`] which can be recursively locked by a single thread. Only one thread can execute Lua code at a time, but it's possible to share Lua values between threads.
+
+This has some performance penalties (about 10-20%) compared to the lock free mode. This flag is disabled by default and does not supported in module mode.
+
+[`ReentrantMutex`]: https://docs.rs/parking_lot/latest/parking_lot/type.ReentrantMutex.html
+
+#### Register Rust functions with variable number of arguments
+
+The new traits `LuaNativeFn`/`LuaNativeFnMut`/`LuaNativeAsyncFn` have been introduced to provide a way to register Rust functions with variable number of arguments in Lua, without needing to pass all arguments as a tuple.
+
+They are used by `Function::wrap`/`Function::wrap_mut`/`Function::wrap_async` methods:
+
+```rust
+let add = Function::wrap(|a: i64, b: i64| Ok(a + b));
+
+lua.globals().set("add", add).unwrap();
+
+// Prints 50
+lua.load(r#"print(add(5, 45))"#).exec().unwrap();
+```
+
+To wrap functions that return direct value (non-`Result`) you can use `Function::wrap_raw` method.
+
+#### Setting metatable for Lua builtin types
+
+For Lua builtin types (like `string`, `function`, `number`, etc.) that have a shared metatable for all instances, it's now possible to set a custom metatable for them.
+
+```rust
+let mt = lua.create_table()?;
+mt.set("__tostring", lua.create_function(|_, b: bool| Ok(if b { "2" } else { "0" }))?)?;
+lua.set_type_metatable::<bool>(Some(mt));
+lua.load("assert(tostring(true) == '2')").exec().unwrap();
+```
+
+### Improvements
+
+#### New `ObjectLike` trait
+
+The `ObjectLike` trait is a combination of the `AnyUserDataExt` and `TableExt` traits used in previous versions. It provides a unified interface for working with Lua tables and userdata.
+
+#### `Either<L, R>` enum
+
+The `Either<L, R>` enum is a simple enum that can hold either `L` or `R` value. It's useful when you need to return or receive one of two types in a function.
+This type implements `IntoLua` and `FromLua` traits and can generate a meaningful error message when conversion fails.
+
+```rust
+let func = Function::wrap(|x: Either<i32, String>| Ok(format!("received: {x}")));
+
+lua.globals().set("func", func).unwrap();
+
+// Prints: received: 123
+lua.load(r#"print(func(123))"#).exec().unwrap();
+
+// Prints: bad argument #1: error converting Lua table to Either<i32, String>
+lua.load(r#"print(pcall(func, {}))"#).exec().unwrap();
+```
+
+#### `Lua::exec_raw` helper to execute low-level Lua C API code
+
+For advanced users, it's now possible to execute low-level Lua C API code using the `Lua::exec_raw` method.
+
+```rust
+let t = lua.create_sequence_from([1, 2, 3, 4, 5])?;
+let sum: i64 = unsafe {
+    lua.exec_raw(&t, |state| {
+        // top of the stack: table `t`
+        let mut sum = 0;
+        // push nil as the first key
+        mlua::ffi::lua_pushnil(state);
+        while mlua::ffi::lua_next(state, -2) != 0 {
+            sum += mlua::ffi::lua_tointeger(state, -1);
+            // Remove the value, keep the key for the next iteration
+            mlua::ffi::lua_pop(state, 1);
+        }
+        mlua::ffi::lua_pop(state, 1);
+        mlua::ffi::lua_pushinteger(state, sum);
+        // top of the stack: sum
+    })
+}?;
+assert_eq!(sum, 15);
+```
+
+The `exec_raw` method is longjmp-safe. It's not recommended to move `Drop` types into the closure to avoid possible memory leaks.
+
+#### `anyhow` feature flag
+
+The new `anyhow` feature flag adds `IntoLua` and `Into<mlua::Error>` implementation for the `anyhow::Error` type.
+
+```rust
+let f = lua.create_function(|_, ()| {
+    Err(anyhow!("error message"))?;
+    Ok(())
+})?;
+```
+
+### Breaking changes
+
+#### Scope changes
+
+The following `Scope` methods were changed:
+- Removed `Scope::create_any_userdata`
+- `Scope::create_nonstatic_userdata` is renamed to `Scope::create_userdata`
+
+Instead, scope has comprehensive support for borrowed userdata: `create_any_userdata_ref`, `create_any_userdata_ref_mut`, `create_userdata_ref`, `create_userdata_ref_mut`.
+
+`UserDataRef` and `UserDataRefMut` are no longer acceptable for scoped userdata access as they require owned underlying data.
+In mlua v0.9 this can cause read-after-free bug in some edge cases.
+
+To temporarily borrow underlying data, the `AnyUserData::borrow_scoped` and `AnyUserData::borrow_mut_scoped` methods were introduced:
+
+```rust
+let data = "hello".to_string();
+lua.scope(|scope| {
+    let ud = scope.create_any_userdata_ref(&data)?;
+
+    // We can only borrow scoped userdata using this method
+    ud.borrow_scoped::<String, ()>(|s| {
+        assert_eq!(s, "hello");
+    })?;
+
+    Ok(())
+})?;
+```
+
+Those methods work for scoped and regular userdata objects (but still require `T: 'static`).
+
+#### String changes
+
+Since `mlua::String` holds a weak reference to Lua without any guarantees about the lifetime of the underlying data, getting a `&str` or `&[u8]` from it is no longer safe.
+Lua instance can be destroyed while reference to the data is still alive:
+
+```rust
+let lua = Lua::new();
+let s: mlua::String = lua.create_string("hello, world")?; // only weak reference to Lua!
+let s_ref: &str = s.to_str()?; // this is not safe!
+drop(lua);
+println!("{s_ref}"); // use after free!
+```
+
+To solve this issue, return types of `mlua::String::to_str` and `mlua::String::as_bytes` methods changed to `BorrowedStr` and `BorrowedBytes` respectively.
+
+These new types hold a strong reference to the Lua instance and can be safely converted to `&str` or `&[u8]`:
+
+```rust
+let lua = Lua::new();
+let s: mlua::String = lua.create_string("hello, world")?;
+let s_ref: mlua::BorrowedStr = s.to_str()?; // The strong reference to Lua is held here
+drop(lua);
+println!("{s_ref}"); // ok
+```
+
+The good news is that `BorrowedStr` implements `Deref<Target = str>`/`AsRef<str>` as well as `Display`, `Debug`, `Eq`, `PartialEq` and other traits for easy usage.
+The same applies to `BorrowedBytes`.
+
+Unfortunately, `mlua::String::to_string_lossy` cannot return `Cow<'a, str>` anymore, because it requires a strong reference to Lua. It now returns Rust `String` instead.

docs/release_notes/v0.9.md

@@ -3,7 +3,7 @@
 The v0.9 version of mlua is a major release that includes a number of API changes and improvements. This release is a stepping stone towards the v1.0.
 This document highlights the most important changes. For a full list of changes, see the [CHANGELOG].
 
-[CHANGELOG]: https://github.com/khvzak/mlua/blob/main/CHANGELOG.md
+[CHANGELOG]: https://github.com/mlua-rs/mlua/blob/main/CHANGELOG.md
 
 ### New features
 
@@ -304,7 +304,7 @@ assert_eq!(f.call::<_, mlua::String>(())?, "hello");
 
 The new mlua version has a number of performance improvements. Please check the [benchmarks results] to see how mlua compares to rlua and rhai.
 
-[benchmarks results]: https://github.com/khvzak/script-bench-rs
+[benchmarks results]: https://github.com/mlua-rs/script-bench-rs
 
 ### Changes in `module` mode
 

mlua-sys/Cargo.toml

@@ -1,10 +1,10 @@
 [package]
 name = "mlua-sys"
-version = "0.6.3"
+version = "0.8.2"
 authors = ["Aleksandr Orlenko <zxteam@pm.me>"]
 rust-version = "1.71"
 edition = "2021"
-repository = "https://github.com/khvzak/mlua"
+repository = "https://github.com/mlua-rs/mlua"
 documentation = "https://docs.rs/mlua-sys"
 readme = "README.md"
 categories = ["external-ffi-bindings"]
@@ -12,7 +12,7 @@ license = "MIT"
 links = "lua"
 build = "build/main.rs"
 description = """
-Low level (FFI) bindings to Lua 5.4/5.3/5.2/5.1 (including LuaJIT) and Roblox Luau
+Low level (FFI) bindings to Lua 5.4/5.3/5.2/5.1 (including LuaJIT) and Luau
 """
 
 [package.metadata.docs.rs]
@@ -30,6 +30,7 @@ luau = ["luau0-src"]
 luau-codegen = ["luau"]
 luau-vector4 = ["luau"]
 vendored = ["lua-src", "luajit-src"]
+external = []
 module = []
 
 [dependencies]
@@ -38,9 +39,9 @@ module = []
 cc = "1.0"
 cfg-if = "1.0"
 pkg-config = "0.3.17"
-lua-src = { version = ">= 547.0.0, < 547.1.0", optional = true }
-luajit-src = { version = ">= 210.5.0, < 210.6.0", optional = true }
-luau0-src = { version = "0.10.0", optional = true }
+lua-src = { version = ">= 548.1.0, < 548.2.0", optional = true }
+luajit-src = { version = ">= 210.6.0, < 210.7.0", optional = true }
+luau0-src = { version = "0.15.4", optional = true }
 
 [lints.rust]
 unexpected_cfgs = { level = "allow", check-cfg = ['cfg(raw_dylib)'] }

mlua-sys/README.md

@@ -1,8 +1,8 @@
 # mlua-sys
 
-Low level (FFI) bindings to Lua 5.4/5.3/5.2/5.1 (including LuaJIT) and Roblox [Luau].
+Low level (FFI) bindings to Lua 5.4/5.3/5.2/5.1 (including LuaJIT) and [Luau].
 
 Intended to be consumed by the [mlua] crate.
 
-[Luau]: https://github.com/Roblox/luau
+[Luau]: https://github.com/luau-lang/luau
 [mlua]: https://crates.io/crates/mlua

mlua-sys/build/find_normal.rs

@@ -32,15 +32,19 @@ pub fn probe_lua() {
     // Find using `pkg-config`
 
     #[cfg(feature = "lua54")]
-    let (incl_bound, excl_bound, alt_probe, ver) = ("5.4", "5.5", Some("lua5.4"), "5.4");
+    let (incl_bound, excl_bound, alt_probe, ver) =
+        ("5.4", "5.5", ["lua5.4", "lua-5.4", "lua54"], "5.4");
     #[cfg(feature = "lua53")]
-    let (incl_bound, excl_bound, alt_probe, ver) = ("5.3", "5.4", Some("lua5.3"), "5.3");
+    let (incl_bound, excl_bound, alt_probe, ver) =
+        ("5.3", "5.4", ["lua5.3", "lua-5.3", "lua53"], "5.3");
     #[cfg(feature = "lua52")]
-    let (incl_bound, excl_bound, alt_probe, ver) = ("5.2", "5.3", Some("lua5.2"), "5.2");
+    let (incl_bound, excl_bound, alt_probe, ver) =
+        ("5.2", "5.3", ["lua5.2", "lua-5.2", "lua52"], "5.2");
     #[cfg(feature = "lua51")]
-    let (incl_bound, excl_bound, alt_probe, ver) = ("5.1", "5.2", Some("lua5.1"), "5.1");
+    let (incl_bound, excl_bound, alt_probe, ver) =
+        ("5.1", "5.2", ["lua5.1", "lua-5.1", "lua51"], "5.1");
     #[cfg(feature = "luajit")]
-    let (incl_bound, excl_bound, alt_probe, ver) = ("2.0.4", "2.2", None, "JIT");
+    let (incl_bound, excl_bound, alt_probe, ver) = ("2.0.4", "2.2", [], "JIT");
 
     #[rustfmt::skip]
     let mut lua = pkg_config::Config::new()
@@ -48,10 +52,16 @@ pub fn probe_lua() {
         .cargo_metadata(true)
         .probe(if cfg!(feature = "luajit") { "luajit" } else { "lua" });
 
-    if lua.is_err() && alt_probe.is_some() {
-        lua = pkg_config::Config::new()
-            .cargo_metadata(true)
-            .probe(alt_probe.unwrap());
+    if lua.is_err() {
+        for pkg in alt_probe {
+            lua = pkg_config::Config::new()
+                .cargo_metadata(true)
+                .probe(pkg);
+
+            if lua.is_ok() {
+                break;
+            }
+        }
     }
 
     lua.unwrap_or_else(|err| panic!("cannot find Lua{ver} using `pkg-config`: {err}"));

mlua-sys/build/main_inner.rs

@@ -14,22 +14,29 @@ fn main() {
     #[cfg(all(feature = "luau", feature = "module", windows))]
     compile_error!("Luau does not support `module` mode on Windows");
 
-    #[cfg(all(feature = "module", feature = "vendored"))]
-    compile_error!("`vendored` and `module` features are mutually exclusive");
+    #[cfg(any(
+        all(feature = "vendored", any(feature = "external", feature = "module")),
+        all(feature = "external", any(feature = "vendored", feature = "module")),
+        all(feature = "module", any(feature = "vendored", feature = "external"))
+    ))]
+    compile_error!("`vendored`, `external` and `module` features are mutually exclusive");
 
     println!("cargo:rerun-if-changed=build");
 
-    let target_os = env::var("CARGO_CFG_TARGET_OS").unwrap();
-    if target_os == "windows" && cfg!(feature = "module") {
-        if !std::env::var("LUA_LIB_NAME").unwrap_or_default().is_empty() {
-            // Don't use raw-dylib linking
-            find::probe_lua();
-            return;
+    // Check if compilation and linking is handled by external crate
+    if cfg!(not(feature = "external")) {
+        let target_os = env::var("CARGO_CFG_TARGET_OS").unwrap();
+        if target_os == "windows" && cfg!(feature = "module") {
+            if !std::env::var("LUA_LIB_NAME").unwrap_or_default().is_empty() {
+                // Don't use raw-dylib linking
+                find::probe_lua();
+                return;
+            }
+
+            println!("cargo:rustc-cfg=raw_dylib");
         }
 
-        println!("cargo:rustc-cfg=raw_dylib");
+        #[cfg(not(feature = "module"))]
+        find::probe_lua();
     }
-
-    #[cfg(not(feature = "module"))]
-    find::probe_lua();
 }

mlua-sys/src/lib.rs

@@ -1,7 +1,8 @@
-//! Low level bindings to Lua 5.4/5.3/5.2/5.1 (including LuaJIT) and Roblox Luau.
+//! Low level bindings to Lua 5.4/5.3/5.2/5.1 (including LuaJIT) and Luau.
 
-#![allow(non_camel_case_types, non_snake_case, dead_code)]
+#![allow(non_camel_case_types, non_snake_case)]
 #![allow(clippy::missing_safety_doc)]
+#![allow(unsafe_op_in_unsafe_fn)]
 #![doc(test(attr(deny(warnings))))]
 #![cfg_attr(docsrs, feature(doc_cfg))]
 

mlua-sys/src/lua51/compat.rs

@@ -90,7 +90,7 @@ unsafe fn compat53_findfield(L: *mut lua_State, objidx: c_int, level: c_int) ->
             } else if compat53_findfield(L, objidx, level - 1) != 0 {
                 // try recursively
                 lua_remove(L, -2); // remove table (but keep name)
-                lua_pushliteral(L, ".");
+                lua_pushliteral(L, c".");
                 lua_insert(L, -2); // place '.' between the two names
                 lua_concat(L, 3);
                 return 1;
@@ -121,13 +121,13 @@ unsafe fn compat53_pushfuncname(L: *mut lua_State, ar: *mut lua_Debug) {
         lua_pushfstring(L, cstr!("function '%s'"), (*ar).name);
     } else if *(*ar).what == b'm' as c_char {
         // main?
-        lua_pushliteral(L, "main chunk");
+        lua_pushliteral(L, c"main chunk");
     } else if *(*ar).what == b'C' as c_char {
         if compat53_pushglobalfuncname(L, ar) != 0 {
             lua_pushfstring(L, cstr!("function '%s'"), lua_tostring(L, -1));
             lua_remove(L, -2); // remove name
         } else {
-            lua_pushliteral(L, "?");
+            lua_pushliteral(L, c"?");
         }
     } else {
         lua_pushfstring(
@@ -176,7 +176,7 @@ pub unsafe fn lua_rotate(L: *mut lua_State, mut idx: c_int, mut n: c_int) {
 #[inline(always)]
 pub unsafe fn lua_copy(L: *mut lua_State, fromidx: c_int, toidx: c_int) {
     let abs_to = lua_absindex(L, toidx);
-    luaL_checkstack(L, 1, cstr!("not enough stack slots"));
+    luaL_checkstack(L, 1, cstr!("not enough stack slots available"));
     lua_pushvalue(L, fromidx);
     lua_replace(L, abs_to);
 }
@@ -314,7 +314,7 @@ pub unsafe fn lua_rawseti(L: *mut lua_State, idx: c_int, n: lua_Integer) {
 #[inline(always)]
 pub unsafe fn lua_rawsetp(L: *mut lua_State, idx: c_int, p: *const c_void) {
     let abs_i = lua_absindex(L, idx);
-    luaL_checkstack(L, 1, cstr!("not enough stack slots"));
+    luaL_checkstack(L, 1, cstr!("not enough stack slots available"));
     lua_pushlightuserdata(L, p as *mut c_void);
     lua_insert(L, -2);
     lua_rawset(L, abs_i);
@@ -377,7 +377,7 @@ pub unsafe fn luaL_checkstack(L: *mut lua_State, sz: c_int, msg: *const c_char)
         if !msg.is_null() {
             luaL_error(L, cstr!("stack overflow (%s)"), msg);
         } else {
-            lua_pushliteral(L, "stack overflow");
+            lua_pushliteral(L, c"stack overflow");
             lua_error(L);
         }
     }
@@ -444,7 +444,7 @@ pub unsafe fn luaL_loadbufferx(
 #[inline(always)]
 pub unsafe fn luaL_len(L: *mut lua_State, idx: c_int) -> lua_Integer {
     let mut isnum = 0;
-    luaL_checkstack(L, 1, cstr!("not enough stack slots"));
+    luaL_checkstack(L, 1, cstr!("not enough stack slots available"));
     lua_len(L, idx);
     let res = lua_tointegerx(L, -1, &mut isnum);
     lua_pop(L, 1);
@@ -467,12 +467,12 @@ pub unsafe fn luaL_traceback(L: *mut lua_State, L1: *mut lua_State, msg: *const
     if !msg.is_null() {
         lua_pushfstring(L, cstr!("%s\n"), msg);
     }
-    lua_pushliteral(L, "stack traceback:");
+    lua_pushliteral(L, c"stack traceback:");
     while lua_getstack(L1, level, &mut ar) != 0 {
         level += 1;
         if level == mark {
             // too many levels?
-            lua_pushliteral(L, "\n\t..."); // add a '...'
+            lua_pushliteral(L, c"\n\t..."); // add a '...'
             level = numlevels - COMPAT53_LEVELS2; // and skip to last ones
         } else {
             lua_getinfo(L1, cstr!("Slnt"), &mut ar);
@@ -480,7 +480,7 @@ pub unsafe fn luaL_traceback(L: *mut lua_State, L1: *mut lua_State, msg: *const
             if ar.currentline > 0 {
                 lua_pushfstring(L, cstr!("%d:"), ar.currentline);
             }
-            lua_pushliteral(L, " in ");
+            lua_pushliteral(L, c" in ");
             compat53_pushfuncname(L, &mut ar);
             lua_concat(L, lua_gettop(L) - top);
         }
@@ -493,16 +493,16 @@ pub unsafe fn luaL_tolstring(L: *mut lua_State, mut idx: c_int, len: *mut usize)
     if luaL_callmeta(L, idx, cstr!("__tostring")) == 0 {
         match lua_type(L, idx) {
             LUA_TNIL => {
-                lua_pushliteral(L, "nil");
+                lua_pushliteral(L, c"nil");
             }
             LUA_TSTRING | LUA_TNUMBER => {
                 lua_pushvalue(L, idx);
             }
             LUA_TBOOLEAN => {
                 if lua_toboolean(L, idx) == 0 {
-                    lua_pushliteral(L, "false");
+                    lua_pushliteral(L, c"false");
                 } else {
-                    lua_pushliteral(L, "true");
+                    lua_pushliteral(L, c"true");
                 }
             }
             t => {
@@ -526,14 +526,14 @@ pub unsafe fn luaL_tolstring(L: *mut lua_State, mut idx: c_int, len: *mut usize)
 
 #[inline(always)]
 pub unsafe fn luaL_setmetatable(L: *mut lua_State, tname: *const c_char) {
-    luaL_checkstack(L, 1, cstr!("not enough stack slots"));
+    luaL_checkstack(L, 1, cstr!("not enough stack slots available"));
     luaL_getmetatable(L, tname);
     lua_setmetatable(L, -2);
 }
 
 pub unsafe fn luaL_getsubtable(L: *mut lua_State, idx: c_int, fname: *const c_char) -> c_int {
     let abs_i = lua_absindex(L, idx);
-    luaL_checkstack(L, 3, cstr!("not enough stack slots"));
+    luaL_checkstack(L, 3, cstr!("not enough stack slots available"));
     lua_pushstring_(L, fname);
     if lua_gettable(L, abs_i) == LUA_TTABLE {
         return 1;
@@ -548,7 +548,7 @@ pub unsafe fn luaL_getsubtable(L: *mut lua_State, idx: c_int, fname: *const c_ch
 
 pub unsafe fn luaL_requiref(L: *mut lua_State, modname: *const c_char, openf: lua_CFunction, glb: c_int) {
     luaL_checkstack(L, 3, cstr!("not enough stack slots available"));
-    luaL_getsubtable(L, LUA_REGISTRYINDEX, cstr!("_LOADED"));
+    luaL_getsubtable(L, LUA_REGISTRYINDEX, LUA_LOADED_TABLE);
     if lua_getfield(L, -1, modname) == LUA_TNIL {
         lua_pop(L, 1);
         lua_pushcfunction(L, openf);

mlua-sys/src/lua51/lauxlib.rs

@@ -8,6 +8,9 @@ use super::lua::{self, lua_CFunction, lua_Integer, lua_Number, lua_State};
 // Extra error code for 'luaL_load'
 pub const LUA_ERRFILE: c_int = lua::LUA_ERRERR + 1;
 
+// Key, in the registry, for table of loaded modules
+pub const LUA_LOADED_TABLE: *const c_char = cstr!("_LOADED");
+
 #[repr(C)]
 pub struct luaL_Reg {
     pub name: *const c_char,
@@ -15,7 +18,7 @@ pub struct luaL_Reg {
 }
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua51", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn luaL_register(L: *mut lua_State, libname: *const c_char, l: *const luaL_Reg);
     #[link_name = "luaL_getmetafield"]
     pub fn luaL_getmetafield_(L: *mut lua_State, obj: c_int, e: *const c_char) -> c_int;
@@ -58,7 +61,7 @@ pub const LUA_NOREF: c_int = -2;
 pub const LUA_REFNIL: c_int = -1;
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua51", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn luaL_ref(L: *mut lua_State, t: c_int) -> c_int;
     pub fn luaL_unref(L: *mut lua_State, t: c_int, r#ref: c_int);
 

mlua-sys/src/lua51/lua.rs

@@ -1,5 +1,6 @@
 //! Contains definitions from `lua.h`.
 
+use std::ffi::CStr;
 use std::marker::{PhantomData, PhantomPinned};
 use std::os::raw::{c_char, c_double, c_int, c_void};
 use std::ptr;
@@ -83,13 +84,13 @@ pub type lua_Reader =
 pub type lua_Writer =
     unsafe extern "C-unwind" fn(L: *mut lua_State, p: *const c_void, sz: usize, ud: *mut c_void) -> c_int;
 
-/// Type for memory-allocation functions
+/// Type for memory-allocation functions (no unwinding)
 #[rustfmt::skip]
 pub type lua_Alloc =
-    unsafe extern "C-unwind" fn(ud: *mut c_void, ptr: *mut c_void, osize: usize, nsize: usize) -> *mut c_void;
+    unsafe extern "C" fn(ud: *mut c_void, ptr: *mut c_void, osize: usize, nsize: usize) -> *mut c_void;
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua51", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     //
     // State manipulation
     //
@@ -219,7 +220,7 @@ pub const LUA_GCSETPAUSE: c_int = 6;
 pub const LUA_GCSETSTEPMUL: c_int = 7;
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua51", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn lua_gc(L: *mut lua_State, what: c_int, data: c_int) -> c_int;
 }
 
@@ -227,7 +228,7 @@ extern "C-unwind" {
 // Miscellaneous functions
 //
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua51", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     #[link_name = "lua_error"]
     fn lua_error_(L: *mut lua_State) -> c_int;
     pub fn lua_next(L: *mut lua_State, idx: c_int) -> c_int;
@@ -312,10 +313,8 @@ pub unsafe fn lua_isnoneornil(L: *mut lua_State, n: c_int) -> c_int {
 }
 
 #[inline(always)]
-pub unsafe fn lua_pushliteral(L: *mut lua_State, s: &'static str) {
-    use std::ffi::CString;
-    let c_str = CString::new(s).unwrap();
-    lua_pushlstring_(L, c_str.as_ptr(), c_str.as_bytes().len())
+pub unsafe fn lua_pushliteral(L: *mut lua_State, s: &'static CStr) {
+    lua_pushstring_(L, s.as_ptr());
 }
 
 #[inline(always)]
@@ -371,7 +370,7 @@ pub const LUA_MASKCOUNT: c_int = 1 << (LUA_HOOKCOUNT as usize);
 pub type lua_Hook = unsafe extern "C-unwind" fn(L: *mut lua_State, ar: *mut lua_Debug);
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua51", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn lua_getstack(L: *mut lua_State, level: c_int, ar: *mut lua_Debug) -> c_int;
     pub fn lua_getinfo(L: *mut lua_State, what: *const c_char, ar: *mut lua_Debug) -> c_int;
     pub fn lua_getlocal(L: *mut lua_State, ar: *const lua_Debug, n: c_int) -> *const c_char;

mlua-sys/src/lua51/lualib.rs

@@ -1,27 +1,27 @@
 //! Contains definitions from `lualib.h`.
 
-use std::os::raw::c_int;
+use std::os::raw::{c_char, c_int};
 
 use super::lua::lua_State;
 
-pub const LUA_COLIBNAME: &str = "coroutine";
-pub const LUA_TABLIBNAME: &str = "table";
-pub const LUA_IOLIBNAME: &str = "io";
-pub const LUA_OSLIBNAME: &str = "os";
-pub const LUA_STRLIBNAME: &str = "string";
-pub const LUA_MATHLIBNAME: &str = "math";
-pub const LUA_DBLIBNAME: &str = "debug";
-pub const LUA_LOADLIBNAME: &str = "package";
+pub const LUA_COLIBNAME: *const c_char = cstr!("coroutine");
+pub const LUA_TABLIBNAME: *const c_char = cstr!("table");
+pub const LUA_IOLIBNAME: *const c_char = cstr!("io");
+pub const LUA_OSLIBNAME: *const c_char = cstr!("os");
+pub const LUA_STRLIBNAME: *const c_char = cstr!("string");
+pub const LUA_MATHLIBNAME: *const c_char = cstr!("math");
+pub const LUA_DBLIBNAME: *const c_char = cstr!("debug");
+pub const LUA_LOADLIBNAME: *const c_char = cstr!("package");
 
 #[cfg(feature = "luajit")]
-pub const LUA_BITLIBNAME: &str = "bit";
+pub const LUA_BITLIBNAME: *const c_char = cstr!("bit");
 #[cfg(feature = "luajit")]
-pub const LUA_JITLIBNAME: &str = "jit";
+pub const LUA_JITLIBNAME: *const c_char = cstr!("jit");
 #[cfg(feature = "luajit")]
-pub const LUA_FFILIBNAME: &str = "ffi";
+pub const LUA_FFILIBNAME: *const c_char = cstr!("ffi");
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua51", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn luaopen_base(L: *mut lua_State) -> c_int;
     pub fn luaopen_table(L: *mut lua_State) -> c_int;
     pub fn luaopen_io(L: *mut lua_State) -> c_int;

mlua-sys/src/lua52/compat.rs

@@ -199,16 +199,16 @@ pub unsafe fn luaL_tolstring(L: *mut lua_State, mut idx: c_int, len: *mut usize)
     if luaL_callmeta(L, idx, cstr!("__tostring")) == 0 {
         match lua_type(L, idx) {
             LUA_TNIL => {
-                lua_pushliteral(L, "nil");
+                lua_pushliteral(L, c"nil");
             }
             LUA_TSTRING | LUA_TNUMBER => {
                 lua_pushvalue(L, idx);
             }
             LUA_TBOOLEAN => {
                 if lua_toboolean(L, idx) == 0 {
-                    lua_pushliteral(L, "false");
+                    lua_pushliteral(L, c"false");
                 } else {
-                    lua_pushliteral(L, "true");
+                    lua_pushliteral(L, c"true");
                 }
             }
             t => {
@@ -232,7 +232,7 @@ pub unsafe fn luaL_tolstring(L: *mut lua_State, mut idx: c_int, len: *mut usize)
 
 pub unsafe fn luaL_requiref(L: *mut lua_State, modname: *const c_char, openf: lua_CFunction, glb: c_int) {
     luaL_checkstack(L, 3, cstr!("not enough stack slots available"));
-    luaL_getsubtable(L, LUA_REGISTRYINDEX, cstr!("_LOADED"));
+    luaL_getsubtable(L, LUA_REGISTRYINDEX, LUA_LOADED_TABLE);
     if lua_getfield(L, -1, modname) == LUA_TNIL {
         lua_pop(L, 1);
         lua_pushcfunction(L, openf);

mlua-sys/src/lua52/lauxlib.rs

@@ -8,6 +8,12 @@ use super::lua::{self, lua_CFunction, lua_Integer, lua_Number, lua_State, lua_Un
 // Extra error code for 'luaL_load'
 pub const LUA_ERRFILE: c_int = lua::LUA_ERRERR + 1;
 
+// Key, in the registry, for table of loaded modules
+pub const LUA_LOADED_TABLE: *const c_char = cstr!("_LOADED");
+
+// Key, in the registry, for table of preloaded loaders
+pub const LUA_PRELOAD_TABLE: *const c_char = cstr!("_PRELOAD");
+
 #[repr(C)]
 pub struct luaL_Reg {
     pub name: *const c_char,
@@ -15,7 +21,7 @@ pub struct luaL_Reg {
 }
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua52", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn luaL_checkversion_(L: *mut lua_State, ver: lua_Number);
 
     #[link_name = "luaL_getmetafield"]
@@ -63,7 +69,7 @@ pub const LUA_NOREF: c_int = -2;
 pub const LUA_REFNIL: c_int = -1;
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua52", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn luaL_ref(L: *mut lua_State, t: c_int) -> c_int;
     pub fn luaL_unref(L: *mut lua_State, t: c_int, r#ref: c_int);
 
@@ -76,7 +82,7 @@ pub unsafe fn luaL_loadfile(L: *mut lua_State, f: *const c_char) -> c_int {
 }
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua52", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn luaL_loadbufferx(
         L: *mut lua_State,
         buff: *const c_char,

mlua-sys/src/lua52/lua.rs

@@ -1,5 +1,6 @@
 //! Contains definitions from `lua.h`.
 
+use std::ffi::CStr;
 use std::marker::{PhantomData, PhantomPinned};
 use std::os::raw::{c_char, c_double, c_int, c_uchar, c_uint, c_void};
 use std::ptr;
@@ -88,13 +89,13 @@ pub type lua_Reader =
 pub type lua_Writer =
     unsafe extern "C-unwind" fn(L: *mut lua_State, p: *const c_void, sz: usize, ud: *mut c_void) -> c_int;
 
-/// Type for memory-allocation functions
+/// Type for memory-allocation functions (no unwinding)
 #[rustfmt::skip]
 pub type lua_Alloc =
-    unsafe extern "C-unwind" fn(ud: *mut c_void, ptr: *mut c_void, osize: usize, nsize: usize) -> *mut c_void;
+    unsafe extern "C" fn(ud: *mut c_void, ptr: *mut c_void, osize: usize, nsize: usize) -> *mut c_void;
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua52", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     //
     // State manipulation
     //
@@ -160,14 +161,14 @@ pub const LUA_OPLT: c_int = 1;
 pub const LUA_OPLE: c_int = 2;
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua52", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn lua_arith(L: *mut lua_State, op: c_int);
     pub fn lua_rawequal(L: *mut lua_State, idx1: c_int, idx2: c_int) -> c_int;
     pub fn lua_compare(L: *mut lua_State, idx1: c_int, idx2: c_int, op: c_int) -> c_int;
 }
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua52", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     //
     // Push functions (C -> stack)
     //
@@ -256,7 +257,7 @@ pub unsafe fn lua_pcall(L: *mut lua_State, n: c_int, r: c_int, f: c_int) -> c_in
 }
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua52", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     //
     // Coroutine functions
     //
@@ -288,12 +289,12 @@ pub const LUA_GCGEN: c_int = 10;
 pub const LUA_GCINC: c_int = 11;
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua52", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn lua_gc(L: *mut lua_State, what: c_int, data: c_int) -> c_int;
 }
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua52", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     //
     // Miscellaneous functions
     //
@@ -395,10 +396,8 @@ pub unsafe fn lua_isnoneornil(L: *mut lua_State, n: c_int) -> c_int {
 }
 
 #[inline(always)]
-pub unsafe fn lua_pushliteral(L: *mut lua_State, s: &'static str) -> *const c_char {
-    use std::ffi::CString;
-    let c_str = CString::new(s).unwrap();
-    lua_pushlstring_(L, c_str.as_ptr(), c_str.as_bytes().len())
+pub unsafe fn lua_pushliteral(L: *mut lua_State, s: &'static CStr) {
+    lua_pushstring(L, s.as_ptr());
 }
 
 #[inline(always)]
@@ -449,7 +448,7 @@ pub const LUA_MASKCOUNT: c_int = 1 << (LUA_HOOKCOUNT as usize);
 pub type lua_Hook = unsafe extern "C-unwind" fn(L: *mut lua_State, ar: *mut lua_Debug);
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua52", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn lua_getstack(L: *mut lua_State, level: c_int, ar: *mut lua_Debug) -> c_int;
     pub fn lua_getinfo(L: *mut lua_State, what: *const c_char, ar: *mut lua_Debug) -> c_int;
     pub fn lua_getlocal(L: *mut lua_State, ar: *const lua_Debug, n: c_int) -> *const c_char;

mlua-sys/src/lua52/lualib.rs

@@ -1,21 +1,21 @@
 //! Contains definitions from `lualib.h`.
 
-use std::os::raw::c_int;
+use std::os::raw::{c_char, c_int};
 
 use super::lua::lua_State;
 
-pub const LUA_COLIBNAME: &str = "coroutine";
-pub const LUA_TABLIBNAME: &str = "table";
-pub const LUA_IOLIBNAME: &str = "io";
-pub const LUA_OSLIBNAME: &str = "os";
-pub const LUA_STRLIBNAME: &str = "string";
-pub const LUA_BITLIBNAME: &str = "bit32";
-pub const LUA_MATHLIBNAME: &str = "math";
-pub const LUA_DBLIBNAME: &str = "debug";
-pub const LUA_LOADLIBNAME: &str = "package";
+pub const LUA_COLIBNAME: *const c_char = cstr!("coroutine");
+pub const LUA_TABLIBNAME: *const c_char = cstr!("table");
+pub const LUA_IOLIBNAME: *const c_char = cstr!("io");
+pub const LUA_OSLIBNAME: *const c_char = cstr!("os");
+pub const LUA_STRLIBNAME: *const c_char = cstr!("string");
+pub const LUA_BITLIBNAME: *const c_char = cstr!("bit32");
+pub const LUA_MATHLIBNAME: *const c_char = cstr!("math");
+pub const LUA_DBLIBNAME: *const c_char = cstr!("debug");
+pub const LUA_LOADLIBNAME: *const c_char = cstr!("package");
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua52", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn luaopen_base(L: *mut lua_State) -> c_int;
     pub fn luaopen_coroutine(L: *mut lua_State) -> c_int;
     pub fn luaopen_table(L: *mut lua_State) -> c_int;

mlua-sys/src/lua53/lauxlib.rs

@@ -9,10 +9,10 @@ use super::lua::{self, lua_CFunction, lua_Integer, lua_Number, lua_State};
 pub const LUA_ERRFILE: c_int = lua::LUA_ERRERR + 1;
 
 // Key, in the registry, for table of loaded modules
-pub const LUA_LOADED_TABLE: &str = "_LOADED";
+pub const LUA_LOADED_TABLE: *const c_char = cstr!("_LOADED");
 
 // Key, in the registry, for table of preloaded loaders
-pub const LUA_PRELOAD_TABLE: &str = "_PRELOAD";
+pub const LUA_PRELOAD_TABLE: *const c_char = cstr!("_PRELOAD");
 
 #[repr(C)]
 pub struct luaL_Reg {
@@ -21,7 +21,7 @@ pub struct luaL_Reg {
 }
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua53", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn luaL_checkversion_(L: *mut lua_State, ver: lua_Number, sz: usize);
 
     pub fn luaL_getmetafield(L: *mut lua_State, obj: c_int, e: *const c_char) -> c_int;
@@ -65,7 +65,7 @@ pub const LUA_NOREF: c_int = -2;
 pub const LUA_REFNIL: c_int = -1;
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua53", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn luaL_ref(L: *mut lua_State, t: c_int) -> c_int;
     pub fn luaL_unref(L: *mut lua_State, t: c_int, r#ref: c_int);
 
@@ -78,7 +78,7 @@ pub unsafe fn luaL_loadfile(L: *mut lua_State, f: *const c_char) -> c_int {
 }
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua53", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn luaL_loadbufferx(
         L: *mut lua_State,
         buff: *const c_char,

mlua-sys/src/lua53/lua.rs

@@ -1,5 +1,6 @@
 //! Contains definitions from `lua.h`.
 
+use std::ffi::CStr;
 use std::marker::{PhantomData, PhantomPinned};
 use std::os::raw::{c_char, c_double, c_int, c_uchar, c_void};
 use std::{mem, ptr};
@@ -95,13 +96,13 @@ pub type lua_Reader =
 pub type lua_Writer =
     unsafe extern "C-unwind" fn(L: *mut lua_State, p: *const c_void, sz: usize, ud: *mut c_void) -> c_int;
 
-/// Type for memory-allocation functions
+/// Type for memory-allocation functions (no unwinding)
 #[rustfmt::skip]
 pub type lua_Alloc =
-    unsafe extern "C-unwind" fn(ud: *mut c_void, ptr: *mut c_void, osize: usize, nsize: usize) -> *mut c_void;
+    unsafe extern "C" fn(ud: *mut c_void, ptr: *mut c_void, osize: usize, nsize: usize) -> *mut c_void;
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua53", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     //
     // State manipulation
     //
@@ -171,14 +172,14 @@ pub const LUA_OPLT: c_int = 1;
 pub const LUA_OPLE: c_int = 2;
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua53", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn lua_arith(L: *mut lua_State, op: c_int);
     pub fn lua_rawequal(L: *mut lua_State, idx1: c_int, idx2: c_int) -> c_int;
     pub fn lua_compare(L: *mut lua_State, idx1: c_int, idx2: c_int, op: c_int) -> c_int;
 }
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua53", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     //
     // Push functions (C -> stack)
     //
@@ -264,7 +265,7 @@ pub unsafe fn lua_pcall(L: *mut lua_State, n: c_int, r: c_int, f: c_int) -> c_in
 }
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua53", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     //
     // Coroutine functions
     //
@@ -299,12 +300,12 @@ pub const LUA_GCSETSTEPMUL: c_int = 7;
 pub const LUA_GCISRUNNING: c_int = 9;
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua53", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn lua_gc(L: *mut lua_State, what: c_int, data: c_int) -> c_int;
 }
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua53", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     //
     // Miscellaneous functions
     //
@@ -407,10 +408,8 @@ pub unsafe fn lua_isnoneornil(L: *mut lua_State, n: c_int) -> c_int {
 }
 
 #[inline(always)]
-pub unsafe fn lua_pushliteral(L: *mut lua_State, s: &'static str) -> *const c_char {
-    use std::ffi::CString;
-    let c_str = CString::new(s).unwrap();
-    lua_pushlstring(L, c_str.as_ptr(), c_str.as_bytes().len())
+pub unsafe fn lua_pushliteral(L: *mut lua_State, s: &'static CStr) {
+    lua_pushstring(L, s.as_ptr());
 }
 
 #[inline(always)]
@@ -478,7 +477,7 @@ pub const LUA_MASKCOUNT: c_int = 1 << (LUA_HOOKCOUNT as usize);
 pub type lua_Hook = unsafe extern "C-unwind" fn(L: *mut lua_State, ar: *mut lua_Debug);
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua53", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn lua_getstack(L: *mut lua_State, level: c_int, ar: *mut lua_Debug) -> c_int;
     pub fn lua_getinfo(L: *mut lua_State, what: *const c_char, ar: *mut lua_Debug) -> c_int;
     pub fn lua_getlocal(L: *mut lua_State, ar: *const lua_Debug, n: c_int) -> *const c_char;

mlua-sys/src/lua53/lualib.rs

@@ -1,22 +1,22 @@
 //! Contains definitions from `lualib.h`.
 
-use std::os::raw::c_int;
+use std::os::raw::{c_char, c_int};
 
 use super::lua::lua_State;
 
-pub const LUA_COLIBNAME: &str = "coroutine";
-pub const LUA_TABLIBNAME: &str = "table";
-pub const LUA_IOLIBNAME: &str = "io";
-pub const LUA_OSLIBNAME: &str = "os";
-pub const LUA_STRLIBNAME: &str = "string";
-pub const LUA_UTF8LIBNAME: &str = "utf8";
-pub const LUA_BITLIBNAME: &str = "bit32";
-pub const LUA_MATHLIBNAME: &str = "math";
-pub const LUA_DBLIBNAME: &str = "debug";
-pub const LUA_LOADLIBNAME: &str = "package";
+pub const LUA_COLIBNAME: *const c_char = cstr!("coroutine");
+pub const LUA_TABLIBNAME: *const c_char = cstr!("table");
+pub const LUA_IOLIBNAME: *const c_char = cstr!("io");
+pub const LUA_OSLIBNAME: *const c_char = cstr!("os");
+pub const LUA_STRLIBNAME: *const c_char = cstr!("string");
+pub const LUA_UTF8LIBNAME: *const c_char = cstr!("utf8");
+pub const LUA_BITLIBNAME: *const c_char = cstr!("bit32");
+pub const LUA_MATHLIBNAME: *const c_char = cstr!("math");
+pub const LUA_DBLIBNAME: *const c_char = cstr!("debug");
+pub const LUA_LOADLIBNAME: *const c_char = cstr!("package");
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua53", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn luaopen_base(L: *mut lua_State) -> c_int;
     pub fn luaopen_coroutine(L: *mut lua_State) -> c_int;
     pub fn luaopen_table(L: *mut lua_State) -> c_int;

mlua-sys/src/lua54/lauxlib.rs

@@ -9,10 +9,10 @@ use super::lua::{self, lua_CFunction, lua_Integer, lua_Number, lua_State};
 pub const LUA_ERRFILE: c_int = lua::LUA_ERRERR + 1;
 
 // Key, in the registry, for table of loaded modules
-pub const LUA_LOADED_TABLE: &str = "_LOADED";
+pub const LUA_LOADED_TABLE: *const c_char = cstr!("_LOADED");
 
 // Key, in the registry, for table of preloaded loaders
-pub const LUA_PRELOAD_TABLE: &str = "_PRELOAD";
+pub const LUA_PRELOAD_TABLE: *const c_char = cstr!("_PRELOAD");
 
 #[repr(C)]
 pub struct luaL_Reg {
@@ -21,7 +21,7 @@ pub struct luaL_Reg {
 }
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua54", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn luaL_checkversion_(L: *mut lua_State, ver: lua_Number, sz: usize);
 
     pub fn luaL_getmetafield(L: *mut lua_State, obj: c_int, e: *const c_char) -> c_int;
@@ -64,7 +64,7 @@ pub const LUA_NOREF: c_int = -2;
 pub const LUA_REFNIL: c_int = -1;
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua54", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn luaL_ref(L: *mut lua_State, t: c_int) -> c_int;
     pub fn luaL_unref(L: *mut lua_State, t: c_int, r#ref: c_int);
 
@@ -77,7 +77,7 @@ pub unsafe fn luaL_loadfile(L: *mut lua_State, f: *const c_char) -> c_int {
 }
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua54", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn luaL_loadbufferx(
         L: *mut lua_State,
         buff: *const c_char,

mlua-sys/src/lua54/lua.rs

@@ -1,5 +1,6 @@
 //! Contains definitions from `lua.h`.
 
+use std::ffi::CStr;
 use std::marker::{PhantomData, PhantomPinned};
 use std::os::raw::{c_char, c_double, c_int, c_uchar, c_ushort, c_void};
 use std::{mem, ptr};
@@ -94,16 +95,16 @@ pub type lua_Reader =
 pub type lua_Writer =
     unsafe extern "C-unwind" fn(L: *mut lua_State, p: *const c_void, sz: usize, ud: *mut c_void) -> c_int;
 
-/// Type for memory-allocation functions
+/// Type for memory-allocation functions (no unwinding)
 #[rustfmt::skip]
 pub type lua_Alloc =
-    unsafe extern "C-unwind" fn(ud: *mut c_void, ptr: *mut c_void, osize: usize, nsize: usize) -> *mut c_void;
+    unsafe extern "C" fn(ud: *mut c_void, ptr: *mut c_void, osize: usize, nsize: usize) -> *mut c_void;
 
 /// Type for warning functions
 pub type lua_WarnFunction = unsafe extern "C-unwind" fn(ud: *mut c_void, msg: *const c_char, tocont: c_int);
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua54", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     //
     // State manipulation
     //
@@ -185,14 +186,14 @@ pub const LUA_OPLT: c_int = 1;
 pub const LUA_OPLE: c_int = 2;
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua54", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn lua_arith(L: *mut lua_State, op: c_int);
     pub fn lua_rawequal(L: *mut lua_State, idx1: c_int, idx2: c_int) -> c_int;
     pub fn lua_compare(L: *mut lua_State, idx1: c_int, idx2: c_int, op: c_int) -> c_int;
 }
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua54", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     //
     // Push functions (C -> stack)
     //
@@ -278,7 +279,7 @@ pub unsafe fn lua_pcall(L: *mut lua_State, n: c_int, r: c_int, f: c_int) -> c_in
 }
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua54", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     //
     // Coroutine functions
     //
@@ -302,7 +303,7 @@ pub unsafe fn lua_yield(L: *mut lua_State, n: c_int) -> c_int {
 // Warning-related functions
 //
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua54", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn lua_setwarnf(L: *mut lua_State, f: Option<lua_WarnFunction>, ud: *mut c_void);
     pub fn lua_warning(L: *mut lua_State, msg: *const c_char, tocont: c_int);
 }
@@ -323,12 +324,12 @@ pub const LUA_GCGEN: c_int = 10;
 pub const LUA_GCINC: c_int = 11;
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua54", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn lua_gc(L: *mut lua_State, what: c_int, ...) -> c_int;
 }
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua54", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     //
     // Miscellaneous functions
     //
@@ -434,10 +435,8 @@ pub unsafe fn lua_isnoneornil(L: *mut lua_State, n: c_int) -> c_int {
 }
 
 #[inline(always)]
-pub unsafe fn lua_pushliteral(L: *mut lua_State, s: &'static str) -> *const c_char {
-    use std::ffi::CString;
-    let c_str = CString::new(s).unwrap();
-    lua_pushlstring(L, c_str.as_ptr(), c_str.as_bytes().len())
+pub unsafe fn lua_pushliteral(L: *mut lua_State, s: &'static CStr) {
+    lua_pushstring(L, s.as_ptr());
 }
 
 #[inline(always)]
@@ -520,7 +519,7 @@ pub const LUA_MASKCOUNT: c_int = 1 << (LUA_HOOKCOUNT as usize);
 pub type lua_Hook = unsafe extern "C-unwind" fn(L: *mut lua_State, ar: *mut lua_Debug);
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua54", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn lua_getstack(L: *mut lua_State, level: c_int, ar: *mut lua_Debug) -> c_int;
     pub fn lua_getinfo(L: *mut lua_State, what: *const c_char, ar: *mut lua_Debug) -> c_int;
     pub fn lua_getlocal(L: *mut lua_State, ar: *const lua_Debug, n: c_int) -> *const c_char;

mlua-sys/src/lua54/lualib.rs

@@ -1,21 +1,21 @@
 //! Contains definitions from `lualib.h`.
 
-use std::os::raw::c_int;
+use std::os::raw::{c_char, c_int};
 
 use super::lua::lua_State;
 
-pub const LUA_COLIBNAME: &str = "coroutine";
-pub const LUA_TABLIBNAME: &str = "table";
-pub const LUA_IOLIBNAME: &str = "io";
-pub const LUA_OSLIBNAME: &str = "os";
-pub const LUA_STRLIBNAME: &str = "string";
-pub const LUA_UTF8LIBNAME: &str = "utf8";
-pub const LUA_MATHLIBNAME: &str = "math";
-pub const LUA_DBLIBNAME: &str = "debug";
-pub const LUA_LOADLIBNAME: &str = "package";
+pub const LUA_COLIBNAME: *const c_char = cstr!("coroutine");
+pub const LUA_TABLIBNAME: *const c_char = cstr!("table");
+pub const LUA_IOLIBNAME: *const c_char = cstr!("io");
+pub const LUA_OSLIBNAME: *const c_char = cstr!("os");
+pub const LUA_STRLIBNAME: *const c_char = cstr!("string");
+pub const LUA_UTF8LIBNAME: *const c_char = cstr!("utf8");
+pub const LUA_MATHLIBNAME: *const c_char = cstr!("math");
+pub const LUA_DBLIBNAME: *const c_char = cstr!("debug");
+pub const LUA_LOADLIBNAME: *const c_char = cstr!("package");
 
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua54", kind = "raw-dylib"))]
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn luaopen_base(L: *mut lua_State) -> c_int;
     pub fn luaopen_coroutine(L: *mut lua_State) -> c_int;
     pub fn luaopen_table(L: *mut lua_State) -> c_int;

mlua-sys/src/luau/compat.rs

@@ -1,4 +1,4 @@
-//! MLua compatibility layer for Roblox Luau.
+//! MLua compatibility layer for Luau.
 //!
 //! Based on github.com/keplerproject/lua-compat-5.3
 
@@ -10,6 +10,8 @@ use super::lauxlib::*;
 use super::lua::*;
 use super::luacode::*;
 
+pub const LUA_RESUMEERROR: c_int = -1;
+
 unsafe fn compat53_reverse(L: *mut lua_State, mut a: c_int, mut b: c_int) {
     while a < b {
         lua_pushvalue(L, a);
@@ -41,7 +43,7 @@ unsafe fn compat53_findfield(L: *mut lua_State, objidx: c_int, level: c_int) ->
             } else if compat53_findfield(L, objidx, level - 1) != 0 {
                 // try recursively
                 lua_remove(L, -2); // remove table (but keep name)
-                lua_pushliteral(L, ".");
+                lua_pushliteral(L, c".");
                 lua_insert(L, -2); // place '.' between the two names
                 lua_concat(L, 3);
                 return 1;
@@ -75,7 +77,7 @@ unsafe fn compat53_pushfuncname(L: *mut lua_State, level: c_int, ar: *mut lua_De
         lua_pushfstring(L, cstr!("function '%s'"), lua_tostring(L, -1));
         lua_remove(L, -2); // remove name
     } else {
-        lua_pushliteral(L, "?");
+        lua_pushliteral(L, c"?");
     }
 }
 
@@ -108,7 +110,7 @@ pub unsafe fn lua_rotate(L: *mut lua_State, mut idx: c_int, mut n: c_int) {
 #[inline(always)]
 pub unsafe fn lua_copy(L: *mut lua_State, fromidx: c_int, toidx: c_int) {
     let abs_to = lua_absindex(L, toidx);
-    luaL_checkstack(L, 1, cstr!("not enough stack slots"));
+    luaL_checkstack(L, 1, cstr!("not enough stack slots available"));
     lua_pushvalue(L, fromidx);
     lua_replace(L, abs_to);
 }
@@ -125,6 +127,11 @@ pub unsafe fn lua_isinteger(L: *mut lua_State, idx: c_int) -> c_int {
     0
 }
 
+#[inline(always)]
+pub unsafe fn lua_pushinteger(L: *mut lua_State, i: lua_Integer) {
+    lua_pushnumber(L, i as lua_Number);
+}
+
 #[inline(always)]
 pub unsafe fn lua_tointeger(L: *mut lua_State, i: c_int) -> lua_Integer {
     lua_tointegerx(L, i, ptr::null_mut())
@@ -176,6 +183,7 @@ pub unsafe fn lua_geti(L: *mut lua_State, mut idx: c_int, n: lua_Integer) -> c_i
 
 #[inline(always)]
 pub unsafe fn lua_rawgeti(L: *mut lua_State, idx: c_int, n: lua_Integer) -> c_int {
+    let n = n.try_into().expect("cannot convert index from lua_Integer");
     lua_rawgeti_(L, idx, n)
 }
 
@@ -190,7 +198,7 @@ pub unsafe fn lua_rawgetp(L: *mut lua_State, idx: c_int, p: *const c_void) -> c_
 pub unsafe fn lua_getuservalue(L: *mut lua_State, mut idx: c_int) -> c_int {
     luaL_checkstack(L, 2, cstr!("not enough stack slots available"));
     idx = lua_absindex(L, idx);
-    lua_pushliteral(L, "__mlua_uservalues");
+    lua_pushliteral(L, c"__mlua_uservalues");
     if lua_rawget(L, LUA_REGISTRYINDEX) != LUA_TTABLE {
         return LUA_TNIL;
     }
@@ -211,13 +219,14 @@ pub unsafe fn lua_seti(L: *mut lua_State, mut idx: c_int, n: lua_Integer) {
 
 #[inline(always)]
 pub unsafe fn lua_rawseti(L: *mut lua_State, idx: c_int, n: lua_Integer) {
+    let n = n.try_into().expect("cannot convert index from lua_Integer");
     lua_rawseti_(L, idx, n)
 }
 
 #[inline(always)]
 pub unsafe fn lua_rawsetp(L: *mut lua_State, idx: c_int, p: *const c_void) {
     let abs_i = lua_absindex(L, idx);
-    luaL_checkstack(L, 1, cstr!("not enough stack slots"));
+    luaL_checkstack(L, 1, cstr!("not enough stack slots available"));
     lua_pushlightuserdata(L, p as *mut c_void);
     lua_insert(L, -2);
     lua_rawset(L, abs_i);
@@ -227,13 +236,13 @@ pub unsafe fn lua_rawsetp(L: *mut lua_State, idx: c_int, p: *const c_void) {
 pub unsafe fn lua_setuservalue(L: *mut lua_State, mut idx: c_int) {
     luaL_checkstack(L, 4, cstr!("not enough stack slots available"));
     idx = lua_absindex(L, idx);
-    lua_pushliteral(L, "__mlua_uservalues");
+    lua_pushliteral(L, c"__mlua_uservalues");
     lua_pushvalue(L, -1);
     if lua_rawget(L, LUA_REGISTRYINDEX) != LUA_TTABLE {
         lua_pop(L, 1);
         lua_createtable(L, 0, 2); // main table
         lua_createtable(L, 0, 1); // metatable
-        lua_pushliteral(L, "k");
+        lua_pushliteral(L, c"k");
         lua_setfield(L, -2, cstr!("__mode"));
         lua_setmetatable(L, -2);
         lua_pushvalue(L, -2);
@@ -284,6 +293,19 @@ pub unsafe fn lua_resume(L: *mut lua_State, from: *mut lua_State, narg: c_int, n
     ret
 }
 
+#[inline(always)]
+pub unsafe fn lua_resumex(L: *mut lua_State, from: *mut lua_State, narg: c_int, nres: *mut c_int) -> c_int {
+    let ret = if narg == LUA_RESUMEERROR {
+        lua_resumeerror(L, from)
+    } else {
+        lua_resume_(L, from, narg)
+    };
+    if (ret == LUA_OK || ret == LUA_YIELD) && !(nres.is_null()) {
+        *nres = lua_gettop(L);
+    }
+    ret
+}
+
 //
 // lauxlib ported functions
 //
@@ -294,12 +316,30 @@ pub unsafe fn luaL_checkstack(L: *mut lua_State, sz: c_int, msg: *const c_char)
         if !msg.is_null() {
             luaL_error(L, cstr!("stack overflow (%s)"), msg);
         } else {
-            lua_pushliteral(L, "stack overflow");
+            lua_pushliteral(L, c"stack overflow");
             lua_error(L);
         }
     }
 }
 
+#[inline(always)]
+pub unsafe fn luaL_checkinteger(L: *mut lua_State, narg: c_int) -> lua_Integer {
+    let mut isnum = 0;
+    let int = lua_tointegerx(L, narg, &mut isnum);
+    if isnum == 0 {
+        luaL_typeerror(L, narg, lua_typename(L, LUA_TNUMBER));
+    }
+    int
+}
+
+pub unsafe fn luaL_optinteger(L: *mut lua_State, narg: c_int, def: lua_Integer) -> lua_Integer {
+    if lua_isnoneornil(L, narg) != 0 {
+        def
+    } else {
+        luaL_checkinteger(L, narg)
+    }
+}
+
 #[inline(always)]
 pub unsafe fn luaL_getmetafield(L: *mut lua_State, obj: c_int, e: *const c_char) -> c_int {
     if luaL_getmetafield_(L, obj, e) != 0 {
@@ -326,12 +366,16 @@ pub unsafe fn luaL_loadbufferenv(
     mut size: usize,
     name: *const c_char,
     mode: *const c_char,
-    env: c_int,
+    mut env: c_int,
 ) -> c_int {
-    extern "C" {
+    unsafe extern "C" {
         fn free(p: *mut c_void);
     }
 
+    unsafe extern "C" fn data_dtor(_: *mut lua_State, data: *mut c_void) {
+        free(*(data as *mut *mut c_char) as *mut c_void);
+    }
+
     let chunk_is_text = size == 0 || (*data as u8) >= b'\t';
     if !mode.is_null() {
         let modeb = CStr::from_ptr(mode).to_bytes();
@@ -344,16 +388,30 @@ pub unsafe fn luaL_loadbufferenv(
         }
     }
 
-    if chunk_is_text {
-        let data = luau_compile_(data, size, ptr::null_mut(), &mut size);
-        let ok = luau_load(L, name, data, size, env) == 0;
-        free(data as *mut c_void);
-        if !ok {
-            return LUA_ERRSYNTAX;
+    let status = if chunk_is_text {
+        if env < 0 {
+            env -= 1;
+        }
+        let data_ud = lua_newuserdatadtor(L, mem::size_of::<*mut c_char>(), data_dtor) as *mut *mut c_char;
+        let data = luau_compile_(data, size, ptr::null_mut(), &mut size);
+        ptr::write(data_ud, data);
+        // By deferring the `free(data)` to the userdata destructor, we ensure that
+        // even if `luau_load` throws an error, the `data` is still released.
+        let status = luau_load(L, name, data, size, env);
+        lua_replace(L, -2); // replace data with the result
+        status
+    } else {
+        luau_load(L, name, data, size, env)
+    };
+
+    if status != 0 {
+        if lua_isstring(L, -1) != 0 && CStr::from_ptr(lua_tostring(L, -1)) == c"not enough memory" {
+            // A case for Luau >= 0.679
+            return LUA_ERRMEM;
         }
-    } else if luau_load(L, name, data, size, env) != 0 {
         return LUA_ERRSYNTAX;
     }
+
     LUA_OK
 }
 
@@ -381,7 +439,7 @@ pub unsafe fn luaL_loadbuffer(
 #[inline(always)]
 pub unsafe fn luaL_len(L: *mut lua_State, idx: c_int) -> lua_Integer {
     let mut isnum = 0;
-    luaL_checkstack(L, 1, cstr!("not enough stack slots"));
+    luaL_checkstack(L, 1, cstr!("not enough stack slots available"));
     lua_len(L, idx);
     let res = lua_tointegerx(L, -1, &mut isnum);
     lua_pop(L, 1);
@@ -404,11 +462,11 @@ pub unsafe fn luaL_traceback(L: *mut lua_State, L1: *mut lua_State, msg: *const
     if !msg.is_null() {
         lua_pushfstring(L, cstr!("%s\n"), msg);
     }
-    lua_pushliteral(L, "stack traceback:");
+    lua_pushliteral(L, c"stack traceback:");
     while lua_getinfo(L1, level, cstr!(""), &mut ar) != 0 {
         if level + 1 == mark {
             // too many levels?
-            lua_pushliteral(L, "\n\t..."); // add a '...'
+            lua_pushliteral(L, c"\n\t..."); // add a '...'
             level = numlevels - COMPAT53_LEVELS2; // and skip to last ones
         } else {
             lua_getinfo(L1, level, cstr!("sln"), &mut ar);
@@ -416,7 +474,7 @@ pub unsafe fn luaL_traceback(L: *mut lua_State, L1: *mut lua_State, msg: *const
             if ar.currentline > 0 {
                 lua_pushfstring(L, cstr!("%d:"), ar.currentline);
             }
-            lua_pushliteral(L, " in ");
+            lua_pushliteral(L, c" in ");
             compat53_pushfuncname(L, level, &mut ar);
             lua_concat(L, lua_gettop(L) - top);
         }
@@ -430,16 +488,16 @@ pub unsafe fn luaL_tolstring(L: *mut lua_State, mut idx: c_int, len: *mut usize)
     if luaL_callmeta(L, idx, cstr!("__tostring")) == 0 {
         match lua_type(L, idx) {
             LUA_TNIL => {
-                lua_pushliteral(L, "nil");
+                lua_pushliteral(L, c"nil");
             }
             LUA_TSTRING | LUA_TNUMBER => {
                 lua_pushvalue(L, idx);
             }
             LUA_TBOOLEAN => {
                 if lua_toboolean(L, idx) == 0 {
-                    lua_pushliteral(L, "false");
+                    lua_pushliteral(L, c"false");
                 } else {
-                    lua_pushliteral(L, "true");
+                    lua_pushliteral(L, c"true");
                 }
             }
             t => {
@@ -463,14 +521,14 @@ pub unsafe fn luaL_tolstring(L: *mut lua_State, mut idx: c_int, len: *mut usize)
 
 #[inline(always)]
 pub unsafe fn luaL_setmetatable(L: *mut lua_State, tname: *const c_char) {
-    luaL_checkstack(L, 1, cstr!("not enough stack slots"));
+    luaL_checkstack(L, 1, cstr!("not enough stack slots available"));
     luaL_getmetatable(L, tname);
     lua_setmetatable(L, -2);
 }
 
 pub unsafe fn luaL_getsubtable(L: *mut lua_State, idx: c_int, fname: *const c_char) -> c_int {
     let abs_i = lua_absindex(L, idx);
-    luaL_checkstack(L, 3, cstr!("not enough stack slots"));
+    luaL_checkstack(L, 3, cstr!("not enough stack slots available"));
     lua_pushstring_(L, fname);
     if lua_gettable(L, abs_i) == LUA_TTABLE {
         return 1;

mlua-sys/src/luau/lauxlib.rs

@@ -3,7 +3,7 @@
 use std::os::raw::{c_char, c_float, c_int, c_void};
 use std::ptr;
 
-use super::lua::{self, lua_CFunction, lua_Integer, lua_Number, lua_State, lua_Unsigned, LUA_REGISTRYINDEX};
+use super::lua::{self, lua_CFunction, lua_Number, lua_State, lua_Unsigned, LUA_REGISTRYINDEX};
 
 #[repr(C)]
 pub struct luaL_Reg {
@@ -11,7 +11,7 @@ pub struct luaL_Reg {
     pub func: lua_CFunction,
 }
 
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn luaL_register(L: *mut lua_State, libname: *const c_char, l: *const luaL_Reg);
     #[link_name = "luaL_getmetafield"]
     pub fn luaL_getmetafield_(L: *mut lua_State, obj: c_int, e: *const c_char) -> c_int;
@@ -33,8 +33,10 @@ extern "C-unwind" {
     pub fn luaL_checkboolean(L: *mut lua_State, narg: c_int) -> c_int;
     pub fn luaL_optboolean(L: *mut lua_State, narg: c_int, def: c_int) -> c_int;
 
-    pub fn luaL_checkinteger(L: *mut lua_State, narg: c_int) -> lua_Integer;
-    pub fn luaL_optinteger(L: *mut lua_State, narg: c_int, def: lua_Integer) -> lua_Integer;
+    #[link_name = "luaL_checkinteger"]
+    pub fn luaL_checkinteger_(L: *mut lua_State, narg: c_int) -> c_int;
+    #[link_name = "luaL_optinteger"]
+    pub fn luaL_optinteger_(L: *mut lua_State, narg: c_int, def: c_int) -> c_int;
     pub fn luaL_checkunsigned(L: *mut lua_State, narg: c_int) -> lua_Unsigned;
     pub fn luaL_optunsigned(L: *mut lua_State, narg: c_int, def: lua_Unsigned) -> lua_Unsigned;
 
@@ -69,10 +71,17 @@ extern "C-unwind" {
 
     pub fn luaL_newstate() -> *mut lua_State;
 
-    // TODO: luaL_findtable
+    pub fn luaL_findtable(
+        L: *mut lua_State,
+        idx: c_int,
+        fname: *const c_char,
+        szhint: c_int,
+    ) -> *const c_char;
 
     pub fn luaL_typename(L: *mut lua_State, idx: c_int) -> *const c_char;
 
+    pub fn luaL_callyieldable(L: *mut lua_State, nargs: c_int, nresults: c_int) -> c_int;
+
     // sandbox libraries and globals
     #[link_name = "luaL_sandbox"]
     pub fn luaL_sandbox_(L: *mut lua_State);
@@ -141,7 +150,7 @@ pub unsafe fn luaL_sandbox(L: *mut lua_State, enabled: c_int) {
     }
 
     // set all builtin metatables to read-only
-    lua_pushliteral(L, "");
+    lua_pushliteral(L, c"");
     if lua_getmetatable(L, -1) != 0 {
         lua_setreadonly(L, -1, enabled);
         lua_pop(L, 2);
@@ -173,7 +182,7 @@ pub struct luaL_Strbuf {
 // For compatibility
 pub type luaL_Buffer = luaL_Strbuf;
 
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn luaL_buffinit(L: *mut lua_State, B: *mut luaL_Strbuf);
     pub fn luaL_buffinitsize(L: *mut lua_State, B: *mut luaL_Strbuf, size: usize) -> *mut c_char;
     pub fn luaL_prepbuffsize(B: *mut luaL_Strbuf, size: usize) -> *mut c_char;

mlua-sys/src/luau/lua.rs

@@ -1,5 +1,6 @@
 //! Contains definitions from `lua.h`.
 
+use std::ffi::CStr;
 use std::marker::{PhantomData, PhantomPinned};
 use std::os::raw::{c_char, c_double, c_float, c_int, c_uint, c_void};
 use std::{mem, ptr};
@@ -11,10 +12,10 @@ pub const LUA_MULTRET: c_int = -1;
 const LUAI_MAXCSTACK: c_int = 1000000;
 
 // Number of valid Lua userdata tags
-const LUA_UTAG_LIMIT: c_int = 128;
+pub const LUA_UTAG_LIMIT: c_int = 128;
 
 // Number of valid Lua lightuserdata tags
-const LUA_LUTAG_LIMIT: c_int = 128;
+pub const LUA_LUTAG_LIMIT: c_int = 128;
 
 //
 // Pseudo-indices
@@ -69,8 +70,11 @@ pub const LUA_MINSTACK: c_int = 20;
 /// A Lua number, usually equivalent to `f64`.
 pub type lua_Number = c_double;
 
-/// A Lua integer, equivalent to `i32`.
-pub type lua_Integer = c_int;
+/// A Lua integer, usually equivalent to `i64`
+#[cfg(target_pointer_width = "32")]
+pub type lua_Integer = i32;
+#[cfg(target_pointer_width = "64")]
+pub type lua_Integer = i64;
 
 /// A Lua unsigned integer, equivalent to `u32`.
 pub type lua_Unsigned = c_uint;
@@ -79,20 +83,19 @@ pub type lua_Unsigned = c_uint;
 pub type lua_CFunction = unsafe extern "C-unwind" fn(L: *mut lua_State) -> c_int;
 pub type lua_Continuation = unsafe extern "C-unwind" fn(L: *mut lua_State, status: c_int) -> c_int;
 
-/// Type for userdata destructor functions.
-pub type lua_Udestructor = unsafe extern "C-unwind" fn(*mut c_void);
-pub type lua_Destructor = unsafe extern "C-unwind" fn(L: *mut lua_State, *mut c_void);
+/// Type for userdata destructor functions (no unwinding).
+pub type lua_Destructor = unsafe extern "C" fn(L: *mut lua_State, *mut c_void);
 
-/// Type for memory-allocation functions.
+/// Type for memory-allocation functions (no unwinding).
 pub type lua_Alloc =
-    unsafe extern "C-unwind" fn(ud: *mut c_void, ptr: *mut c_void, osize: usize, nsize: usize) -> *mut c_void;
+    unsafe extern "C" fn(ud: *mut c_void, ptr: *mut c_void, osize: usize, nsize: usize) -> *mut c_void;
 
 /// Returns Luau release version (eg. `0.xxx`).
 pub const fn luau_version() -> Option<&'static str> {
     option_env!("LUAU_VERSION")
 }
 
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     //
     // State manipulation
     //
@@ -136,7 +139,7 @@ extern "C-unwind" {
 
     pub fn lua_tonumberx(L: *mut lua_State, idx: c_int, isnum: *mut c_int) -> lua_Number;
     #[link_name = "lua_tointegerx"]
-    pub fn lua_tointegerx_(L: *mut lua_State, idx: c_int, isnum: *mut c_int) -> lua_Integer;
+    pub fn lua_tointegerx_(L: *mut lua_State, idx: c_int, isnum: *mut c_int) -> c_int;
     pub fn lua_tounsignedx(L: *mut lua_State, idx: c_int, isnum: *mut c_int) -> lua_Unsigned;
     pub fn lua_tovector(L: *mut lua_State, idx: c_int) -> *const c_float;
     pub fn lua_toboolean(L: *mut lua_State, idx: c_int) -> c_int;
@@ -160,7 +163,8 @@ extern "C-unwind" {
     //
     pub fn lua_pushnil(L: *mut lua_State);
     pub fn lua_pushnumber(L: *mut lua_State, n: lua_Number);
-    pub fn lua_pushinteger(L: *mut lua_State, n: lua_Integer);
+    #[link_name = "lua_pushinteger"]
+    pub fn lua_pushinteger_(L: *mut lua_State, n: c_int);
     pub fn lua_pushunsigned(L: *mut lua_State, n: lua_Unsigned);
     #[cfg(not(feature = "luau-vector4"))]
     pub fn lua_pushvector(L: *mut lua_State, x: c_float, y: c_float, z: c_float);
@@ -185,7 +189,8 @@ extern "C-unwind" {
 
     pub fn lua_pushlightuserdatatagged(L: *mut lua_State, p: *mut c_void, tag: c_int);
     pub fn lua_newuserdatatagged(L: *mut lua_State, sz: usize, tag: c_int) -> *mut c_void;
-    pub fn lua_newuserdatadtor(L: *mut lua_State, sz: usize, dtor: lua_Udestructor) -> *mut c_void;
+    pub fn lua_newuserdatataggedwithmetatable(L: *mut lua_State, sz: usize, tag: c_int) -> *mut c_void;
+    pub fn lua_newuserdatadtor(L: *mut lua_State, sz: usize, dtor: lua_Destructor) -> *mut c_void;
 
     pub fn lua_newbuffer(L: *mut lua_State, sz: usize) -> *mut c_void;
 
@@ -259,14 +264,14 @@ pub const LUA_GCSETGOAL: c_int = 7;
 pub const LUA_GCSETSTEPMUL: c_int = 8;
 pub const LUA_GCSETSTEPSIZE: c_int = 9;
 
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn lua_gc(L: *mut lua_State, what: c_int, data: c_int) -> c_int;
 }
 
 //
 // Memory statistics
 //
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn lua_setmemcat(L: *mut lua_State, category: c_int);
     pub fn lua_totalbytes(L: *mut lua_State, category: c_int) -> usize;
 }
@@ -274,7 +279,7 @@ extern "C-unwind" {
 //
 // Miscellaneous functions
 //
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn lua_error(L: *mut lua_State) -> !;
     pub fn lua_next(L: *mut lua_State, idx: c_int) -> c_int;
     pub fn lua_rawiter(L: *mut lua_State, idx: c_int, iter: c_int) -> c_int;
@@ -284,7 +289,7 @@ extern "C-unwind" {
     pub fn lua_setuserdatatag(L: *mut lua_State, idx: c_int, tag: c_int);
     pub fn lua_setuserdatadtor(L: *mut lua_State, tag: c_int, dtor: Option<lua_Destructor>);
     pub fn lua_getuserdatadtor(L: *mut lua_State, tag: c_int) -> Option<lua_Destructor>;
-    pub fn lua_setuserdatametatable(L: *mut lua_State, tag: c_int, idx: c_int);
+    pub fn lua_setuserdatametatable(L: *mut lua_State, tag: c_int);
     pub fn lua_getuserdatametatable(L: *mut lua_State, tag: c_int);
     pub fn lua_setlightuserdataname(L: *mut lua_State, tag: c_int, name: *const c_char);
     pub fn lua_getlightuserdataname(L: *mut lua_State, tag: c_int) -> *const c_char;
@@ -299,7 +304,7 @@ extern "C-unwind" {
 pub const LUA_NOREF: c_int = -1;
 pub const LUA_REFNIL: c_int = 0;
 
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn lua_ref(L: *mut lua_State, idx: c_int) -> c_int;
     pub fn lua_unref(L: *mut lua_State, r#ref: c_int);
 }
@@ -309,13 +314,13 @@ extern "C-unwind" {
 //
 
 #[inline(always)]
-pub unsafe fn lua_tonumber(L: *mut lua_State, i: c_int) -> lua_Number {
-    lua_tonumberx(L, i, ptr::null_mut())
+pub unsafe fn lua_tonumber(L: *mut lua_State, idx: c_int) -> lua_Number {
+    lua_tonumberx(L, idx, ptr::null_mut())
 }
 
 #[inline(always)]
-pub unsafe fn lua_tointeger_(L: *mut lua_State, i: c_int) -> lua_Integer {
-    lua_tointegerx_(L, i, ptr::null_mut())
+pub unsafe fn lua_tointeger_(L: *mut lua_State, idx: c_int) -> c_int {
+    lua_tointegerx_(L, idx, ptr::null_mut())
 }
 
 #[inline(always)]
@@ -339,12 +344,14 @@ pub unsafe fn lua_newuserdata(L: *mut lua_State, sz: usize) -> *mut c_void {
 }
 
 #[inline(always)]
-pub unsafe fn lua_newuserdata_t<T>(L: *mut lua_State) -> *mut T {
-    unsafe extern "C-unwind" fn destructor<T>(ud: *mut c_void) {
+pub unsafe fn lua_newuserdata_t<T>(L: *mut lua_State, data: T) -> *mut T {
+    unsafe extern "C" fn destructor<T>(_: *mut lua_State, ud: *mut c_void) {
         ptr::drop_in_place(ud as *mut T);
     }
 
-    lua_newuserdatadtor(L, mem::size_of::<T>(), destructor::<T>) as *mut T
+    let ud_ptr = lua_newuserdatadtor(L, const { mem::size_of::<T>() }, destructor::<T>) as *mut T;
+    ptr::write(ud_ptr, data);
+    ud_ptr
 }
 
 // TODO: lua_strlen
@@ -400,10 +407,8 @@ pub unsafe fn lua_isnoneornil(L: *mut lua_State, n: c_int) -> c_int {
 }
 
 #[inline(always)]
-pub unsafe fn lua_pushliteral(L: *mut lua_State, s: &'static str) {
-    use std::ffi::CString;
-    let c_str = CString::new(s).unwrap();
-    lua_pushlstring_(L, c_str.as_ptr(), c_str.as_bytes().len())
+pub unsafe fn lua_pushliteral(L: *mut lua_State, s: &'static CStr) {
+    lua_pushstring_(L, s.as_ptr());
 }
 
 #[inline(always)]
@@ -465,7 +470,7 @@ pub type lua_Coverage = unsafe extern "C-unwind" fn(
     size: usize,
 );
 
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn lua_stackdepth(L: *mut lua_State) -> c_int;
     pub fn lua_getinfo(L: *mut lua_State, level: c_int, what: *const c_char, ar: *mut lua_Debug) -> c_int;
     pub fn lua_getargument(L: *mut lua_State, level: c_int, n: c_int) -> c_int;
@@ -526,13 +531,17 @@ pub struct lua_Callbacks {
     pub debuginterrupt: Option<unsafe extern "C-unwind" fn(L: *mut lua_State, ar: *mut lua_Debug)>,
     /// gets called when protected call results in an error
     pub debugprotectederror: Option<unsafe extern "C-unwind" fn(L: *mut lua_State)>,
+
+    /// gets called when memory is allocated
+    pub onallocate: Option<unsafe extern "C-unwind" fn(L: *mut lua_State, osize: usize, nsize: usize)>,
 }
 
-extern "C" {
+unsafe extern "C" {
     pub fn lua_callbacks(L: *mut lua_State) -> *mut lua_Callbacks;
 }
 
 // Functions from customization lib
-extern "C" {
+unsafe extern "C" {
     pub fn luau_setfflag(name: *const c_char, value: c_int) -> c_int;
+    pub fn lua_getmetatablepointer(L: *mut lua_State, idx: c_int) -> *const c_void;
 }

mlua-sys/src/luau/luacode.rs

@@ -1,5 +1,6 @@
 //! Contains definitions from `luacode.h`.
 
+use std::marker::{PhantomData, PhantomPinned};
 use std::os::raw::{c_char, c_int, c_void};
 use std::{ptr, slice};
 
@@ -15,6 +16,10 @@ pub struct lua_CompileOptions {
     pub vectorType: *const c_char,
     pub mutableGlobals: *const *const c_char,
     pub userdataTypes: *const *const c_char,
+    pub librariesWithKnownMembers: *const *const c_char,
+    pub libraryMemberTypeCallback: Option<lua_LibraryMemberTypeCallback>,
+    pub libraryMemberConstantCallback: Option<lua_LibraryMemberConstantCallback>,
+    pub disabledBuiltins: *const *const c_char,
 }
 
 impl Default for lua_CompileOptions {
@@ -29,11 +34,57 @@ impl Default for lua_CompileOptions {
             vectorType: ptr::null(),
             mutableGlobals: ptr::null(),
             userdataTypes: ptr::null(),
+            librariesWithKnownMembers: ptr::null(),
+            libraryMemberTypeCallback: None,
+            libraryMemberConstantCallback: None,
+            disabledBuiltins: ptr::null(),
         }
     }
 }
 
-extern "C-unwind" {
+#[repr(C)]
+pub struct lua_CompileConstant {
+    _data: [u8; 0],
+    _marker: PhantomData<(*mut u8, PhantomPinned)>,
+}
+
+/// Type table tags
+#[doc(hidden)]
+#[repr(i32)]
+#[non_exhaustive]
+pub enum luau_BytecodeType {
+    Nil = 0,
+    Boolean,
+    Number,
+    String,
+    Table,
+    Function,
+    Thread,
+    UserData,
+    Vector,
+    Buffer,
+
+    Any = 15,
+}
+
+pub type lua_LibraryMemberTypeCallback =
+    unsafe extern "C-unwind" fn(library: *const c_char, member: *const c_char) -> c_int;
+
+pub type lua_LibraryMemberConstantCallback = unsafe extern "C-unwind" fn(
+    library: *const c_char,
+    member: *const c_char,
+    constant: *mut lua_CompileConstant,
+);
+
+unsafe extern "C" {
+    pub fn luau_set_compile_constant_nil(cons: *mut lua_CompileConstant);
+    pub fn luau_set_compile_constant_boolean(cons: *mut lua_CompileConstant, b: c_int);
+    pub fn luau_set_compile_constant_number(cons: *mut lua_CompileConstant, n: f64);
+    pub fn luau_set_compile_constant_vector(cons: *mut lua_CompileConstant, x: f32, y: f32, z: f32, w: f32);
+    pub fn luau_set_compile_constant_string(cons: *mut lua_CompileConstant, s: *const c_char, l: usize);
+}
+
+unsafe extern "C-unwind" {
     #[link_name = "luau_compile"]
     pub fn luau_compile_(
         source: *const c_char,
@@ -43,7 +94,7 @@ extern "C-unwind" {
     ) -> *mut c_char;
 }
 
-extern "C" {
+unsafe extern "C" {
     fn free(p: *mut c_void);
 }
 

mlua-sys/src/luau/luacodegen.rs

@@ -4,7 +4,7 @@ use std::os::raw::c_int;
 
 use super::lua::lua_State;
 
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn luau_codegen_supported() -> c_int;
     pub fn luau_codegen_create(state: *mut lua_State);
     pub fn luau_codegen_compile(state: *mut lua_State, idx: c_int);

mlua-sys/src/luau/lualib.rs

@@ -1,20 +1,21 @@
 //! Contains definitions from `lualib.h`.
 
-use std::os::raw::c_int;
+use std::os::raw::{c_char, c_int};
 
 use super::lua::lua_State;
 
-pub const LUA_COLIBNAME: &str = "coroutine";
-pub const LUA_TABLIBNAME: &str = "table";
-pub const LUA_OSLIBNAME: &str = "os";
-pub const LUA_STRLIBNAME: &str = "string";
-pub const LUA_BITLIBNAME: &str = "bit32";
-pub const LUA_BUFFERLIBNAME: &str = "buffer";
-pub const LUA_UTF8LIBNAME: &str = "utf8";
-pub const LUA_MATHLIBNAME: &str = "math";
-pub const LUA_DBLIBNAME: &str = "debug";
+pub const LUA_COLIBNAME: *const c_char = cstr!("coroutine");
+pub const LUA_TABLIBNAME: *const c_char = cstr!("table");
+pub const LUA_OSLIBNAME: *const c_char = cstr!("os");
+pub const LUA_STRLIBNAME: *const c_char = cstr!("string");
+pub const LUA_BITLIBNAME: *const c_char = cstr!("bit32");
+pub const LUA_BUFFERLIBNAME: *const c_char = cstr!("buffer");
+pub const LUA_UTF8LIBNAME: *const c_char = cstr!("utf8");
+pub const LUA_MATHLIBNAME: *const c_char = cstr!("math");
+pub const LUA_DBLIBNAME: *const c_char = cstr!("debug");
+pub const LUA_VECLIBNAME: *const c_char = cstr!("vector");
 
-extern "C-unwind" {
+unsafe extern "C-unwind" {
     pub fn luaopen_base(L: *mut lua_State) -> c_int;
     pub fn luaopen_coroutine(L: *mut lua_State) -> c_int;
     pub fn luaopen_table(L: *mut lua_State) -> c_int;
@@ -25,6 +26,7 @@ extern "C-unwind" {
     pub fn luaopen_utf8(L: *mut lua_State) -> c_int;
     pub fn luaopen_math(L: *mut lua_State) -> c_int;
     pub fn luaopen_debug(L: *mut lua_State) -> c_int;
+    pub fn luaopen_vector(L: *mut lua_State) -> c_int;
 
     // open all builtin libraries
     pub fn luaL_openlibs(L: *mut lua_State);

mlua-sys/src/luau/luarequire.rs

@@ -0,0 +1,177 @@
+//! Contains definitions from `Require.h`.
+
+use std::os::raw::{c_char, c_int, c_void};
+
+use super::lua::lua_State;
+
+pub const LUA_REGISTERED_MODULES_TABLE: *const c_char = cstr!("_REGISTEREDMODULES");
+
+#[repr(C)]
+pub enum luarequire_NavigateResult {
+    Success,
+    Ambiguous,
+    NotFound,
+}
+
+// Functions returning WriteSuccess are expected to set their size_out argument
+// to the number of bytes written to the buffer. If WriteBufferTooSmall is
+// returned, size_out should be set to the required buffer size.
+#[repr(C)]
+pub enum luarequire_WriteResult {
+    Success,
+    BufferTooSmall,
+    Failure,
+}
+
+#[repr(C)]
+pub struct luarequire_Configuration {
+    // Returns whether requires are permitted from the given chunkname.
+    pub is_require_allowed: unsafe extern "C-unwind" fn(
+        L: *mut lua_State,
+        ctx: *mut c_void,
+        requirer_chunkname: *const c_char,
+    ) -> bool,
+
+    // Resets the internal state to point at the requirer module.
+    pub reset: unsafe extern "C-unwind" fn(
+        L: *mut lua_State,
+        ctx: *mut c_void,
+        requirer_chunkname: *const c_char,
+    ) -> luarequire_NavigateResult,
+
+    // Resets the internal state to point at an aliased module, given its exact path from a configuration
+    // file. This function is only called when an alias's path cannot be resolved relative to its
+    // configuration file.
+    pub jump_to_alias: unsafe extern "C-unwind" fn(
+        L: *mut lua_State,
+        ctx: *mut c_void,
+        path: *const c_char,
+    ) -> luarequire_NavigateResult,
+
+    // Navigates through the context by making mutations to the internal state.
+    pub to_parent:
+        unsafe extern "C-unwind" fn(L: *mut lua_State, ctx: *mut c_void) -> luarequire_NavigateResult,
+    pub to_child: unsafe extern "C-unwind" fn(
+        L: *mut lua_State,
+        ctx: *mut c_void,
+        name: *const c_char,
+    ) -> luarequire_NavigateResult,
+
+    // Returns whether the context is currently pointing at a module.
+    pub is_module_present: unsafe extern "C-unwind" fn(L: *mut lua_State, ctx: *mut c_void) -> bool,
+
+    // Provides a chunkname for the current module. This will be accessible through the debug library. This
+    // function is only called if is_module_present returns true.
+    pub get_chunkname: unsafe extern "C-unwind" fn(
+        L: *mut lua_State,
+        ctx: *mut c_void,
+        buffer: *mut c_char,
+        buffer_size: usize,
+        size_out: *mut usize,
+    ) -> luarequire_WriteResult,
+
+    // Provides a loadname that identifies the current module and is passed to load. This function
+    // is only called if is_module_present returns true.
+    pub get_loadname: unsafe extern "C-unwind" fn(
+        L: *mut lua_State,
+        ctx: *mut c_void,
+        buffer: *mut c_char,
+        buffer_size: usize,
+        size_out: *mut usize,
+    ) -> luarequire_WriteResult,
+
+    // Provides a cache key representing the current module. This function is only called if
+    // is_module_present returns true.
+    pub get_cache_key: unsafe extern "C-unwind" fn(
+        L: *mut lua_State,
+        ctx: *mut c_void,
+        buffer: *mut c_char,
+        buffer_size: usize,
+        size_out: *mut usize,
+    ) -> luarequire_WriteResult,
+
+    // Returns whether a configuration file is present in the current context.
+    // If not, require-by-string will call to_parent until either a configuration file is present or
+    // NAVIGATE_FAILURE is returned (at root).
+    pub is_config_present: unsafe extern "C-unwind" fn(L: *mut lua_State, ctx: *mut c_void) -> bool,
+
+    // Parses the configuration file in the current context for the given alias and returns its
+    // value or WRITE_FAILURE if not found. This function is only called if is_config_present
+    // returns true. If this function pointer is set, get_config must not be set. Opting in to this
+    // function pointer disables parsing configuration files internally and can be used for finer
+    // control over the configuration file parsing process.
+    pub get_alias: Option<
+        unsafe extern "C-unwind" fn(
+            L: *mut lua_State,
+            ctx: *mut c_void,
+            alias: *const c_char,
+            buffer: *mut c_char,
+            buffer_size: usize,
+            size_out: *mut usize,
+        ) -> luarequire_WriteResult,
+    >,
+
+    // Provides the contents of the configuration file in the current context. This function is only called
+    // if is_config_present returns true. If this function pointer is set, get_alias must not be set. Opting
+    // in to this function pointer enables parsing configuration files internally.
+    pub get_config: Option<
+        unsafe extern "C-unwind" fn(
+            L: *mut lua_State,
+            ctx: *mut c_void,
+            buffer: *mut c_char,
+            buffer_size: usize,
+            size_out: *mut usize,
+        ) -> luarequire_WriteResult,
+    >,
+
+    // Executes the module and places the result on the stack. Returns the number of results placed on the
+    // stack.
+    // Returning -1 directs the requiring thread to yield. In this case, this thread should be resumed with
+    // the module result pushed onto its stack.
+    pub load: unsafe extern "C-unwind" fn(
+        L: *mut lua_State,
+        ctx: *mut c_void,
+        path: *const c_char,
+        chunkname: *const c_char,
+        loadname: *const c_char,
+    ) -> c_int,
+}
+
+// Populates function pointers in the given luarequire_Configuration.
+pub type luarequire_Configuration_init = unsafe extern "C-unwind" fn(config: *mut luarequire_Configuration);
+
+unsafe extern "C-unwind" {
+    // Initializes and pushes the require closure onto the stack without registration.
+    pub fn luarequire_pushrequire(
+        L: *mut lua_State,
+        config_init: luarequire_Configuration_init,
+        ctx: *mut c_void,
+    ) -> c_int;
+
+    // Initializes the require library and registers it globally.
+    pub fn luaopen_require(L: *mut lua_State, config_init: luarequire_Configuration_init, ctx: *mut c_void);
+
+    // Initializes and pushes a "proxyrequire" closure onto the stack.
+    //
+    // The closure takes two parameters: the string path to resolve and the chunkname of an existing
+    // module.
+    pub fn luarequire_pushproxyrequire(
+        L: *mut lua_State,
+        config_init: luarequire_Configuration_init,
+        ctx: *mut c_void,
+    ) -> c_int;
+
+    // Registers an aliased require path to a result.
+    //
+    // After registration, the given result will always be immediately returned when the given path is
+    // required.
+    // Expects the path and table to be passed as arguments on the stack.
+    pub fn luarequire_registermodule(L: *mut lua_State) -> c_int;
+
+    // Clears the entry associated with the given cache key from the require cache.
+    // Expects the cache key to be passed as an argument on the stack.
+    pub fn luarequire_clearcacheentry(L: *mut lua_State) -> c_int;
+
+    // Clears all entries from the require cache.
+    pub fn luarequire_clearcache(L: *mut lua_State) -> c_int;
+}

mlua-sys/src/luau/mod.rs

@@ -6,6 +6,7 @@ pub use lua::*;
 pub use luacode::*;
 pub use luacodegen::*;
 pub use lualib::*;
+pub use luarequire::*;
 
 pub mod compat;
 pub mod lauxlib;
@@ -13,3 +14,4 @@ pub mod lua;
 pub mod luacode;
 pub mod luacodegen;
 pub mod lualib;
+pub mod luarequire;

mlua_derive/Cargo.toml

@@ -1,10 +1,10 @@
 [package]
 name = "mlua_derive"
-version = "0.10.0-beta.1"
+version = "0.11.0"
 authors = ["Aleksandr Orlenko <zxteam@pm.me>"]
 edition = "2021"
 description = "Procedural macros for the mlua crate."
-repository = "https://github.com/khvzak/mlua"
+repository = "https://github.com/mlua-rs/mlua"
 keywords = ["lua", "mlua"]
 license = "MIT"
 
@@ -12,13 +12,13 @@ license = "MIT"
 proc-macro = true
 
 [features]
-macros = ["proc-macro-error", "itertools", "regex", "once_cell"]
+macros = ["proc-macro-error2", "itertools", "regex", "once_cell"]
 
 [dependencies]
 quote = "1.0"
 proc-macro2 = { version = "1.0", features = ["span-locations"] }
-proc-macro-error = { version = "1.0", optional = true }
+proc-macro-error2 = { version = "2.0.1", optional = true }
 syn = { version = "2.0", features = ["full"] }
-itertools = { version = "0.13", optional = true }
+itertools = { version = "0.14", optional = true }
 regex = { version = "1.4", optional = true }
 once_cell = { version = "1.0", optional = true }

mlua_derive/src/from_lua.rs

@@ -20,7 +20,7 @@ pub fn from_lua(input: TokenStream) -> TokenStream {
             ::mlua::Value::UserData(ud) => Ok(ud.borrow::<Self>()?.clone()),
             _ => Err(::mlua::Error::FromLuaConversionError {
                 from: value.type_name(),
-                to: #ident_str,
+                to: #ident_str.to_string(),
                 message: None,
             }),
           }

mlua_derive/src/lib.rs

@@ -7,7 +7,7 @@ use syn::{parse_macro_input, ItemFn, LitStr, Result};
 #[cfg(feature = "macros")]
 use {
     crate::chunk::Chunk, proc_macro::TokenTree, proc_macro2::TokenStream as TokenStream2,
-    proc_macro_error::proc_macro_error,
+    proc_macro_error2::proc_macro_error,
 };
 
 #[derive(Default)]
@@ -103,7 +103,7 @@ pub fn chunk(input: TokenStream) -> TokenStream {
 
         struct InnerChunk<F: FnOnce(&Lua) -> Result<Table>>(Cell<Option<F>>);
 
-        impl<F> AsChunk<'static> for InnerChunk<F>
+        impl<F> AsChunk for InnerChunk<F>
         where
             F: FnOnce(&Lua) -> Result<Table>,
         {
@@ -120,7 +120,7 @@ pub fn chunk(input: TokenStream) -> TokenStream {
                 Some(ChunkMode::Text)
             }
 
-            fn source(self) -> IoResult<Cow<'static, [u8]>> {
+            fn source<'a>(&self) -> IoResult<Cow<'a, [u8]>> {
                 Ok(Cow::Borrowed((#source).as_bytes()))
             }
         }
@@ -129,13 +129,13 @@ pub fn chunk(input: TokenStream) -> TokenStream {
             let globals = lua.globals();
             let env = lua.create_table()?;
             let meta = lua.create_table()?;
-            meta.raw_set("__index", globals.clone())?;
-            meta.raw_set("__newindex", globals)?;
+            meta.raw_set("__index", &globals)?;
+            meta.raw_set("__newindex", &globals)?;
 
             // Add captured variables
             #(#caps)*
 
-            env.set_metatable(Some(meta));
+            env.set_metatable(Some(meta))?;
             Ok(env)
         };
 

mlua_derive/src/token.rs

@@ -74,7 +74,7 @@ fn parse_pos(span: &Span) -> Option<(usize, usize)> {
 fn fallback_span_pos(span: &Span) -> (Pos, Pos) {
     let (start, end) = match parse_pos(span) {
         Some(v) => v,
-        None => proc_macro_error::abort_call_site!("Cannot retrieve span information; please use nightly"),
+        None => proc_macro_error2::abort_call_site!("Cannot retrieve span information; please use nightly"),
     };
     (Pos::new(1, start), Pos::new(1, end))
 }

src/buffer.rs

@@ -0,0 +1,92 @@
+#[cfg(feature = "serde")]
+use serde::ser::{Serialize, Serializer};
+
+use crate::state::RawLua;
+use crate::types::ValueRef;
+
+/// A Luau buffer type.
+///
+/// See the buffer [documentation] for more information.
+///
+/// [documentation]: https://luau.org/library#buffer-library
+#[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
+#[derive(Clone, Debug, PartialEq)]
+pub struct Buffer(pub(crate) ValueRef);
+
+#[cfg_attr(not(feature = "luau"), allow(unused))]
+impl Buffer {
+    /// Copies the buffer data into a new `Vec<u8>`.
+    pub fn to_vec(&self) -> Vec<u8> {
+        let lua = self.0.lua.lock();
+        self.as_slice(&lua).to_vec()
+    }
+
+    /// Returns the length of the buffer.
+    pub fn len(&self) -> usize {
+        let lua = self.0.lua.lock();
+        self.as_slice(&lua).len()
+    }
+
+    /// Returns `true` if the buffer is empty.
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+
+    /// Reads given number of bytes from the buffer at the given offset.
+    ///
+    /// Offset is 0-based.
+    #[track_caller]
+    pub fn read_bytes<const N: usize>(&self, offset: usize) -> [u8; N] {
+        let lua = self.0.lua.lock();
+        let data = self.as_slice(&lua);
+        let mut bytes = [0u8; N];
+        bytes.copy_from_slice(&data[offset..offset + N]);
+        bytes
+    }
+
+    /// Writes given bytes to the buffer at the given offset.
+    ///
+    /// Offset is 0-based.
+    #[track_caller]
+    pub fn write_bytes(&self, offset: usize, bytes: &[u8]) {
+        let lua = self.0.lua.lock();
+        let data = unsafe {
+            let (buf, size) = self.as_raw_parts(&lua);
+            std::slice::from_raw_parts_mut(buf, size)
+        };
+        data[offset..offset + bytes.len()].copy_from_slice(bytes);
+    }
+
+    pub(crate) fn as_slice(&self, lua: &RawLua) -> &[u8] {
+        unsafe {
+            let (buf, size) = self.as_raw_parts(lua);
+            std::slice::from_raw_parts(buf, size)
+        }
+    }
+
+    #[cfg(feature = "luau")]
+    unsafe fn as_raw_parts(&self, lua: &RawLua) -> (*mut u8, usize) {
+        let mut size = 0usize;
+        let buf = ffi::lua_tobuffer(lua.ref_thread(), self.0.index, &mut size);
+        mlua_assert!(!buf.is_null(), "invalid Luau buffer");
+        (buf as *mut u8, size)
+    }
+
+    #[cfg(not(feature = "luau"))]
+    unsafe fn as_raw_parts(&self, lua: &RawLua) -> (*mut u8, usize) {
+        unreachable!()
+    }
+}
+
+#[cfg(feature = "serde")]
+impl Serialize for Buffer {
+    fn serialize<S: Serializer>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error> {
+        let lua = self.0.lua.lock();
+        serializer.serialize_bytes(self.as_slice(&lua))
+    }
+}
+
+#[cfg(feature = "luau")]
+impl crate::types::LuaType for Buffer {
+    const TYPE_ID: std::os::raw::c_int = ffi::LUA_TBUFFER;
+}

src/chunk.rs

@@ -2,6 +2,7 @@ use std::borrow::Cow;
 use std::collections::HashMap;
 use std::ffi::CString;
 use std::io::Result as IoResult;
+use std::panic::Location;
 use std::path::{Path, PathBuf};
 use std::string::String as StdString;
 
@@ -9,14 +10,16 @@ use crate::error::{Error, Result};
 use crate::function::Function;
 use crate::state::{Lua, WeakLua};
 use crate::table::Table;
-use crate::value::{FromLuaMulti, IntoLuaMulti};
+use crate::traits::{FromLuaMulti, IntoLua, IntoLuaMulti};
+use crate::value::Value;
 
 /// Trait for types [loadable by Lua] and convertible to a [`Chunk`]
 ///
 /// [loadable by Lua]: https://www.lua.org/manual/5.4/manual.html#3.3.2
-/// [`Chunk`]: crate::Chunk
-pub trait AsChunk<'a> {
+pub trait AsChunk {
     /// Returns optional chunk name
+    ///
+    /// See [`Chunk::set_name`] for possible name prefixes.
     fn name(&self) -> Option<StdString> {
         None
     }
@@ -35,68 +38,101 @@ pub trait AsChunk<'a> {
     }
 
     /// Returns chunk data (can be text or binary)
-    fn source(self) -> IoResult<Cow<'a, [u8]>>;
+    fn source<'a>(&self) -> IoResult<Cow<'a, [u8]>>
+    where
+        Self: 'a;
 }
 
-impl<'a> AsChunk<'a> for &'a str {
-    fn source(self) -> IoResult<Cow<'a, [u8]>> {
-        Ok(Cow::Borrowed(self.as_ref()))
-    }
-}
-
-impl AsChunk<'static> for StdString {
-    fn source(self) -> IoResult<Cow<'static, [u8]>> {
-        Ok(Cow::Owned(self.into_bytes()))
-    }
-}
-
-impl<'a> AsChunk<'a> for &'a StdString {
-    fn source(self) -> IoResult<Cow<'a, [u8]>> {
+impl AsChunk for &str {
+    fn source<'a>(&self) -> IoResult<Cow<'a, [u8]>>
+    where
+        Self: 'a,
+    {
         Ok(Cow::Borrowed(self.as_bytes()))
     }
 }
 
-impl<'a> AsChunk<'a> for &'a [u8] {
-    fn source(self) -> IoResult<Cow<'a, [u8]>> {
+impl AsChunk for StdString {
+    fn source<'a>(&self) -> IoResult<Cow<'a, [u8]>> {
+        Ok(Cow::Owned(self.clone().into_bytes()))
+    }
+}
+
+impl AsChunk for &StdString {
+    fn source<'a>(&self) -> IoResult<Cow<'a, [u8]>>
+    where
+        Self: 'a,
+    {
+        Ok(Cow::Borrowed(self.as_bytes()))
+    }
+}
+
+impl AsChunk for &[u8] {
+    fn source<'a>(&self) -> IoResult<Cow<'a, [u8]>>
+    where
+        Self: 'a,
+    {
         Ok(Cow::Borrowed(self))
     }
 }
 
-impl AsChunk<'static> for Vec<u8> {
-    fn source(self) -> IoResult<Cow<'static, [u8]>> {
-        Ok(Cow::Owned(self))
+impl AsChunk for Vec<u8> {
+    fn source<'a>(&self) -> IoResult<Cow<'a, [u8]>> {
+        Ok(Cow::Owned(self.clone()))
     }
 }
 
-impl<'a> AsChunk<'a> for &'a Vec<u8> {
-    fn source(self) -> IoResult<Cow<'a, [u8]>> {
-        Ok(Cow::Borrowed(self.as_ref()))
+impl AsChunk for &Vec<u8> {
+    fn source<'a>(&self) -> IoResult<Cow<'a, [u8]>>
+    where
+        Self: 'a,
+    {
+        Ok(Cow::Borrowed(self))
     }
 }
 
-impl AsChunk<'static> for &Path {
+impl AsChunk for &Path {
     fn name(&self) -> Option<StdString> {
         Some(format!("@{}", self.display()))
     }
 
-    fn source(self) -> IoResult<Cow<'static, [u8]>> {
+    fn source<'a>(&self) -> IoResult<Cow<'a, [u8]>> {
         std::fs::read(self).map(Cow::Owned)
     }
 }
 
-impl AsChunk<'static> for PathBuf {
+impl AsChunk for PathBuf {
     fn name(&self) -> Option<StdString> {
         Some(format!("@{}", self.display()))
     }
 
-    fn source(self) -> IoResult<Cow<'static, [u8]>> {
+    fn source<'a>(&self) -> IoResult<Cow<'a, [u8]>> {
         std::fs::read(self).map(Cow::Owned)
     }
 }
 
+impl<C: AsChunk + ?Sized> AsChunk for Box<C> {
+    fn name(&self) -> Option<StdString> {
+        (**self).name()
+    }
+
+    fn environment(&self, lua: &Lua) -> Result<Option<Table>> {
+        (**self).environment(lua)
+    }
+
+    fn mode(&self) -> Option<ChunkMode> {
+        (**self).mode()
+    }
+
+    fn source<'a>(&self) -> IoResult<Cow<'a, [u8]>>
+    where
+        Self: 'a,
+    {
+        (**self).source()
+    }
+}
+
 /// Returned from [`Lua::load`] and is used to finalize loading and executing Lua main chunks.
-///
-/// [`Lua::load`]: crate::Lua::load
 #[must_use = "`Chunk`s do nothing unless one of `exec`, `eval`, `call`, or `into_function` are called on them"]
 pub struct Chunk<'a> {
     pub(crate) lua: WeakLua,
@@ -115,6 +151,49 @@ pub enum ChunkMode {
     Binary,
 }
 
+/// Represents a constant value that can be used by Luau compiler.
+#[cfg(any(feature = "luau", doc))]
+#[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
+#[derive(Clone, Debug)]
+pub enum CompileConstant {
+    Nil,
+    Boolean(bool),
+    Number(crate::Number),
+    Vector(crate::Vector),
+    String(StdString),
+}
+
+#[cfg(any(feature = "luau", doc))]
+impl From<bool> for CompileConstant {
+    fn from(b: bool) -> Self {
+        CompileConstant::Boolean(b)
+    }
+}
+
+#[cfg(any(feature = "luau", doc))]
+impl From<crate::Number> for CompileConstant {
+    fn from(n: crate::Number) -> Self {
+        CompileConstant::Number(n)
+    }
+}
+
+#[cfg(any(feature = "luau", doc))]
+impl From<crate::Vector> for CompileConstant {
+    fn from(v: crate::Vector) -> Self {
+        CompileConstant::Vector(v)
+    }
+}
+
+#[cfg(any(feature = "luau", doc))]
+impl From<&str> for CompileConstant {
+    fn from(s: &str) -> Self {
+        CompileConstant::String(s.to_owned())
+    }
+}
+
+#[cfg(any(feature = "luau", doc))]
+type LibraryMemberConstantMap = HashMap<(StdString, StdString), CompileConstant>;
+
 /// Luau compiler
 #[cfg(any(feature = "luau", doc))]
 #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
@@ -124,11 +203,14 @@ pub struct Compiler {
     debug_level: u8,
     type_info_level: u8,
     coverage_level: u8,
-    vector_lib: Option<String>,
-    vector_ctor: Option<String>,
-    vector_type: Option<String>,
-    mutable_globals: Vec<String>,
-    userdata_types: Vec<String>,
+    vector_lib: Option<StdString>,
+    vector_ctor: Option<StdString>,
+    vector_type: Option<StdString>,
+    mutable_globals: Vec<StdString>,
+    userdata_types: Vec<StdString>,
+    libraries_with_known_members: Vec<StdString>,
+    library_constants: Option<LibraryMemberConstantMap>,
+    disabled_builtins: Vec<StdString>,
 }
 
 #[cfg(any(feature = "luau", doc))]
@@ -153,6 +235,9 @@ impl Compiler {
             vector_type: None,
             mutable_globals: Vec::new(),
             userdata_types: Vec::new(),
+            libraries_with_known_members: Vec::new(),
+            library_constants: None,
+            disabled_builtins: Vec::new(),
         }
     }
 
@@ -185,6 +270,7 @@ impl Compiler {
     /// Possible values:
     /// * 0 - generate for native modules (default)
     /// * 1 - generate for all modules
+    #[must_use]
     pub const fn set_type_info_level(mut self, level: u8) -> Self {
         self.type_info_level = level;
         self
@@ -202,48 +288,113 @@ impl Compiler {
         self
     }
 
+    /// Sets alternative global builtin to construct vectors, in addition to default builtin
+    /// `vector.create`.
+    ///
+    /// To set the library and method name, use the `lib.ctor` format.
     #[doc(hidden)]
     #[must_use]
-    pub fn set_vector_lib(mut self, lib: impl Into<String>) -> Self {
-        self.vector_lib = Some(lib.into());
+    pub fn set_vector_ctor(mut self, ctor: impl Into<StdString>) -> Self {
+        let ctor = ctor.into();
+        let lib_ctor = ctor.split_once('.');
+        self.vector_lib = lib_ctor.as_ref().map(|&(lib, _)| lib.to_owned());
+        self.vector_ctor = (lib_ctor.as_ref())
+            .map(|&(_, ctor)| ctor.to_owned())
+            .or(Some(ctor));
         self
     }
 
+    /// Sets alternative vector type name for type tables, in addition to default type `vector`.
     #[doc(hidden)]
     #[must_use]
-    pub fn set_vector_ctor(mut self, ctor: impl Into<String>) -> Self {
-        self.vector_ctor = Some(ctor.into());
-        self
-    }
-
-    #[doc(hidden)]
-    #[must_use]
-    pub fn set_vector_type(mut self, r#type: impl Into<String>) -> Self {
+    pub fn set_vector_type(mut self, r#type: impl Into<StdString>) -> Self {
         self.vector_type = Some(r#type.into());
         self
     }
 
+    /// Adds a mutable global.
+    ///
+    /// It disables the import optimization for fields accessed through it.
+    #[must_use]
+    pub fn add_mutable_global(mut self, global: impl Into<StdString>) -> Self {
+        self.mutable_globals.push(global.into());
+        self
+    }
+
     /// Sets a list of globals that are mutable.
     ///
     /// It disables the import optimization for fields accessed through these.
     #[must_use]
-    pub fn set_mutable_globals(mut self, globals: Vec<String>) -> Self {
-        self.mutable_globals = globals;
+    pub fn set_mutable_globals<S: Into<StdString>>(mut self, globals: impl IntoIterator<Item = S>) -> Self {
+        self.mutable_globals = globals.into_iter().map(|s| s.into()).collect();
+        self
+    }
+
+    /// Adds a userdata type to the list that will be included in the type information.
+    #[must_use]
+    pub fn add_userdata_type(mut self, r#type: impl Into<StdString>) -> Self {
+        self.userdata_types.push(r#type.into());
         self
     }
 
     /// Sets a list of userdata types that will be included in the type information.
     #[must_use]
-    pub fn set_userdata_types(mut self, types: Vec<String>) -> Self {
-        self.userdata_types = types;
+    pub fn set_userdata_types<S: Into<StdString>>(mut self, types: impl IntoIterator<Item = S>) -> Self {
+        self.userdata_types = types.into_iter().map(|s| s.into()).collect();
+        self
+    }
+
+    /// Adds a constant for a known library member.
+    ///
+    /// The constants are used by the compiler to optimize the generated bytecode.
+    /// Optimization level must be at least 2 for this to have any effect.
+    ///
+    /// The `name` is a string in the format `lib.member`, where `lib` is the library name
+    /// and `member` is the member (constant) name.
+    #[must_use]
+    pub fn add_library_constant(
+        mut self,
+        name: impl AsRef<str>,
+        r#const: impl Into<CompileConstant>,
+    ) -> Self {
+        let Some((lib, member)) = name.as_ref().split_once('.') else {
+            return self;
+        };
+        let (lib, member) = (lib.to_owned(), member.to_owned());
+
+        if !self.libraries_with_known_members.contains(&lib) {
+            self.libraries_with_known_members.push(lib.clone());
+        }
+        self.library_constants
+            .get_or_insert_with(HashMap::new)
+            .insert((lib, member), r#const.into());
+        self
+    }
+
+    /// Adds a builtin that should be disabled.
+    #[must_use]
+    pub fn add_disabled_builtin(mut self, builtin: impl Into<StdString>) -> Self {
+        self.disabled_builtins.push(builtin.into());
+        self
+    }
+
+    /// Sets a list of builtins that should be disabled.
+    #[must_use]
+    pub fn set_disabled_builtins<S: Into<StdString>>(
+        mut self,
+        builtins: impl IntoIterator<Item = S>,
+    ) -> Self {
+        self.disabled_builtins = builtins.into_iter().map(|s| s.into()).collect();
         self
     }
 
     /// Compiles the `source` into bytecode.
     ///
-    /// Returns `Error::SyntaxError` if the source code is invalid.
+    /// Returns [`Error::SyntaxError`] if the source code is invalid.
     pub fn compile(&self, source: impl AsRef<[u8]>) -> Result<Vec<u8>> {
-        use std::os::raw::c_int;
+        use std::cell::RefCell;
+        use std::ffi::CStr;
+        use std::os::raw::{c_char, c_int};
         use std::ptr;
 
         let vector_lib = self.vector_lib.clone();
@@ -275,6 +426,44 @@ impl Compiler {
 
         vec2cstring_ptr!(mutable_globals, mutable_globals_ptr);
         vec2cstring_ptr!(userdata_types, userdata_types_ptr);
+        vec2cstring_ptr!(libraries_with_known_members, libraries_with_known_members_ptr);
+        vec2cstring_ptr!(disabled_builtins, disabled_builtins_ptr);
+
+        thread_local! {
+            static LIBRARY_MEMBER_CONSTANT_MAP: RefCell<LibraryMemberConstantMap> = Default::default();
+        }
+
+        #[cfg(feature = "luau")]
+        unsafe extern "C-unwind" fn library_member_constant_callback(
+            library: *const c_char,
+            member: *const c_char,
+            constant: *mut ffi::lua_CompileConstant,
+        ) {
+            let library = CStr::from_ptr(library).to_string_lossy();
+            let member = CStr::from_ptr(member).to_string_lossy();
+            LIBRARY_MEMBER_CONSTANT_MAP.with_borrow(|map| {
+                if let Some(cons) = map.get(&(library.to_string(), member.to_string())) {
+                    match cons {
+                        CompileConstant::Nil => ffi::luau_set_compile_constant_nil(constant),
+                        CompileConstant::Boolean(b) => {
+                            ffi::luau_set_compile_constant_boolean(constant, *b as c_int)
+                        }
+                        CompileConstant::Number(n) => ffi::luau_set_compile_constant_number(constant, *n),
+                        CompileConstant::Vector(v) => {
+                            #[cfg(not(feature = "luau-vector4"))]
+                            ffi::luau_set_compile_constant_vector(constant, v.x(), v.y(), v.z(), 0.0);
+                            #[cfg(feature = "luau-vector4")]
+                            ffi::luau_set_compile_constant_vector(constant, v.x(), v.y(), v.z(), v.w());
+                        }
+                        CompileConstant::String(s) => ffi::luau_set_compile_constant_string(
+                            constant,
+                            s.as_ptr() as *const c_char,
+                            s.len(),
+                        ),
+                    }
+                }
+            })
+        }
 
         let bytecode = unsafe {
             let mut options = ffi::lua_CompileOptions::default();
@@ -287,13 +476,21 @@ impl Compiler {
             options.vectorType = vector_type.map_or(ptr::null(), |s| s.as_ptr());
             options.mutableGlobals = mutable_globals_ptr;
             options.userdataTypes = userdata_types_ptr;
+            options.librariesWithKnownMembers = libraries_with_known_members_ptr;
+            if let Some(map) = self.library_constants.as_ref() {
+                if !self.libraries_with_known_members.is_empty() {
+                    LIBRARY_MEMBER_CONSTANT_MAP.with_borrow_mut(|gmap| *gmap = map.clone());
+                    options.libraryMemberConstantCallback = Some(library_member_constant_callback);
+                }
+            }
+            options.disabledBuiltins = disabled_builtins_ptr;
             ffi::luau_compile(source.as_ref(), options)
         };
 
         if bytecode.first() == Some(&0) {
             // The rest of the bytecode is the error message starting with `:`
             // See https://github.com/luau-lang/luau/blob/0.640/Compiler/src/Compiler.cpp#L4336
-            let message = String::from_utf8_lossy(&bytecode[2..]).to_string();
+            let message = StdString::from_utf8_lossy(&bytecode[2..]).into_owned();
             return Err(Error::SyntaxError {
                 incomplete_input: message.ends_with("<eof>"),
                 message,
@@ -304,13 +501,28 @@ impl Compiler {
     }
 }
 
-impl<'a> Chunk<'a> {
+impl Chunk<'_> {
+    /// Returns the name of this chunk.
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
     /// Sets the name of this chunk, which results in more informative error traces.
-    pub fn set_name(mut self, name: impl Into<String>) -> Self {
+    ///
+    /// Possible name prefixes:
+    /// - `@` - file path (when truncation is needed, the end of the file path is kept, as this is
+    ///   more useful for identifying the file)
+    /// - `=` - custom chunk name (when truncation is needed, the beginning of the name is kept)
+    pub fn set_name(mut self, name: impl Into<StdString>) -> Self {
         self.name = name.into();
         self
     }
 
+    /// Returns the environment of this chunk.
+    pub fn environment(&self) -> Option<&Table> {
+        self.env.as_ref().ok()?.as_ref()
+    }
+
     /// Sets the environment of the loaded chunk to the given value.
     ///
     /// In Lua >=5.2 main chunks always have exactly one upvalue, and this upvalue is used as the
@@ -327,6 +539,11 @@ impl<'a> Chunk<'a> {
         self
     }
 
+    /// Returns the mode (auto-detected by default) of this chunk.
+    pub fn mode(&self) -> ChunkMode {
+        self.detect_mode()
+    }
+
     /// Sets whether the chunk is text or binary (autodetected by default).
     ///
     /// Be aware, Lua does not check the consistency of the code inside binary chunks.
@@ -339,8 +556,6 @@ impl<'a> Chunk<'a> {
     /// Sets or overwrites a Luau compiler used for this chunk.
     ///
     /// See [`Compiler`] for details and possible options.
-    ///
-    /// Requires `feature = "luau"`
     #[cfg(any(feature = "luau", doc))]
     #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
     pub fn set_compiler(mut self, compiler: Compiler) -> Self {
@@ -359,9 +574,7 @@ impl<'a> Chunk<'a> {
     ///
     /// See [`exec`] for more details.
     ///
-    /// Requires `feature = "async"`
-    ///
-    /// [`exec`]: #method.exec
+    /// [`exec`]: Chunk::exec
     #[cfg(feature = "async")]
     #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
     pub async fn exec_async(self) -> Result<()> {
@@ -391,9 +604,7 @@ impl<'a> Chunk<'a> {
     ///
     /// See [`eval`] for more details.
     ///
-    /// Requires `feature = "async"`
-    ///
-    /// [`eval`]: #method.eval
+    /// [`eval`]: Chunk::eval
     #[cfg(feature = "async")]
     #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
     pub async fn eval_async<R>(self) -> Result<R>
@@ -420,9 +631,7 @@ impl<'a> Chunk<'a> {
     ///
     /// See [`call`] for more details.
     ///
-    /// Requires `feature = "async"`
-    ///
-    /// [`call`]: #method.call
+    /// [`call`]: Chunk::call
     #[cfg(feature = "async")]
     #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
     pub async fn call_async<R>(self, args: impl IntoLuaMulti) -> Result<R>
@@ -432,7 +641,7 @@ impl<'a> Chunk<'a> {
         self.into_function()?.call_async(args).await
     }
 
-    /// Load this chunk into a regular `Function`.
+    /// Load this chunk into a regular [`Function`].
     ///
     /// This simply compiles the chunk without actually executing it.
     #[cfg_attr(not(feature = "luau"), allow(unused_mut))]
@@ -481,7 +690,7 @@ impl<'a> Chunk<'a> {
         if let Ok(ref source) = self.source {
             if self.detect_mode() == ChunkMode::Text {
                 let lua = self.lua.lock();
-                if let Some(cache) = lua.app_data_ref::<ChunksCache>() {
+                if let Some(cache) = lua.priv_app_data_ref::<ChunksCache>() {
                     if let Some(data) = cache.0.get(source.as_ref()) {
                         self.source = Ok(Cow::Owned(data.clone()));
                         self.mode = Some(ChunkMode::Binary);
@@ -498,12 +707,12 @@ impl<'a> Chunk<'a> {
             if let Ok(ref binary_source) = self.source {
                 if self.detect_mode() == ChunkMode::Binary {
                     let lua = self.lua.lock();
-                    if let Some(mut cache) = lua.app_data_mut::<ChunksCache>() {
-                        cache.0.insert(text_source, binary_source.as_ref().to_vec());
+                    if let Some(mut cache) = lua.priv_app_data_mut::<ChunksCache>() {
+                        cache.0.insert(text_source, binary_source.to_vec());
                     } else {
                         let mut cache = ChunksCache(HashMap::new());
-                        cache.0.insert(text_source, binary_source.as_ref().to_vec());
-                        let _ = lua.try_set_app_data(cache);
+                        cache.0.insert(text_source, binary_source.to_vec());
+                        lua.set_priv_app_data(cache);
                     };
                 }
             }
@@ -536,24 +745,23 @@ impl<'a> Chunk<'a> {
     }
 
     fn detect_mode(&self) -> ChunkMode {
-        match (self.mode, &self.source) {
-            (Some(mode), _) => mode,
-            (None, Ok(source)) => {
-                #[cfg(not(feature = "luau"))]
-                if source.starts_with(ffi::LUA_SIGNATURE) {
-                    return ChunkMode::Binary;
-                }
-                #[cfg(feature = "luau")]
-                if *source.first().unwrap_or(&u8::MAX) < b'\n' {
-                    return ChunkMode::Binary;
-                }
-                ChunkMode::Text
-            }
-            (None, Err(_)) => ChunkMode::Text, // any value is fine
+        if let Some(mode) = self.mode {
+            return mode;
         }
+        if let Ok(source) = &self.source {
+            #[cfg(not(feature = "luau"))]
+            if source.starts_with(ffi::LUA_SIGNATURE) {
+                return ChunkMode::Binary;
+            }
+            #[cfg(feature = "luau")]
+            if *source.first().unwrap_or(&u8::MAX) < b'\n' {
+                return ChunkMode::Binary;
+            }
+        }
+        ChunkMode::Text
     }
 
-    fn convert_name(name: String) -> Result<CString> {
+    fn convert_name(name: StdString) -> Result<CString> {
         CString::new(name).map_err(|err| Error::runtime(format!("invalid name: {err}")))
     }
 
@@ -564,3 +772,31 @@ impl<'a> Chunk<'a> {
         buf
     }
 }
+
+struct WrappedChunk<T: AsChunk> {
+    chunk: T,
+    caller: &'static Location<'static>,
+}
+
+impl Chunk<'_> {
+    /// Wraps a chunk of Lua code, returning an opaque type that implements [`IntoLua`] trait.
+    ///
+    /// The resulted `IntoLua` implementation will convert the chunk into a Lua function without
+    /// executing it.
+    #[doc(hidden)]
+    #[track_caller]
+    pub fn wrap(chunk: impl AsChunk) -> impl IntoLua {
+        WrappedChunk {
+            chunk,
+            caller: Location::caller(),
+        }
+    }
+}
+
+impl<T: AsChunk> IntoLua for WrappedChunk<T> {
+    fn into_lua(self, lua: &Lua) -> Result<Value> {
+        lua.load_with_location(self.chunk, self.caller)
+            .into_function()
+            .map(Value::Function)
+    }
+}

src/conversion.rs

@@ -1,23 +1,25 @@
 use std::borrow::Cow;
 use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet};
-use std::ffi::{CStr, CString};
+use std::ffi::{CStr, CString, OsStr, OsString};
 use std::hash::{BuildHasher, Hash};
 use std::os::raw::c_int;
+use std::path::{Path, PathBuf};
 use std::string::String as StdString;
-use std::{slice, str};
+use std::{mem, slice, str};
 
-use bstr::{BStr, BString};
+use bstr::{BStr, BString, ByteSlice, ByteVec};
 use num_traits::cast;
 
 use crate::error::{Error, Result};
 use crate::function::Function;
 use crate::state::{Lua, RawLua};
-use crate::string::String;
+use crate::string::{BorrowedBytes, BorrowedStr, String};
 use crate::table::Table;
 use crate::thread::Thread;
-use crate::types::{LightUserData, MaybeSend, RegistryKey};
+use crate::traits::{FromLua, IntoLua, ShortTypeName as _};
+use crate::types::{Either, LightUserData, MaybeSend, RegistryKey};
 use crate::userdata::{AnyUserData, UserData};
-use crate::value::{FromLua, IntoLua, Nil, Value};
+use crate::value::{Nil, Value};
 
 impl IntoLua for Value {
     #[inline]
@@ -72,7 +74,7 @@ impl FromLua for String {
         lua.coerce_string(value)?
             .ok_or_else(|| Error::FromLuaConversionError {
                 from: ty,
-                to: "string",
+                to: "string".to_string(),
                 message: Some("expected string or number".to_string()),
             })
     }
@@ -89,6 +91,94 @@ impl FromLua for String {
     }
 }
 
+impl IntoLua for BorrowedStr<'_> {
+    #[inline]
+    fn into_lua(self, _: &Lua) -> Result<Value> {
+        Ok(Value::String(self.borrow.into_owned()))
+    }
+
+    #[inline]
+    unsafe fn push_into_stack(self, lua: &RawLua) -> Result<()> {
+        lua.push_ref(&self.borrow.0);
+        Ok(())
+    }
+}
+
+impl IntoLua for &BorrowedStr<'_> {
+    #[inline]
+    fn into_lua(self, _: &Lua) -> Result<Value> {
+        Ok(Value::String(self.borrow.clone().into_owned()))
+    }
+
+    #[inline]
+    unsafe fn push_into_stack(self, lua: &RawLua) -> Result<()> {
+        lua.push_ref(&self.borrow.0);
+        Ok(())
+    }
+}
+
+impl FromLua for BorrowedStr<'_> {
+    fn from_lua(value: Value, lua: &Lua) -> Result<Self> {
+        let s = String::from_lua(value, lua)?;
+        let BorrowedStr { buf, _lua, .. } = BorrowedStr::try_from(&s)?;
+        let buf = unsafe { mem::transmute::<&str, &'static str>(buf) };
+        let borrow = Cow::Owned(s);
+        Ok(Self { buf, borrow, _lua })
+    }
+
+    unsafe fn from_stack(idx: c_int, lua: &RawLua) -> Result<Self> {
+        let s = String::from_stack(idx, lua)?;
+        let BorrowedStr { buf, _lua, .. } = BorrowedStr::try_from(&s)?;
+        let buf = unsafe { mem::transmute::<&str, &'static str>(buf) };
+        let borrow = Cow::Owned(s);
+        Ok(Self { buf, borrow, _lua })
+    }
+}
+
+impl IntoLua for BorrowedBytes<'_> {
+    #[inline]
+    fn into_lua(self, _: &Lua) -> Result<Value> {
+        Ok(Value::String(self.borrow.into_owned()))
+    }
+
+    #[inline]
+    unsafe fn push_into_stack(self, lua: &RawLua) -> Result<()> {
+        lua.push_ref(&self.borrow.0);
+        Ok(())
+    }
+}
+
+impl IntoLua for &BorrowedBytes<'_> {
+    #[inline]
+    fn into_lua(self, _: &Lua) -> Result<Value> {
+        Ok(Value::String(self.borrow.clone().into_owned()))
+    }
+
+    #[inline]
+    unsafe fn push_into_stack(self, lua: &RawLua) -> Result<()> {
+        lua.push_ref(&self.borrow.0);
+        Ok(())
+    }
+}
+
+impl FromLua for BorrowedBytes<'_> {
+    fn from_lua(value: Value, lua: &Lua) -> Result<Self> {
+        let s = String::from_lua(value, lua)?;
+        let BorrowedBytes { buf, _lua, .. } = BorrowedBytes::from(&s);
+        let buf = unsafe { mem::transmute::<&[u8], &'static [u8]>(buf) };
+        let borrow = Cow::Owned(s);
+        Ok(Self { buf, borrow, _lua })
+    }
+
+    unsafe fn from_stack(idx: c_int, lua: &RawLua) -> Result<Self> {
+        let s = String::from_stack(idx, lua)?;
+        let BorrowedBytes { buf, _lua, .. } = BorrowedBytes::from(&s);
+        let buf = unsafe { mem::transmute::<&[u8], &'static [u8]>(buf) };
+        let borrow = Cow::Owned(s);
+        Ok(Self { buf, borrow, _lua })
+    }
+}
+
 impl IntoLua for Table {
     #[inline]
     fn into_lua(self, _: &Lua) -> Result<Value> {
@@ -116,7 +206,7 @@ impl FromLua for Table {
             Value::Table(table) => Ok(table),
             _ => Err(Error::FromLuaConversionError {
                 from: value.type_name(),
-                to: "table",
+                to: "table".to_string(),
                 message: None,
             }),
         }
@@ -150,7 +240,7 @@ impl FromLua for Function {
             Value::Function(table) => Ok(table),
             _ => Err(Error::FromLuaConversionError {
                 from: value.type_name(),
-                to: "function",
+                to: "function".to_string(),
                 message: None,
             }),
         }
@@ -184,7 +274,7 @@ impl FromLua for Thread {
             Value::Thread(t) => Ok(t),
             _ => Err(Error::FromLuaConversionError {
                 from: value.type_name(),
-                to: "thread",
+                to: "thread".to_string(),
                 message: None,
             }),
         }
@@ -218,7 +308,7 @@ impl FromLua for AnyUserData {
             Value::UserData(ud) => Ok(ud),
             _ => Err(Error::FromLuaConversionError {
                 from: value.type_name(),
-                to: "userdata",
+                to: "userdata".to_string(),
                 message: None,
             }),
         }
@@ -241,18 +331,22 @@ impl IntoLua for Error {
 
 impl FromLua for Error {
     #[inline]
-    fn from_lua(value: Value, lua: &Lua) -> Result<Error> {
+    fn from_lua(value: Value, _: &Lua) -> Result<Error> {
         match value {
             Value::Error(err) => Ok(*err),
-            val => Ok(Error::runtime(
-                lua.coerce_string(val)?
-                    .and_then(|s| Some(s.to_str().ok()?.to_owned()))
-                    .unwrap_or_else(|| "<unprintable error>".to_owned()),
-            )),
+            val => Ok(Error::runtime(val.to_string()?)),
         }
     }
 }
 
+#[cfg(feature = "anyhow")]
+impl IntoLua for anyhow::Error {
+    #[inline]
+    fn into_lua(self, _: &Lua) -> Result<Value> {
+        Ok(Value::Error(Box::new(Error::from(self))))
+    }
+}
+
 impl IntoLua for RegistryKey {
     #[inline]
     fn into_lua(self, lua: &Lua) -> Result<Value> {
@@ -336,7 +430,7 @@ impl FromLua for LightUserData {
             Value::LightUserData(ud) => Ok(ud),
             _ => Err(Error::FromLuaConversionError {
                 from: value.type_name(),
-                to: "light userdata",
+                to: "lightuserdata".to_string(),
                 message: None,
             }),
         }
@@ -344,7 +438,7 @@ impl FromLua for LightUserData {
 }
 
 #[cfg(feature = "luau")]
-impl IntoLua for crate::types::Vector {
+impl IntoLua for crate::Vector {
     #[inline]
     fn into_lua(self, _: &Lua) -> Result<Value> {
         Ok(Value::Vector(self))
@@ -352,14 +446,51 @@ impl IntoLua for crate::types::Vector {
 }
 
 #[cfg(feature = "luau")]
-impl FromLua for crate::types::Vector {
+impl FromLua for crate::Vector {
     #[inline]
     fn from_lua(value: Value, _: &Lua) -> Result<Self> {
         match value {
             Value::Vector(v) => Ok(v),
             _ => Err(Error::FromLuaConversionError {
                 from: value.type_name(),
-                to: "vector",
+                to: "vector".to_string(),
+                message: None,
+            }),
+        }
+    }
+}
+
+#[cfg(feature = "luau")]
+impl IntoLua for crate::Buffer {
+    #[inline]
+    fn into_lua(self, _: &Lua) -> Result<Value> {
+        Ok(Value::Buffer(self))
+    }
+}
+
+#[cfg(feature = "luau")]
+impl IntoLua for &crate::Buffer {
+    #[inline]
+    fn into_lua(self, _: &Lua) -> Result<Value> {
+        Ok(Value::Buffer(self.clone()))
+    }
+
+    #[inline]
+    unsafe fn push_into_stack(self, lua: &RawLua) -> Result<()> {
+        lua.push_ref(&self.0);
+        Ok(())
+    }
+}
+
+#[cfg(feature = "luau")]
+impl FromLua for crate::Buffer {
+    #[inline]
+    fn from_lua(value: Value, _: &Lua) -> Result<Self> {
+        match value {
+            Value::Buffer(buf) => Ok(buf),
+            _ => Err(Error::FromLuaConversionError {
+                from: value.type_name(),
+                to: "buffer".to_string(),
                 message: None,
             }),
         }
@@ -386,7 +517,7 @@ impl FromLua for StdString {
             .coerce_string(value)?
             .ok_or_else(|| Error::FromLuaConversionError {
                 from: ty,
-                to: "String",
+                to: Self::type_name(),
                 message: Some("expected string or number".to_string()),
             })?
             .to_str()?
@@ -405,7 +536,7 @@ impl FromLua for StdString {
                 .map(|s| s.to_owned())
                 .map_err(|e| Error::FromLuaConversionError {
                     from: "string",
-                    to: "String",
+                    to: Self::type_name(),
                     message: Some(e.to_string()),
                 });
         }
@@ -448,7 +579,7 @@ impl FromLua for Box<str> {
             .coerce_string(value)?
             .ok_or_else(|| Error::FromLuaConversionError {
                 from: ty,
-                to: "Box<str>",
+                to: Self::type_name(),
                 message: Some("expected string or number".to_string()),
             })?
             .to_str()?
@@ -472,7 +603,7 @@ impl FromLua for CString {
             .coerce_string(value)?
             .ok_or_else(|| Error::FromLuaConversionError {
                 from: ty,
-                to: "CString",
+                to: Self::type_name(),
                 message: Some("expected string or number".to_string()),
             })?;
 
@@ -480,7 +611,7 @@ impl FromLua for CString {
             Ok(s) => Ok(s.into()),
             Err(_) => Err(Error::FromLuaConversionError {
                 from: ty,
-                to: "CString",
+                to: Self::type_name(),
                 message: Some("invalid C-style string".to_string()),
             }),
         }
@@ -514,18 +645,12 @@ impl FromLua for BString {
         match value {
             Value::String(s) => Ok((*s.as_bytes()).into()),
             #[cfg(feature = "luau")]
-            Value::UserData(ud) if ud.1 == crate::types::SubtypeId::Buffer => unsafe {
-                let lua = ud.0.lua.lock();
-                let mut size = 0usize;
-                let buf = ffi::lua_tobuffer(lua.ref_thread(), ud.0.index, &mut size);
-                mlua_assert!(!buf.is_null(), "invalid Luau buffer");
-                Ok(slice::from_raw_parts(buf as *const u8, size).into())
-            },
+            Value::Buffer(buf) => Ok(buf.to_vec().into()),
             _ => Ok((*lua
                 .coerce_string(value)?
                 .ok_or_else(|| Error::FromLuaConversionError {
                     from: ty,
-                    to: "BString",
+                    to: Self::type_name(),
                     message: Some("expected string or number".to_string()),
                 })?
                 .as_bytes())
@@ -563,6 +688,106 @@ impl IntoLua for &BStr {
     }
 }
 
+impl IntoLua for OsString {
+    #[inline]
+    fn into_lua(self, lua: &Lua) -> Result<Value> {
+        self.as_os_str().into_lua(lua)
+    }
+}
+
+impl FromLua for OsString {
+    #[inline]
+    fn from_lua(value: Value, lua: &Lua) -> Result<Self> {
+        let ty = value.type_name();
+        let bs = BString::from_lua(value, lua)?;
+        Vec::from(bs)
+            .into_os_string()
+            .map_err(|err| Error::FromLuaConversionError {
+                from: ty,
+                to: "OsString".into(),
+                message: Some(err.to_string()),
+            })
+    }
+}
+
+impl IntoLua for &OsStr {
+    #[inline]
+    fn into_lua(self, lua: &Lua) -> Result<Value> {
+        let s = <[u8]>::from_os_str(self).ok_or_else(|| Error::ToLuaConversionError {
+            from: "OsStr".into(),
+            to: "string",
+            message: Some("invalid utf-8 encoding".into()),
+        })?;
+        Ok(Value::String(lua.create_string(s)?))
+    }
+}
+
+impl IntoLua for PathBuf {
+    #[inline]
+    fn into_lua(self, lua: &Lua) -> Result<Value> {
+        self.as_os_str().into_lua(lua)
+    }
+}
+
+impl FromLua for PathBuf {
+    #[inline]
+    fn from_lua(value: Value, lua: &Lua) -> Result<Self> {
+        OsString::from_lua(value, lua).map(PathBuf::from)
+    }
+}
+
+impl IntoLua for &Path {
+    #[inline]
+    fn into_lua(self, lua: &Lua) -> Result<Value> {
+        self.as_os_str().into_lua(lua)
+    }
+}
+
+impl IntoLua for char {
+    #[inline]
+    fn into_lua(self, lua: &Lua) -> Result<Value> {
+        let mut char_bytes = [0; 4];
+        self.encode_utf8(&mut char_bytes);
+        Ok(Value::String(lua.create_string(&char_bytes[..self.len_utf8()])?))
+    }
+}
+
+impl FromLua for char {
+    fn from_lua(value: Value, _lua: &Lua) -> Result<Self> {
+        let ty = value.type_name();
+        match value {
+            Value::Integer(i) => {
+                cast(i)
+                    .and_then(char::from_u32)
+                    .ok_or_else(|| Error::FromLuaConversionError {
+                        from: ty,
+                        to: "char".to_string(),
+                        message: Some("integer out of range when converting to char".to_string()),
+                    })
+            }
+            Value::String(s) => {
+                let str = s.to_str()?;
+                let mut str_iter = str.chars();
+                match (str_iter.next(), str_iter.next()) {
+                    (Some(char), None) => Ok(char),
+                    _ => Err(Error::FromLuaConversionError {
+                        from: ty,
+                        to: "char".to_string(),
+                        message: Some(
+                            "expected string to have exactly one char when converting to char".to_string(),
+                        ),
+                    }),
+                }
+            }
+            _ => Err(Error::FromLuaConversionError {
+                from: ty,
+                to: Self::type_name(),
+                message: Some("expected string or integer".to_string()),
+            }),
+        }
+    }
+}
+
 #[inline]
 unsafe fn push_bytes_into_stack<T>(this: T, lua: &RawLua) -> Result<()>
 where
@@ -583,15 +808,9 @@ macro_rules! lua_convert_int {
         impl IntoLua for $x {
             #[inline]
             fn into_lua(self, _: &Lua) -> Result<Value> {
-                cast(self)
+                Ok(cast(self)
                     .map(Value::Integer)
-                    .or_else(|| cast(self).map(Value::Number))
-                    // This is impossible error because conversion to Number never fails
-                    .ok_or_else(|| Error::ToLuaConversionError {
-                        from: stringify!($x),
-                        to: "number",
-                        message: Some("out of range".to_owned()),
-                    })
+                    .unwrap_or_else(|| Value::Number(self as ffi::lua_Number)))
             }
 
             #[inline]
@@ -619,7 +838,7 @@ macro_rules! lua_convert_int {
                                 lua.coerce_number(value)?
                                     .ok_or_else(|| Error::FromLuaConversionError {
                                         from: ty,
-                                        to: stringify!($x),
+                                        to: stringify!($x).to_string(),
                                         message: Some(
                                             "expected number or string coercible to number".to_string(),
                                         ),
@@ -630,7 +849,7 @@ macro_rules! lua_convert_int {
                 })
                 .ok_or_else(|| Error::FromLuaConversionError {
                     from: ty,
-                    to: stringify!($x),
+                    to: stringify!($x).to_string(),
                     message: Some("out of range".to_owned()),
                 })
             }
@@ -644,7 +863,7 @@ macro_rules! lua_convert_int {
                     if ok != 0 {
                         return cast(i).ok_or_else(|| Error::FromLuaConversionError {
                             from: "integer",
-                            to: stringify!($x),
+                            to: stringify!($x).to_string(),
                             message: Some("out of range".to_owned()),
                         });
                     }
@@ -674,13 +893,7 @@ macro_rules! lua_convert_float {
         impl IntoLua for $x {
             #[inline]
             fn into_lua(self, _: &Lua) -> Result<Value> {
-                cast(self)
-                    .ok_or_else(|| Error::ToLuaConversionError {
-                        from: stringify!($x),
-                        to: "number",
-                        message: Some("out of range".to_string()),
-                    })
-                    .map(Value::Number)
+                Ok(Value::Number(self as _))
             }
         }
 
@@ -689,33 +902,19 @@ macro_rules! lua_convert_float {
             fn from_lua(value: Value, lua: &Lua) -> Result<Self> {
                 let ty = value.type_name();
                 lua.coerce_number(value)?
+                    .map(|n| n as $x)
                     .ok_or_else(|| Error::FromLuaConversionError {
                         from: ty,
-                        to: stringify!($x),
+                        to: stringify!($x).to_string(),
                         message: Some("expected number or string coercible to number".to_string()),
                     })
-                    .and_then(|n| {
-                        cast(n).ok_or_else(|| Error::FromLuaConversionError {
-                            from: ty,
-                            to: stringify!($x),
-                            message: Some("number out of range".to_string()),
-                        })
-                    })
             }
 
             unsafe fn from_stack(idx: c_int, lua: &RawLua) -> Result<Self> {
                 let state = lua.state();
                 let type_id = ffi::lua_type(state, idx);
                 if type_id == ffi::LUA_TNUMBER {
-                    let mut ok = 0;
-                    let i = ffi::lua_tonumberx(state, idx, &mut ok);
-                    if ok != 0 {
-                        return cast(i).ok_or_else(|| Error::FromLuaConversionError {
-                            from: "number",
-                            to: stringify!($x),
-                            message: Some("out of range".to_owned()),
-                        });
-                    }
+                    return Ok(ffi::lua_tonumber(state, idx) as _);
                 }
                 // Fallback to default
                 Self::from_lua(lua.stack_value(idx, Some(type_id)), lua.lua())
@@ -756,7 +955,7 @@ where
         match value {
             #[cfg(feature = "luau")]
             #[rustfmt::skip]
-            Value::Vector(v) if N == crate::types::Vector::SIZE => unsafe {
+            Value::Vector(v) if N == crate::Vector::SIZE => unsafe {
                 use std::{mem, ptr};
                 let mut arr: [mem::MaybeUninit<T>; N] = mem::MaybeUninit::uninit().assume_init();
                 ptr::write(arr[0].as_mut_ptr() , T::from_lua(Value::Number(v.x() as _), _lua)?);
@@ -771,13 +970,13 @@ where
                 vec.try_into()
                     .map_err(|vec: Vec<T>| Error::FromLuaConversionError {
                         from: "table",
-                        to: "Array",
-                        message: Some(format!("expected table of length {}, got {}", N, vec.len())),
+                        to: Self::type_name(),
+                        message: Some(format!("expected table of length {N}, got {}", vec.len())),
                     })
             }
             _ => Err(Error::FromLuaConversionError {
                 from: value.type_name(),
-                to: "Array",
+                to: Self::type_name(),
                 message: Some("expected table".to_string()),
             }),
         }
@@ -812,7 +1011,7 @@ impl<T: FromLua> FromLua for Vec<T> {
             Value::Table(table) => table.sequence_values().collect(),
             _ => Err(Error::FromLuaConversionError {
                 from: value.type_name(),
-                to: "Vec",
+                to: Self::type_name(),
                 message: Some("expected table".to_string()),
             }),
         }
@@ -834,7 +1033,7 @@ impl<K: Eq + Hash + FromLua, V: FromLua, S: BuildHasher + Default> FromLua for H
         } else {
             Err(Error::FromLuaConversionError {
                 from: value.type_name(),
-                to: "HashMap",
+                to: Self::type_name(),
                 message: Some("expected table".to_string()),
             })
         }
@@ -856,7 +1055,7 @@ impl<K: Ord + FromLua, V: FromLua> FromLua for BTreeMap<K, V> {
         } else {
             Err(Error::FromLuaConversionError {
                 from: value.type_name(),
-                to: "BTreeMap",
+                to: Self::type_name(),
                 message: Some("expected table".to_string()),
             })
         }
@@ -880,7 +1079,7 @@ impl<T: Eq + Hash + FromLua, S: BuildHasher + Default> FromLua for HashSet<T, S>
             Value::Table(table) => table.pairs::<T, Value>().map(|res| res.map(|(k, _)| k)).collect(),
             _ => Err(Error::FromLuaConversionError {
                 from: value.type_name(),
-                to: "HashSet",
+                to: Self::type_name(),
                 message: Some("expected table".to_string()),
             }),
         }
@@ -904,7 +1103,7 @@ impl<T: Ord + FromLua> FromLua for BTreeSet<T> {
             Value::Table(table) => table.pairs::<T, Value>().map(|res| res.map(|(k, _)| k)).collect(),
             _ => Err(Error::FromLuaConversionError {
                 from: value.type_name(),
-                to: "BTreeSet",
+                to: Self::type_name(),
                 message: Some("expected table".to_string()),
             }),
         }
@@ -947,3 +1146,59 @@ impl<T: FromLua> FromLua for Option<T> {
         }
     }
 }
+
+impl<L: IntoLua, R: IntoLua> IntoLua for Either<L, R> {
+    #[inline]
+    fn into_lua(self, lua: &Lua) -> Result<Value> {
+        match self {
+            Either::Left(l) => l.into_lua(lua),
+            Either::Right(r) => r.into_lua(lua),
+        }
+    }
+
+    #[inline]
+    unsafe fn push_into_stack(self, lua: &RawLua) -> Result<()> {
+        match self {
+            Either::Left(l) => l.push_into_stack(lua),
+            Either::Right(r) => r.push_into_stack(lua),
+        }
+    }
+}
+
+impl<L: FromLua, R: FromLua> FromLua for Either<L, R> {
+    #[inline]
+    fn from_lua(value: Value, lua: &Lua) -> Result<Self> {
+        let value_type_name = value.type_name();
+        // Try the left type first
+        match L::from_lua(value.clone(), lua) {
+            Ok(l) => Ok(Either::Left(l)),
+            // Try the right type
+            Err(_) => match R::from_lua(value, lua).map(Either::Right) {
+                Ok(r) => Ok(r),
+                Err(_) => Err(Error::FromLuaConversionError {
+                    from: value_type_name,
+                    to: Self::type_name(),
+                    message: None,
+                }),
+            },
+        }
+    }
+
+    #[inline]
+    unsafe fn from_stack(idx: c_int, lua: &RawLua) -> Result<Self> {
+        match L::from_stack(idx, lua) {
+            Ok(l) => Ok(Either::Left(l)),
+            Err(_) => match R::from_stack(idx, lua).map(Either::Right) {
+                Ok(r) => Ok(r),
+                Err(_) => {
+                    let value_type_name = CStr::from_ptr(ffi::luaL_typename(lua.state(), idx));
+                    Err(Error::FromLuaConversionError {
+                        from: value_type_name.to_str().unwrap(),
+                        to: Self::type_name(),
+                        message: None,
+                    })
+                }
+            },
+        }
+    }
+}

src/debug.rs

@@ -1,72 +1,39 @@
 use std::borrow::Cow;
-use std::cell::UnsafeCell;
-use std::ops::Deref;
-#[cfg(not(feature = "luau"))]
-use std::ops::{BitOr, BitOrAssign};
 use std::os::raw::c_int;
 
-use ffi::lua_Debug;
+use ffi::{lua_Debug, lua_State};
 
+use crate::function::Function;
 use crate::state::RawLua;
-use crate::types::ReentrantMutexGuard;
-use crate::util::{linenumber_to_usize, ptr_to_lossy_str, ptr_to_str};
+use crate::util::{assert_stack, linenumber_to_usize, ptr_to_lossy_str, ptr_to_str, StackGuard};
 
 /// Contains information about currently executing Lua code.
 ///
-/// The `Debug` structure is provided as a parameter to the hook function set with
-/// [`Lua::set_hook`]. You may call the methods on this structure to retrieve information about the
-/// Lua code executing at the time that the hook function was called. Further information can be
-/// found in the Lua [documentation][lua_doc].
+/// You may call the methods on this structure to retrieve information about the Lua code executing
+/// at the specific level. Further information can be found in the Lua [documentation].
 ///
-/// [lua_doc]: https://www.lua.org/manual/5.4/manual.html#lua_Debug
-/// [`Lua::set_hook`]: crate::Lua::set_hook
+/// [documentation]: https://www.lua.org/manual/5.4/manual.html#lua_Debug
 pub struct Debug<'a> {
-    lua: EitherLua<'a>,
-    ar: ActivationRecord,
-    #[cfg(feature = "luau")]
+    state: *mut lua_State,
+    lua: &'a RawLua,
+    #[cfg_attr(not(feature = "luau"), allow(unused))]
     level: c_int,
-}
-
-enum EitherLua<'a> {
-    Owned(ReentrantMutexGuard<'a, RawLua>),
-    #[cfg(not(feature = "luau"))]
-    Borrowed(&'a RawLua),
-}
-
-impl Deref for EitherLua<'_> {
-    type Target = RawLua;
-
-    fn deref(&self) -> &Self::Target {
-        match self {
-            EitherLua::Owned(guard) => guard,
-            #[cfg(not(feature = "luau"))]
-            EitherLua::Borrowed(lua) => lua,
-        }
-    }
+    ar: *mut lua_Debug,
 }
 
 impl<'a> Debug<'a> {
-    // We assume the lock is held when this function is called.
-    #[cfg(not(feature = "luau"))]
-    pub(crate) fn new(lua: &'a RawLua, ar: *mut lua_Debug) -> Self {
+    pub(crate) fn new(lua: &'a RawLua, level: c_int, ar: *mut lua_Debug) -> Self {
         Debug {
-            lua: EitherLua::Borrowed(lua),
-            ar: ActivationRecord::Borrowed(ar),
-        }
-    }
-
-    pub(crate) fn new_owned(guard: ReentrantMutexGuard<'a, RawLua>, _level: c_int, ar: lua_Debug) -> Self {
-        Debug {
-            lua: EitherLua::Owned(guard),
-            ar: ActivationRecord::Owned(UnsafeCell::new(ar)),
-            #[cfg(feature = "luau")]
-            level: _level,
+            state: lua.state(),
+            lua,
+            ar,
+            level,
         }
     }
 
     /// Returns the specific event that triggered the hook.
     ///
-    /// For [Lua 5.1] `DebugEvent::TailCall` is used for return events to indicate a return
+    /// For [Lua 5.1] [`DebugEvent::TailCall`] is used for return events to indicate a return
     /// from a function that did a tail call.
     ///
     /// [Lua 5.1]: https://www.lua.org/manual/5.1/manual.html#pdf-LUA_HOOKTAILRET
@@ -74,7 +41,7 @@ impl<'a> Debug<'a> {
     #[cfg_attr(docsrs, doc(cfg(not(feature = "luau"))))]
     pub fn event(&self) -> DebugEvent {
         unsafe {
-            match (*self.ar.get()).event {
+            match (*self.ar).event {
                 ffi::LUA_HOOKCALL => DebugEvent::Call,
                 ffi::LUA_HOOKRET => DebugEvent::Ret,
                 ffi::LUA_HOOKTAILCALL => DebugEvent::TailCall,
@@ -85,24 +52,48 @@ impl<'a> Debug<'a> {
         }
     }
 
-    /// Corresponds to the `n` what mask.
-    pub fn names(&self) -> DebugNames {
+    /// Returns the function that is running at the given level.
+    ///
+    /// Corresponds to the `f` "what" mask.
+    pub fn function(&self) -> Function {
+        unsafe {
+            let _sg = StackGuard::new(self.state);
+            assert_stack(self.state, 1);
+
+            #[cfg(not(feature = "luau"))]
+            mlua_assert!(
+                ffi::lua_getinfo(self.state, cstr!("f"), self.ar) != 0,
+                "lua_getinfo failed with `f`"
+            );
+            #[cfg(feature = "luau")]
+            mlua_assert!(
+                ffi::lua_getinfo(self.state, self.level, cstr!("f"), self.ar) != 0,
+                "lua_getinfo failed with `f`"
+            );
+
+            ffi::lua_xmove(self.state, self.lua.ref_thread(), 1);
+            Function(self.lua.pop_ref_thread())
+        }
+    }
+
+    /// Corresponds to the `n` "what" mask.
+    pub fn names(&self) -> DebugNames<'_> {
         unsafe {
             #[cfg(not(feature = "luau"))]
             mlua_assert!(
-                ffi::lua_getinfo(self.lua.state(), cstr!("n"), self.ar.get()) != 0,
+                ffi::lua_getinfo(self.state, cstr!("n"), self.ar) != 0,
                 "lua_getinfo failed with `n`"
             );
             #[cfg(feature = "luau")]
             mlua_assert!(
-                ffi::lua_getinfo(self.lua.state(), self.level, cstr!("n"), self.ar.get()) != 0,
+                ffi::lua_getinfo(self.state, self.level, cstr!("n"), self.ar) != 0,
                 "lua_getinfo failed with `n`"
             );
 
             DebugNames {
-                name: ptr_to_lossy_str((*self.ar.get()).name),
+                name: ptr_to_lossy_str((*self.ar).name),
                 #[cfg(not(feature = "luau"))]
-                name_what: match ptr_to_str((*self.ar.get()).namewhat) {
+                name_what: match ptr_to_str((*self.ar).namewhat) {
                     Some("") => None,
                     val => val,
                 },
@@ -112,118 +103,110 @@ impl<'a> Debug<'a> {
         }
     }
 
-    /// Corresponds to the `S` what mask.
-    pub fn source(&self) -> DebugSource {
+    /// Corresponds to the `S` "what" mask.
+    pub fn source(&self) -> DebugSource<'_> {
         unsafe {
             #[cfg(not(feature = "luau"))]
             mlua_assert!(
-                ffi::lua_getinfo(self.lua.state(), cstr!("S"), self.ar.get()) != 0,
+                ffi::lua_getinfo(self.state, cstr!("S"), self.ar) != 0,
                 "lua_getinfo failed with `S`"
             );
             #[cfg(feature = "luau")]
             mlua_assert!(
-                ffi::lua_getinfo(self.lua.state(), self.level, cstr!("s"), self.ar.get()) != 0,
+                ffi::lua_getinfo(self.state, self.level, cstr!("s"), self.ar) != 0,
                 "lua_getinfo failed with `s`"
             );
 
             DebugSource {
-                source: ptr_to_lossy_str((*self.ar.get()).source),
+                source: ptr_to_lossy_str((*self.ar).source),
                 #[cfg(not(feature = "luau"))]
-                short_src: ptr_to_lossy_str((*self.ar.get()).short_src.as_ptr()),
+                short_src: ptr_to_lossy_str((*self.ar).short_src.as_ptr()),
                 #[cfg(feature = "luau")]
-                short_src: ptr_to_lossy_str((*self.ar.get()).short_src),
-                line_defined: linenumber_to_usize((*self.ar.get()).linedefined),
+                short_src: ptr_to_lossy_str((*self.ar).short_src),
+                line_defined: linenumber_to_usize((*self.ar).linedefined),
                 #[cfg(not(feature = "luau"))]
-                last_line_defined: linenumber_to_usize((*self.ar.get()).lastlinedefined),
+                last_line_defined: linenumber_to_usize((*self.ar).lastlinedefined),
                 #[cfg(feature = "luau")]
                 last_line_defined: None,
-                what: ptr_to_str((*self.ar.get()).what).unwrap_or("main"),
+                what: ptr_to_str((*self.ar).what).unwrap_or("main"),
             }
         }
     }
 
-    /// Corresponds to the `l` what mask. Returns the current line.
+    #[doc(hidden)]
+    #[deprecated(note = "Use `current_line` instead")]
     pub fn curr_line(&self) -> i32 {
+        self.current_line().map(|n| n as i32).unwrap_or(-1)
+    }
+
+    /// Corresponds to the `l` "what" mask. Returns the current line.
+    pub fn current_line(&self) -> Option<usize> {
         unsafe {
             #[cfg(not(feature = "luau"))]
             mlua_assert!(
-                ffi::lua_getinfo(self.lua.state(), cstr!("l"), self.ar.get()) != 0,
+                ffi::lua_getinfo(self.state, cstr!("l"), self.ar) != 0,
                 "lua_getinfo failed with `l`"
             );
             #[cfg(feature = "luau")]
             mlua_assert!(
-                ffi::lua_getinfo(self.lua.state(), self.level, cstr!("l"), self.ar.get()) != 0,
+                ffi::lua_getinfo(self.state, self.level, cstr!("l"), self.ar) != 0,
                 "lua_getinfo failed with `l`"
             );
 
-            (*self.ar.get()).currentline
+            linenumber_to_usize((*self.ar).currentline)
         }
     }
 
-    /// Corresponds to the `t` what mask. Returns true if the hook is in a function tail call, false
-    /// otherwise.
-    #[cfg(not(feature = "luau"))]
-    #[cfg_attr(docsrs, doc(cfg(not(feature = "luau"))))]
+    /// Corresponds to the `t` "what" mask. Returns true if the hook is in a function tail call,
+    /// false otherwise.
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(any(feature = "lua54", feature = "lua53", feature = "lua52")))
+    )]
     pub fn is_tail_call(&self) -> bool {
         unsafe {
             mlua_assert!(
-                ffi::lua_getinfo(self.lua.state(), cstr!("t"), self.ar.get()) != 0,
+                ffi::lua_getinfo(self.state, cstr!("t"), self.ar) != 0,
                 "lua_getinfo failed with `t`"
             );
-            (*self.ar.get()).currentline != 0
+            (*self.ar).istailcall != 0
         }
     }
 
-    /// Corresponds to the `u` what mask.
+    /// Corresponds to the `u` "what" mask.
     pub fn stack(&self) -> DebugStack {
         unsafe {
             #[cfg(not(feature = "luau"))]
             mlua_assert!(
-                ffi::lua_getinfo(self.lua.state(), cstr!("u"), self.ar.get()) != 0,
+                ffi::lua_getinfo(self.state, cstr!("u"), self.ar) != 0,
                 "lua_getinfo failed with `u`"
             );
             #[cfg(feature = "luau")]
             mlua_assert!(
-                ffi::lua_getinfo(self.lua.state(), self.level, cstr!("a"), self.ar.get()) != 0,
-                "lua_getinfo failed with `a`"
+                ffi::lua_getinfo(self.state, self.level, cstr!("au"), self.ar) != 0,
+                "lua_getinfo failed with `au`"
             );
 
             #[cfg(not(feature = "luau"))]
             let stack = DebugStack {
-                num_ups: (*self.ar.get()).nups as _,
+                num_ups: (*self.ar).nups as _,
                 #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
-                num_params: (*self.ar.get()).nparams as _,
+                num_params: (*self.ar).nparams as _,
                 #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
-                is_vararg: (*self.ar.get()).isvararg != 0,
+                is_vararg: (*self.ar).isvararg != 0,
             };
             #[cfg(feature = "luau")]
             let stack = DebugStack {
-                num_ups: (*self.ar.get()).nupvals as i32,
-                num_params: (*self.ar.get()).nparams as i32,
-                is_vararg: (*self.ar.get()).isvararg != 0,
+                num_ups: (*self.ar).nupvals,
+                num_params: (*self.ar).nparams,
+                is_vararg: (*self.ar).isvararg != 0,
             };
             stack
         }
     }
 }
 
-enum ActivationRecord {
-    #[cfg(not(feature = "luau"))]
-    Borrowed(*mut lua_Debug),
-    Owned(UnsafeCell<lua_Debug>),
-}
-
-impl ActivationRecord {
-    #[inline]
-    fn get(&self) -> *mut lua_Debug {
-        match self {
-            #[cfg(not(feature = "luau"))]
-            ActivationRecord::Borrowed(x) => *x,
-            ActivationRecord::Owned(x) => x.get(),
-        }
-    }
-}
-
 /// Represents a specific event that triggered the hook.
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum DebugEvent {
@@ -262,12 +245,21 @@ pub struct DebugSource<'a> {
 
 #[derive(Copy, Clone, Debug)]
 pub struct DebugStack {
-    pub num_ups: i32,
-    /// Requires `feature = "lua54/lua53/lua52/luau"`
+    /// Number of upvalues.
+    pub num_ups: u8,
+    /// Number of parameters.
     #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52", feature = "luau"))]
-    pub num_params: i32,
-    /// Requires `feature = "lua54/lua53/lua52/luau"`
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(any(feature = "lua54", feature = "lua53", feature = "lua52", feature = "luau")))
+    )]
+    pub num_params: u8,
+    /// Whether the function is a vararg function.
     #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52", feature = "luau"))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(any(feature = "lua54", feature = "lua53", feature = "lua52", feature = "luau")))
+    )]
     pub is_vararg: bool,
 }
 
@@ -373,7 +365,7 @@ impl HookTriggers {
 }
 
 #[cfg(not(feature = "luau"))]
-impl BitOr for HookTriggers {
+impl std::ops::BitOr for HookTriggers {
     type Output = Self;
 
     fn bitor(mut self, rhs: Self) -> Self::Output {
@@ -388,7 +380,7 @@ impl BitOr for HookTriggers {
 }
 
 #[cfg(not(feature = "luau"))]
-impl BitOrAssign for HookTriggers {
+impl std::ops::BitOrAssign for HookTriggers {
     fn bitor_assign(&mut self, rhs: Self) {
         *self = *self | rhs;
     }

src/error.rs

@@ -9,6 +9,12 @@ use std::sync::Arc;
 
 use crate::private::Sealed;
 
+#[cfg(feature = "error-send")]
+type DynStdError = dyn StdError + Send + Sync;
+
+#[cfg(not(feature = "error-send"))]
+type DynStdError = dyn StdError;
+
 /// Error type returned by `mlua` methods.
 #[derive(Debug, Clone)]
 #[non_exhaustive]
@@ -42,11 +48,11 @@ pub enum Error {
     GarbageCollectorError(StdString),
     /// Potentially unsafe action in safe mode.
     SafetyError(StdString),
-    /// Setting memory limit is not available.
+    /// Memory control is not available.
     ///
     /// This error can only happen when Lua state was not created by us and does not have the
     /// custom allocator attached.
-    MemoryLimitNotAvailable,
+    MemoryControlNotAvailable,
     /// A mutable callback has triggered Lua code that has called the same mutable callback again.
     ///
     /// This is an error because a mutable callback can only be borrowed mutably once.
@@ -61,10 +67,12 @@ pub enum Error {
     ///
     /// Due to the way `mlua` works, it should not be directly possible to run out of stack space
     /// during normal use. The only way that this error can be triggered is if a `Function` is
-    /// called with a huge number of arguments, or a rust callback returns a huge number of return
+    /// called with a huge number of arguments, or a Rust callback returns a huge number of return
     /// values.
     StackError,
-    /// Too many arguments to `Function::bind`.
+    /// Too many arguments to [`Function::bind`].
+    ///
+    /// [`Function::bind`]: crate::Function::bind
     BindError,
     /// Bad argument received from Lua (usually when calling a function).
     ///
@@ -83,7 +91,7 @@ pub enum Error {
     /// A Rust value could not be converted to a Lua value.
     ToLuaConversionError {
         /// Name of the Rust type that could not be converted.
-        from: &'static str,
+        from: String,
         /// Name of the Lua type that could not be created.
         to: &'static str,
         /// A message indicating why the conversion failed in more detail.
@@ -94,7 +102,7 @@ pub enum Error {
         /// Name of the Lua type that could not be converted.
         from: &'static str,
         /// Name of the Rust type that could not be created.
-        to: &'static str,
+        to: String,
         /// A string containing more detailed error information.
         message: Option<StdString>,
     },
@@ -175,12 +183,12 @@ pub enum Error {
     /// and returned again.
     PreviouslyResumedPanic,
     /// Serialization error.
-    #[cfg(feature = "serialize")]
-    #[cfg_attr(docsrs, doc(cfg(feature = "serialize")))]
+    #[cfg(feature = "serde")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
     SerializeError(StdString),
     /// Deserialization error.
-    #[cfg(feature = "serialize")]
-    #[cfg_attr(docsrs, doc(cfg(feature = "serialize")))]
+    #[cfg(feature = "serde")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
     DeserializeError(StdString),
     /// A custom error.
     ///
@@ -189,7 +197,7 @@ pub enum Error {
     /// Returning `Err(ExternalError(...))` from a Rust callback will raise the error as a Lua
     /// error. The Rust code that originally invoked the Lua code then receives a `CallbackError`,
     /// from which the original error (and a stack traceback) can be recovered.
-    ExternalError(Arc<dyn StdError + Send + Sync>),
+    ExternalError(Arc<DynStdError>),
     /// An error with additional context.
     WithContext {
         /// A string containing additional context.
@@ -205,21 +213,21 @@ pub type Result<T> = StdResult<T, Error>;
 #[cfg(not(tarpaulin_include))]
 impl fmt::Display for Error {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
-        match *self {
-            Error::SyntaxError { ref message, .. } => write!(fmt, "syntax error: {message}"),
-            Error::RuntimeError(ref msg) => write!(fmt, "runtime error: {msg}"),
-            Error::MemoryError(ref msg) => {
+        match self {
+            Error::SyntaxError { message, .. } => write!(fmt, "syntax error: {message}"),
+            Error::RuntimeError(msg) => write!(fmt, "runtime error: {msg}"),
+            Error::MemoryError(msg) => {
                 write!(fmt, "memory error: {msg}")
             }
             #[cfg(any(feature = "lua53", feature = "lua52"))]
-            Error::GarbageCollectorError(ref msg) => {
+            Error::GarbageCollectorError(msg) => {
                 write!(fmt, "garbage collector error: {msg}")
             }
-            Error::SafetyError(ref msg) => {
+            Error::SafetyError(msg) => {
                 write!(fmt, "safety error: {msg}")
             },
-            Error::MemoryLimitNotAvailable => {
-                write!(fmt, "setting memory limit is not available")
+            Error::MemoryControlNotAvailable => {
+                write!(fmt, "memory control is not available")
             }
             Error::RecursiveMutCallback => write!(fmt, "mutable callback called recursively"),
             Error::CallbackDestructed => write!(
@@ -234,7 +242,7 @@ impl fmt::Display for Error {
                 fmt,
                 "too many arguments to Function::bind"
             ),
-            Error::BadArgument { ref to, pos, ref name, ref cause } => {
+            Error::BadArgument { to, pos, name, cause } => {
                 if let Some(name) = name {
                     write!(fmt, "bad argument `{name}`")?;
                 } else {
@@ -245,18 +253,18 @@ impl fmt::Display for Error {
                 }
                 write!(fmt, ": {cause}")
             },
-            Error::ToLuaConversionError { from, to, ref message } => {
+            Error::ToLuaConversionError { from, to, message } => {
                 write!(fmt, "error converting {from} to Lua {to}")?;
-                match *message {
+                match message {
                     None => Ok(()),
-                    Some(ref message) => write!(fmt, " ({message})"),
+                    Some(message) => write!(fmt, " ({message})"),
                 }
             }
-            Error::FromLuaConversionError { from, to, ref message } => {
+            Error::FromLuaConversionError { from, to, message } => {
                 write!(fmt, "error converting Lua {from} to {to}")?;
-                match *message {
+                match message {
                     None => Ok(()),
-                    Some(ref message) => write!(fmt, " ({message})"),
+                    Some(message) => write!(fmt, " ({message})"),
                 }
             }
             Error::CoroutineUnresumable => write!(fmt, "coroutine is non-resumable"),
@@ -264,21 +272,21 @@ impl fmt::Display for Error {
             Error::UserDataDestructed => write!(fmt, "userdata has been destructed"),
             Error::UserDataBorrowError => write!(fmt, "error borrowing userdata"),
             Error::UserDataBorrowMutError => write!(fmt, "error mutably borrowing userdata"),
-            Error::MetaMethodRestricted(ref method) => write!(fmt, "metamethod {method} is restricted"),
-            Error::MetaMethodTypeError { ref method, type_name, ref message } => {
+            Error::MetaMethodRestricted(method) => write!(fmt, "metamethod {method} is restricted"),
+            Error::MetaMethodTypeError { method, type_name, message } => {
                 write!(fmt, "metamethod {method} has unsupported type {type_name}")?;
-                match *message {
+                match message {
                     None => Ok(()),
-                    Some(ref message) => write!(fmt, " ({message})"),
+                    Some(message) => write!(fmt, " ({message})"),
                 }
             }
             Error::MismatchedRegistryKey => {
                 write!(fmt, "RegistryKey used from different Lua state")
             }
-            Error::CallbackError { ref cause, ref traceback } => {
+            Error::CallbackError { cause, traceback } => {
                 // Trace errors down to the root
                 let (mut cause, mut full_traceback) = (cause, None);
-                while let Error::CallbackError { cause: ref cause2, traceback: ref traceback2 } = **cause {
+                while let Error::CallbackError { cause: cause2, traceback: traceback2 } = &**cause {
                     cause = cause2;
                     full_traceback = Some(traceback2);
                 }
@@ -301,16 +309,16 @@ impl fmt::Display for Error {
             Error::PreviouslyResumedPanic => {
                 write!(fmt, "previously resumed panic returned again")
             }
-            #[cfg(feature = "serialize")]
-            Error::SerializeError(ref err) => {
+            #[cfg(feature = "serde")]
+            Error::SerializeError(err) => {
                 write!(fmt, "serialize error: {err}")
             },
-            #[cfg(feature = "serialize")]
-            Error::DeserializeError(ref err) => {
+            #[cfg(feature = "serde")]
+            Error::DeserializeError(err) => {
                 write!(fmt, "deserialize error: {err}")
             },
-            Error::ExternalError(ref err) => write!(fmt, "{err}"),
-            Error::WithContext { ref context, ref cause } => {
+            Error::ExternalError(err) => err.fmt(fmt),
+            Error::WithContext { context, cause } => {
                 writeln!(fmt, "{context}")?;
                 write!(fmt, "{cause}")
             }
@@ -320,18 +328,15 @@ impl fmt::Display for Error {
 
 impl StdError for Error {
     fn source(&self) -> Option<&(dyn StdError + 'static)> {
-        match *self {
+        match self {
             // An error type with a source error should either return that error via source or
             // include that source's error message in its own Display output, but never both.
             // https://blog.rust-lang.org/inside-rust/2021/07/01/What-the-error-handling-project-group-is-working-towards.html
             // Given that we include source to fmt::Display implementation for `CallbackError`, this call
             // returns nothing.
             Error::CallbackError { .. } => None,
-            Error::ExternalError(ref err) => err.source(),
-            Error::WithContext { ref cause, .. } => match cause.as_ref() {
-                Error::ExternalError(err) => err.source(),
-                _ => None,
-            },
+            Error::ExternalError(err) => err.source(),
+            Error::WithContext { cause, .. } => Self::source(cause),
             _ => None,
         }
     }
@@ -346,7 +351,7 @@ impl Error {
 
     /// Wraps an external error object.
     #[inline]
-    pub fn external<T: Into<Box<dyn StdError + Send + Sync>>>(err: T) -> Self {
+    pub fn external<T: Into<Box<DynStdError>>>(err: T) -> Self {
         Error::ExternalError(err.into().into())
     }
 
@@ -357,10 +362,25 @@ impl Error {
     {
         match self {
             Error::ExternalError(err) => err.downcast_ref(),
-            Error::WithContext { cause, .. } => match cause.as_ref() {
-                Error::ExternalError(err) => err.downcast_ref(),
-                _ => None,
-            },
+            Error::WithContext { cause, .. } => Self::downcast_ref(cause),
+            _ => None,
+        }
+    }
+
+    /// An iterator over the chain of nested errors wrapped by this Error.
+    pub fn chain(&self) -> impl Iterator<Item = &(dyn StdError + 'static)> {
+        Chain {
+            root: self,
+            current: None,
+        }
+    }
+
+    /// Returns the parent of this error.
+    #[doc(hidden)]
+    pub fn parent(&self) -> Option<&Error> {
+        match self {
+            Error::CallbackError { cause, .. } => Some(cause.as_ref()),
+            Error::WithContext { cause, .. } => Some(cause.as_ref()),
             _ => None,
         }
     }
@@ -374,15 +394,15 @@ impl Error {
         }
     }
 
-    pub(crate) fn from_lua_conversion<'a>(
+    pub(crate) fn from_lua_conversion(
         from: &'static str,
-        to: &'static str,
-        message: impl Into<Option<&'a str>>,
+        to: impl ToString,
+        message: impl Into<Option<String>>,
     ) -> Self {
         Error::FromLuaConversionError {
             from,
-            to,
-            message: message.into().map(|s| s.into()),
+            to: to.to_string(),
+            message: message.into(),
         }
     }
 }
@@ -392,7 +412,7 @@ pub trait ExternalError {
     fn into_lua_err(self) -> Error;
 }
 
-impl<E: Into<Box<dyn StdError + Send + Sync>>> ExternalError for E {
+impl<E: Into<Box<DynStdError>>> ExternalError for E {
     fn into_lua_err(self) -> Error {
         Error::external(self)
     }
@@ -446,7 +466,7 @@ impl ErrorContext for Error {
     }
 }
 
-impl<T> ErrorContext for StdResult<T, Error> {
+impl<T> ErrorContext for Result<T> {
     fn context<C: fmt::Display>(self, context: C) -> Self {
         self.map_err(|err| err.context(context))
     }
@@ -474,16 +494,77 @@ impl From<Utf8Error> for Error {
     }
 }
 
-#[cfg(feature = "serialize")]
+#[cfg(feature = "serde")]
 impl serde::ser::Error for Error {
     fn custom<T: fmt::Display>(msg: T) -> Self {
         Self::SerializeError(msg.to_string())
     }
 }
 
-#[cfg(feature = "serialize")]
+#[cfg(feature = "serde")]
 impl serde::de::Error for Error {
     fn custom<T: fmt::Display>(msg: T) -> Self {
         Self::DeserializeError(msg.to_string())
     }
 }
+
+#[cfg(feature = "anyhow")]
+impl From<anyhow::Error> for Error {
+    fn from(err: anyhow::Error) -> Self {
+        match err.downcast::<Self>() {
+            Ok(err) => err,
+            Err(err) => Error::external(err),
+        }
+    }
+}
+
+struct Chain<'a> {
+    root: &'a Error,
+    current: Option<&'a (dyn StdError + 'static)>,
+}
+
+impl<'a> Iterator for Chain<'a> {
+    type Item = &'a (dyn StdError + 'static);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        loop {
+            let error: Option<&dyn StdError> = match self.current {
+                None => {
+                    self.current = Some(self.root);
+                    self.current
+                }
+                Some(current) => match current.downcast_ref::<Error>()? {
+                    Error::BadArgument { cause, .. }
+                    | Error::CallbackError { cause, .. }
+                    | Error::WithContext { cause, .. } => {
+                        self.current = Some(&**cause);
+                        self.current
+                    }
+                    Error::ExternalError(err) => {
+                        self.current = Some(&**err);
+                        self.current
+                    }
+                    _ => None,
+                },
+            };
+
+            // Skip `ExternalError` as it only wraps the underlying error
+            // without meaningful context
+            if let Some(Error::ExternalError(_)) = error?.downcast_ref::<Error>() {
+                continue;
+            }
+
+            return self.current;
+        }
+    }
+}
+
+#[cfg(test)]
+mod assertions {
+    use super::*;
+
+    #[cfg(not(feature = "error-send"))]
+    static_assertions::assert_not_impl_any!(Error: Send, Sync);
+    #[cfg(feature = "send")]
+    static_assertions::assert_impl_all!(Error: Send, Sync);
+}

src/function.rs

@@ -5,20 +5,25 @@ use std::{mem, ptr, slice};
 use crate::error::{Error, Result};
 use crate::state::Lua;
 use crate::table::Table;
-use crate::types::{Callback, MaybeSend, ValueRef};
+use crate::traits::{FromLuaMulti, IntoLua, IntoLuaMulti, LuaNativeFn, LuaNativeFnMut};
+use crate::types::{Callback, LuaType, MaybeSend, ValueRef};
 use crate::util::{
     assert_stack, check_stack, linenumber_to_usize, pop_error, ptr_to_lossy_str, ptr_to_str, StackGuard,
 };
-use crate::value::{FromLuaMulti, IntoLua, IntoLuaMulti, Value};
+use crate::value::Value;
 
 #[cfg(feature = "async")]
 use {
+    crate::thread::AsyncThread,
+    crate::traits::LuaNativeAsyncFn,
     crate::types::AsyncCallback,
     std::future::{self, Future},
+    std::pin::Pin,
+    std::task::{Context, Poll},
 };
 
 /// Handle to an internal Lua function.
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, PartialEq)]
 pub struct Function(pub(crate) ValueRef);
 
 /// Contains information about a function.
@@ -126,9 +131,8 @@ impl Function {
     /// Returns a future that, when polled, calls `self`, passing `args` as function arguments,
     /// and drives the execution.
     ///
-    /// Internally it wraps the function to an [`AsyncThread`].
-    ///
-    /// Requires `feature = "async"`
+    /// Internally it wraps the function to an [`AsyncThread`]. The returned type implements
+    /// `Future<Output = Result<R>>` and can be awaited.
     ///
     /// # Examples
     ///
@@ -144,7 +148,7 @@ impl Function {
     ///     Ok(())
     /// })?;
     ///
-    /// sleep.call_async(10).await?;
+    /// sleep.call_async::<()>(10).await?;
     ///
     /// # Ok(())
     /// # }
@@ -153,19 +157,18 @@ impl Function {
     /// [`AsyncThread`]: crate::AsyncThread
     #[cfg(feature = "async")]
     #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
-    pub fn call_async<R>(&self, args: impl IntoLuaMulti) -> impl Future<Output = Result<R>>
+    pub fn call_async<R>(&self, args: impl IntoLuaMulti) -> AsyncCallFuture<R>
     where
         R: FromLuaMulti,
     {
         let lua = self.0.lua.lock();
-        let thread_res = unsafe {
-            lua.create_recycled_thread(self).map(|th| {
-                let mut th = th.into_async(args);
+        AsyncCallFuture(unsafe {
+            lua.create_recycled_thread(self).and_then(|th| {
+                let mut th = th.into_async(args)?;
                 th.set_recyclable(true);
-                th
+                Ok(th)
             })
-        };
-        async move { thread_res?.await }
+        })
     }
 
     /// Returns a function that, when called, calls `self`, passing `args` as the first set of
@@ -250,7 +253,7 @@ impl Function {
             "#,
         )
         .try_cache()
-        .set_name("__mlua_bind")
+        .set_name("=__mlua_bind")
         .call((self, args_wrapper))
     }
 
@@ -278,7 +281,7 @@ impl Function {
                 // Traverse upvalues until we find the _ENV one
                 match ffi::lua_getupvalue(state, -1, i) {
                     s if s.is_null() => break,
-                    s if std::ffi::CStr::from_ptr(s as _).to_bytes() == b"_ENV" => break,
+                    s if std::ffi::CStr::from_ptr(s as _) == c"_ENV" => break,
                     _ => ffi::lua_pop(state, 1),
                 }
             }
@@ -317,7 +320,7 @@ impl Function {
             for i in 1..=255 {
                 match ffi::lua_getupvalue(state, -1, i) {
                     s if s.is_null() => return Ok(false),
-                    s if std::ffi::CStr::from_ptr(s as _).to_bytes() == b"_ENV" => {
+                    s if std::ffi::CStr::from_ptr(s as _) == c"_ENV" => {
                         ffi::lua_pop(state, 1);
                         // Create an anonymous function with the new environment
                         let f_with_env = lua
@@ -387,9 +390,9 @@ impl Function {
     /// If `strip` is true, the binary representation may not include all debug information
     /// about the function, to save space.
     ///
-    /// For Luau a [Compiler] can be used to compile Lua chunks to bytecode.
+    /// For Luau a [`Compiler`] can be used to compile Lua chunks to bytecode.
     ///
-    /// [Compiler]: crate::chunk::Compiler
+    /// [`Compiler`]: crate::chunk::Compiler
     #[cfg(not(feature = "luau"))]
     #[cfg_attr(docsrs, doc(cfg(not(feature = "luau"))))]
     pub fn dump(&self, strip: bool) -> Vec<u8> {
@@ -428,12 +431,10 @@ impl Function {
     ///
     /// Recording of coverage information is controlled by [`Compiler::set_coverage_level`] option.
     ///
-    /// Requires `feature = "luau"`
-    ///
     /// [`Compiler::set_coverage_level`]: crate::chunk::Compiler::set_coverage_level
     #[cfg(any(feature = "luau", doc))]
     #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
-    pub fn coverage<F>(&self, mut func: F)
+    pub fn coverage<F>(&self, func: F)
     where
         F: FnMut(CoverageInfo),
     {
@@ -453,13 +454,16 @@ impl Function {
             } else {
                 None
             };
-            let rust_callback = &mut *(data as *mut F);
-            rust_callback(CoverageInfo {
-                function,
-                line_defined,
-                depth,
-                hits: slice::from_raw_parts(hits, size).to_vec(),
-            });
+            let rust_callback = &*(data as *const RefCell<F>);
+            if let Ok(mut rust_callback) = rust_callback.try_borrow_mut() {
+                // Call the Rust callback with CoverageInfo
+                rust_callback(CoverageInfo {
+                    function,
+                    line_defined,
+                    depth,
+                    hits: slice::from_raw_parts(hits, size).to_vec(),
+                });
+            }
         }
 
         let lua = self.0.lua.lock();
@@ -469,7 +473,8 @@ impl Function {
             assert_stack(state, 1);
 
             lua.push_ref(&self.0);
-            let func_ptr = &mut func as *mut F as *mut c_void;
+            let func = RefCell::new(func);
+            let func_ptr = &func as *const RefCell<F> as *mut c_void;
             ffi::lua_getcoverage(state, -1, func_ptr, callback::<F>);
         }
     }
@@ -488,65 +493,99 @@ impl Function {
     ///
     /// Copies the function prototype and all its upvalues to the
     /// newly created function.
-    ///
     /// This function returns shallow clone (same handle) for Rust/C functions.
-    /// Requires `feature = "luau"`
-    #[cfg(feature = "luau")]
+    #[cfg(any(feature = "luau", doc))]
     #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
-    pub fn deep_clone(&self) -> Self {
+    pub fn deep_clone(&self) -> Result<Self> {
         let lua = self.0.lua.lock();
-        let ref_thread = lua.ref_thread();
+        let state = lua.state();
         unsafe {
-            if ffi::lua_iscfunction(ref_thread, self.0.index) != 0 {
-                return self.clone();
+            let _sg = StackGuard::new(state);
+            check_stack(state, 2)?;
+
+            lua.push_ref(&self.0);
+            if ffi::lua_iscfunction(state, -1) != 0 {
+                return Ok(self.clone());
             }
 
-            ffi::lua_clonefunction(ref_thread, self.0.index);
-            Function(lua.pop_ref_thread())
+            if lua.unlikely_memory_error() {
+                ffi::lua_clonefunction(state, -1);
+            } else {
+                protect_lua!(state, 1, 1, fn(state) ffi::lua_clonefunction(state, -1))?;
+            }
+            Ok(Function(lua.pop_ref()))
         }
     }
 }
 
-impl PartialEq for Function {
-    fn eq(&self, other: &Self) -> bool {
-        self.0 == other.0
-    }
-}
-
-pub(crate) struct WrappedFunction(pub(crate) Callback);
+struct WrappedFunction(pub(crate) Callback);
 
 #[cfg(feature = "async")]
-pub(crate) struct WrappedAsyncFunction(pub(crate) AsyncCallback);
+struct WrappedAsyncFunction(pub(crate) AsyncCallback);
 
 impl Function {
     /// Wraps a Rust function or closure, returning an opaque type that implements [`IntoLua`]
     /// trait.
     #[inline]
-    pub fn wrap<A, R, F>(func: F) -> impl IntoLua
+    pub fn wrap<F, A, R>(func: F) -> impl IntoLua
     where
+        F: LuaNativeFn<A, Output = Result<R>> + MaybeSend + 'static,
         A: FromLuaMulti,
         R: IntoLuaMulti,
-        F: Fn(&Lua, A) -> Result<R> + MaybeSend + 'static,
     {
         WrappedFunction(Box::new(move |lua, nargs| unsafe {
             let args = A::from_stack_args(nargs, 1, None, lua)?;
-            func(lua.lua(), args)?.push_into_stack_multi(lua)
+            func.call(args)?.push_into_stack_multi(lua)
         }))
     }
 
     /// Wraps a Rust mutable closure, returning an opaque type that implements [`IntoLua`] trait.
-    #[inline]
-    pub fn wrap_mut<A, R, F>(func: F) -> impl IntoLua
+    pub fn wrap_mut<F, A, R>(func: F) -> impl IntoLua
     where
+        F: LuaNativeFnMut<A, Output = Result<R>> + MaybeSend + 'static,
         A: FromLuaMulti,
         R: IntoLuaMulti,
-        F: FnMut(&Lua, A) -> Result<R> + MaybeSend + 'static,
     {
         let func = RefCell::new(func);
         WrappedFunction(Box::new(move |lua, nargs| unsafe {
             let mut func = func.try_borrow_mut().map_err(|_| Error::RecursiveMutCallback)?;
             let args = A::from_stack_args(nargs, 1, None, lua)?;
-            func(lua.lua(), args)?.push_into_stack_multi(lua)
+            func.call(args)?.push_into_stack_multi(lua)
+        }))
+    }
+
+    /// Wraps a Rust function or closure, returning an opaque type that implements [`IntoLua`]
+    /// trait.
+    ///
+    /// This function is similar to [`Function::wrap`] but any returned `Result` will be converted
+    /// to a `ok, err` tuple without throwing an exception.
+    #[inline]
+    pub fn wrap_raw<F, A>(func: F) -> impl IntoLua
+    where
+        F: LuaNativeFn<A> + MaybeSend + 'static,
+        A: FromLuaMulti,
+    {
+        WrappedFunction(Box::new(move |lua, nargs| unsafe {
+            let args = A::from_stack_args(nargs, 1, None, lua)?;
+            func.call(args).push_into_stack_multi(lua)
+        }))
+    }
+
+    /// Wraps a Rust mutable closure, returning an opaque type that implements [`IntoLua`] trait.
+    ///
+    /// This function is similar to [`Function::wrap_mut`] but any returned `Result` will be
+    /// converted to a `ok, err` tuple without throwing an exception.
+    #[inline]
+    pub fn wrap_raw_mut<F, A>(func: F) -> impl IntoLua
+    where
+        F: LuaNativeFnMut<A> + MaybeSend + 'static,
+        A: FromLuaMulti,
+    {
+        let func = RefCell::new(func);
+        WrappedFunction(Box::new(move |lua, nargs| unsafe {
+            let mut func = func.try_borrow_mut().map_err(|_| Error::RecursiveMutCallback)?;
+            let args = A::from_stack_args(nargs, 1, None, lua)?;
+            func.call(args).push_into_stack_multi(lua)
         }))
     }
 
@@ -554,23 +593,45 @@ impl Function {
     /// trait.
     #[cfg(feature = "async")]
     #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
-    pub fn wrap_async<A, R, F, FR>(func: F) -> impl IntoLua
+    pub fn wrap_async<F, A, R>(func: F) -> impl IntoLua
     where
+        F: LuaNativeAsyncFn<A, Output = Result<R>> + MaybeSend + 'static,
         A: FromLuaMulti,
         R: IntoLuaMulti,
-        F: Fn(Lua, A) -> FR + MaybeSend + 'static,
-        FR: Future<Output = Result<R>> + MaybeSend + 'static,
     {
         WrappedAsyncFunction(Box::new(move |rawlua, nargs| unsafe {
             let args = match A::from_stack_args(nargs, 1, None, rawlua) {
                 Ok(args) => args,
                 Err(e) => return Box::pin(future::ready(Err(e))),
             };
-            let lua = rawlua.lua().clone();
-            let fut = func(lua.clone(), args);
+            let lua = rawlua.lua();
+            let fut = func.call(args);
             Box::pin(async move { fut.await?.push_into_stack_multi(lua.raw_lua()) })
         }))
     }
+
+    /// Wraps a Rust async function or closure, returning an opaque type that implements [`IntoLua`]
+    /// trait.
+    ///
+    /// This function is similar to [`Function::wrap_async`] but any returned `Result` will be
+    /// converted to a `ok, err` tuple without throwing an exception.
+    #[cfg(feature = "async")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
+    pub fn wrap_raw_async<F, A>(func: F) -> impl IntoLua
+    where
+        F: LuaNativeAsyncFn<A> + MaybeSend + 'static,
+        A: FromLuaMulti,
+    {
+        WrappedAsyncFunction(Box::new(move |rawlua, nargs| unsafe {
+            let args = match A::from_stack_args(nargs, 1, None, rawlua) {
+                Ok(args) => args,
+                Err(e) => return Box::pin(future::ready(Err(e))),
+            };
+            let lua = rawlua.lua();
+            let fut = func.call(args);
+            Box::pin(async move { fut.await.push_into_stack_multi(lua.raw_lua()) })
+        }))
+    }
 }
 
 impl IntoLua for WrappedFunction {
@@ -588,6 +649,38 @@ impl IntoLua for WrappedAsyncFunction {
     }
 }
 
+impl LuaType for Function {
+    const TYPE_ID: c_int = ffi::LUA_TFUNCTION;
+}
+
+#[cfg(feature = "async")]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
+pub struct AsyncCallFuture<R: FromLuaMulti>(Result<AsyncThread<R>>);
+
+#[cfg(feature = "async")]
+impl<R: FromLuaMulti> AsyncCallFuture<R> {
+    pub(crate) fn error(err: Error) -> Self {
+        AsyncCallFuture(Err(err))
+    }
+}
+
+#[cfg(feature = "async")]
+impl<R: FromLuaMulti> Future for AsyncCallFuture<R> {
+    type Output = Result<R>;
+
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        // Safety: We're not moving any pinned data
+        let this = unsafe { self.get_unchecked_mut() };
+        match &mut this.0 {
+            Ok(thread) => {
+                let pinned_thread = unsafe { Pin::new_unchecked(thread) };
+                pinned_thread.poll(cx)
+            }
+            Err(err) => Poll::Ready(Err(err.clone())),
+        }
+    }
+}
+
 #[cfg(test)]
 mod assertions {
     use super::*;
@@ -596,4 +689,7 @@ mod assertions {
     static_assertions::assert_not_impl_any!(Function: Send);
     #[cfg(feature = "send")]
     static_assertions::assert_impl_all!(Function: Send, Sync);
+
+    #[cfg(all(feature = "async", feature = "send"))]
+    static_assertions::assert_impl_all!(AsyncCallFuture<()>: Send);
 }

src/lib.rs

@@ -32,41 +32,32 @@
 //! [`serde::Serialize`] or [`serde::Deserialize`] can be converted.
 //! For convenience, additional functionality to handle `NULL` values and arrays is provided.
 //!
-//! The [`Value`] enum implements [`serde::Serialize`] trait to support serializing Lua values
-//! (including [`UserData`]) into Rust values.
+//! The [`Value`] enum and other types implement [`serde::Serialize`] trait to support serializing
+//! Lua values into Rust values.
 //!
-//! Requires `feature = "serialize"`.
+//! Requires `feature = "serde"`.
 //!
 //! # Async/await support
 //!
-//! The [`create_async_function`] allows creating non-blocking functions that returns [`Future`].
-//! Lua code with async capabilities can be executed by [`call_async`] family of functions or
-//! polling [`AsyncThread`] using any runtime (eg. Tokio).
+//! The [`Lua::create_async_function`] allows creating non-blocking functions that returns
+//! [`Future`]. Lua code with async capabilities can be executed by [`Function::call_async`] family
+//! of functions or polling [`AsyncThread`] using any runtime (eg. Tokio).
 //!
 //! Requires `feature = "async"`.
 //!
-//! # `Send` requirement
+//! # `Send` and `Sync` support
+//!
 //! By default `mlua` is `!Send`. This can be changed by enabling `feature = "send"` that adds
-//! `Send` requirement to [`Function`]s and [`UserData`].
+//! `Send` requirement to Rust functions and [`UserData`] types.
+//!
+//! In this case [`Lua`] object and their types can be send or used from other threads. Internally
+//! access to Lua VM is synchronized using a reentrant mutex that can be locked many times within
+//! the same thread.
 //!
 //! [Lua programming language]: https://www.lua.org/
-//! [`Lua`]: crate::Lua
 //! [executing]: crate::Chunk::exec
 //! [evaluating]: crate::Chunk::eval
 //! [globals]: crate::Lua::globals
-//! [`IntoLua`]: crate::IntoLua
-//! [`FromLua`]: crate::FromLua
-//! [`IntoLuaMulti`]: crate::IntoLuaMulti
-//! [`FromLuaMulti`]: crate::FromLuaMulti
-//! [`Function`]: crate::Function
-//! [`UserData`]: crate::UserData
-//! [`UserDataFields`]: crate::UserDataFields
-//! [`UserDataMethods`]: crate::UserDataMethods
-//! [`LuaSerdeExt`]: crate::LuaSerdeExt
-//! [`Value`]: crate::Value
-//! [`create_async_function`]: crate::Lua::create_async_function
-//! [`call_async`]: crate::Function::call_async
-//! [`AsyncThread`]: crate::AsyncThread
 //! [`Future`]: std::future::Future
 //! [`serde::Serialize`]: https://docs.serde.rs/serde/ser/trait.Serialize.html
 //! [`serde::Deserialize`]: https://docs.serde.rs/serde/de/trait.Deserialize.html
@@ -74,20 +65,24 @@
 // Deny warnings inside doc tests / examples. When this isn't present, rustdoc doesn't show *any*
 // warnings at all.
 #![cfg_attr(docsrs, feature(doc_cfg))]
+#![cfg_attr(not(send), allow(clippy::arc_with_non_send_sync))]
+#![allow(clippy::ptr_eq)]
+#![allow(unsafe_op_in_unsafe_fn)]
 
 #[macro_use]
 mod macros;
 
+mod buffer;
 mod chunk;
 mod conversion;
+mod debug;
 mod error;
 mod function;
-mod hook;
-#[cfg(feature = "luau")]
+#[cfg(any(feature = "luau", doc))]
 mod luau;
 mod memory;
 mod multi;
-// mod scope;
+mod scope;
 mod state;
 mod stdlib;
 mod string;
@@ -98,6 +93,7 @@ mod types;
 mod userdata;
 mod util;
 mod value;
+mod vector;
 
 pub mod prelude;
 
@@ -105,44 +101,51 @@ pub use bstr::BString;
 pub use ffi::{self, lua_CFunction, lua_State};
 
 pub use crate::chunk::{AsChunk, Chunk, ChunkMode};
+pub use crate::debug::{Debug, DebugEvent, DebugNames, DebugSource, DebugStack};
 pub use crate::error::{Error, ErrorContext, ExternalError, ExternalResult, Result};
 pub use crate::function::{Function, FunctionInfo};
-pub use crate::hook::{Debug, DebugEvent, DebugNames, DebugSource, DebugStack};
-pub use crate::multi::Variadic;
-pub use crate::state::{GCMode, Lua, LuaOptions};
-// pub use crate::scope::Scope;
+pub use crate::multi::{MultiValue, Variadic};
+pub use crate::scope::Scope;
+pub use crate::state::{GCMode, Lua, LuaOptions, WeakLua};
 pub use crate::stdlib::StdLib;
 pub use crate::string::{BorrowedBytes, BorrowedStr, String};
 pub use crate::table::{Table, TablePairs, TableSequence};
 pub use crate::thread::{Thread, ThreadStatus};
-pub use crate::traits::ObjectLike;
-pub use crate::types::{AppDataRef, AppDataRefMut, Integer, LightUserData, MaybeSend, Number, RegistryKey};
+pub use crate::traits::{
+    FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, LuaNativeFn, LuaNativeFnMut, ObjectLike,
+};
+pub use crate::types::{
+    AppDataRef, AppDataRefMut, Either, Integer, LightUserData, MaybeSend, Number, RegistryKey, VmState,
+};
 pub use crate::userdata::{
     AnyUserData, MetaMethod, UserData, UserDataFields, UserDataMetatable, UserDataMethods, UserDataRef,
     UserDataRefMut, UserDataRegistry,
 };
-pub use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, MultiValue, Nil, Value};
+pub use crate::value::{Nil, Value};
 
 #[cfg(not(feature = "luau"))]
-pub use crate::hook::HookTriggers;
+pub use crate::debug::HookTriggers;
 
 #[cfg(any(feature = "luau", doc))]
 #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
 pub use crate::{
-    chunk::Compiler,
+    buffer::Buffer,
+    chunk::{CompileConstant, Compiler},
     function::CoverageInfo,
-    types::{Vector, VmState},
+    luau::{NavigateError, Require, TextRequirer},
+    vector::Vector,
 };
 
 #[cfg(feature = "async")]
-pub use crate::thread::AsyncThread;
+#[cfg_attr(docsrs, doc(cfg(feature = "async")))]
+pub use crate::{thread::AsyncThread, traits::LuaNativeAsyncFn};
 
-#[cfg(feature = "serialize")]
+#[cfg(feature = "serde")]
 #[doc(inline)]
 pub use crate::serde::{de::Options as DeserializeOptions, ser::Options as SerializeOptions, LuaSerdeExt};
 
-#[cfg(feature = "serialize")]
-#[cfg_attr(docsrs, doc(cfg(feature = "serialize")))]
+#[cfg(feature = "serde")]
+#[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
 pub mod serde;
 
 #[cfg(feature = "mlua_derive")]
@@ -198,10 +201,6 @@ extern crate mlua_derive;
 /// - The `//` (floor division) operator is unusable, as its start a comment.
 ///
 /// Everything else should work.
-///
-/// [`AsChunk`]: crate::AsChunk
-/// [`UserData`]: crate::UserData
-/// [`IntoLua`]: crate::IntoLua
 #[cfg(feature = "macros")]
 #[cfg_attr(docsrs, doc(cfg(feature = "macros")))]
 pub use mlua_derive::chunk;
@@ -218,7 +217,7 @@ pub use mlua_derive::FromLua;
 ///
 /// You can register multiple entrypoints as required.
 ///
-/// ```
+/// ```ignore
 /// use mlua::{Lua, Result, Table};
 ///
 /// #[mlua::lua_module]
@@ -255,7 +254,7 @@ pub use mlua_derive::FromLua;
 ///     ...
 /// }
 /// ```
-#[cfg(any(feature = "module", docsrs))]
+#[cfg(all(feature = "mlua_derive", any(feature = "module", doc)))]
 #[cfg_attr(docsrs, doc(cfg(feature = "module")))]
 pub use mlua_derive::lua_module;
 

src/luau/mod.rs

@@ -1,17 +1,32 @@
 use std::ffi::CStr;
-use std::os::raw::{c_float, c_int};
+use std::os::raw::c_int;
+use std::ptr;
 
+use crate::chunk::ChunkMode;
 use crate::error::Result;
-use crate::state::Lua;
+use crate::function::Function;
+use crate::state::{callback_error_ext, ExtraData, Lua};
+use crate::traits::{FromLuaMulti, IntoLua};
+use crate::types::MaybeSend;
+
+pub use require::{NavigateError, Require, TextRequirer};
 
 // Since Luau has some missing standard functions, we re-implement them here
 
 impl Lua {
+    /// Create a custom Luau `require` function using provided [`Require`] implementation to find
+    /// and load modules.
+    #[cfg(any(feature = "luau", doc))]
+    #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
+    pub fn create_require_function<R: Require + MaybeSend + 'static>(&self, require: R) -> Result<Function> {
+        require::create_require_function(self, require)
+    }
+
     pub(crate) unsafe fn configure_luau(&self) -> Result<()> {
         let globals = self.globals();
 
         globals.raw_set("collectgarbage", self.create_c_function(lua_collectgarbage)?)?;
-        globals.raw_set("vector", self.create_c_function(lua_vector)?)?;
+        globals.raw_set("loadstring", self.create_c_function(lua_loadstring)?)?;
 
         // Set `_VERSION` global to include version number
         // The environment variable `LUAU_VERSION` set by the build script
@@ -19,11 +34,10 @@ impl Lua {
             globals.raw_set("_VERSION", format!("Luau {version}"))?;
         }
 
-        Ok(())
-    }
+        // Enable default `require` implementation
+        let require = self.create_require_function(require::TextRequirer::new())?;
+        self.globals().raw_set("require", require)?;
 
-    pub(crate) fn disable_c_modules(&self) -> Result<()> {
-        package::disable_dylibs(self);
         Ok(())
     }
 }
@@ -32,16 +46,17 @@ unsafe extern "C-unwind" fn lua_collectgarbage(state: *mut ffi::lua_State) -> c_
     let option = ffi::luaL_optstring(state, 1, cstr!("collect"));
     let option = CStr::from_ptr(option);
     let arg = ffi::luaL_optinteger(state, 2, 0);
+    let is_sandboxed = (*ExtraData::get(state)).sandboxed;
     match option.to_str() {
-        Ok("collect") => {
+        Ok("collect") if !is_sandboxed => {
             ffi::lua_gc(state, ffi::LUA_GCCOLLECT, 0);
             0
         }
-        Ok("stop") => {
+        Ok("stop") if !is_sandboxed => {
             ffi::lua_gc(state, ffi::LUA_GCSTOP, 0);
             0
         }
-        Ok("restart") => {
+        Ok("restart") if !is_sandboxed => {
             ffi::lua_gc(state, ffi::LUA_GCRESTART, 0);
             0
         }
@@ -51,12 +66,12 @@ unsafe extern "C-unwind" fn lua_collectgarbage(state: *mut ffi::lua_State) -> c_
             ffi::lua_pushnumber(state, kbytes + kbytes_rem / 1024.0);
             1
         }
-        Ok("step") => {
-            let res = ffi::lua_gc(state, ffi::LUA_GCSTEP, arg);
+        Ok("step") if !is_sandboxed => {
+            let res = ffi::lua_gc(state, ffi::LUA_GCSTEP, arg as _);
             ffi::lua_pushboolean(state, res);
             1
         }
-        Ok("isrunning") => {
+        Ok("isrunning") if !is_sandboxed => {
             let res = ffi::lua_gc(state, ffi::LUA_GCISRUNNING, 0);
             ffi::lua_pushboolean(state, res);
             1
@@ -65,21 +80,20 @@ unsafe extern "C-unwind" fn lua_collectgarbage(state: *mut ffi::lua_State) -> c_
     }
 }
 
-// Luau vector datatype constructor
-unsafe extern "C-unwind" fn lua_vector(state: *mut ffi::lua_State) -> c_int {
-    let x = ffi::luaL_checknumber(state, 1) as c_float;
-    let y = ffi::luaL_checknumber(state, 2) as c_float;
-    let z = ffi::luaL_checknumber(state, 3) as c_float;
-    #[cfg(feature = "luau-vector4")]
-    let w = ffi::luaL_checknumber(state, 4) as c_float;
-
-    #[cfg(not(feature = "luau-vector4"))]
-    ffi::lua_pushvector(state, x, y, z);
-    #[cfg(feature = "luau-vector4")]
-    ffi::lua_pushvector(state, x, y, z, w);
-    1
+unsafe extern "C-unwind" fn lua_loadstring(state: *mut ffi::lua_State) -> c_int {
+    callback_error_ext(state, ptr::null_mut(), false, move |extra, nargs| {
+        let rawlua = (*extra).raw_lua();
+        let (chunk, chunk_name) =
+            <(String, Option<String>)>::from_stack_args(nargs, 1, Some("loadstring"), rawlua)?;
+        let chunk_name = chunk_name.as_deref().unwrap_or("=(loadstring)");
+        (rawlua.lua())
+            .load(chunk)
+            .set_name(chunk_name)
+            .set_mode(ChunkMode::Text)
+            .into_function()?
+            .push_into_stack(rawlua)?;
+        Ok(1)
+    })
 }
 
-pub(crate) use package::register_package_module;
-
-mod package;
+mod require;

src/luau/package.rs

@@ -1,270 +0,0 @@
-use std::ffi::CStr;
-use std::fmt::Write;
-use std::os::raw::c_int;
-use std::path::{PathBuf, MAIN_SEPARATOR_STR};
-use std::string::String as StdString;
-use std::{env, fs};
-
-use crate::chunk::ChunkMode;
-use crate::error::Result;
-use crate::state::Lua;
-use crate::table::Table;
-use crate::value::{IntoLua, Value};
-
-#[cfg(unix)]
-use {libloading::Library, rustc_hash::FxHashMap};
-
-//
-// Luau package module
-//
-
-#[cfg(unix)]
-const TARGET_MLUA_LUAU_ABI_VERSION: u32 = 1;
-
-#[cfg(all(unix, feature = "module"))]
-#[no_mangle]
-#[used]
-pub static MLUA_LUAU_ABI_VERSION: u32 = TARGET_MLUA_LUAU_ABI_VERSION;
-
-// We keep reference to the loaded dylibs in application data
-#[cfg(unix)]
-struct LoadedDylibs(FxHashMap<PathBuf, Library>);
-
-#[cfg(unix)]
-impl std::ops::Deref for LoadedDylibs {
-    type Target = FxHashMap<PathBuf, Library>;
-
-    fn deref(&self) -> &Self::Target {
-        &self.0
-    }
-}
-
-#[cfg(unix)]
-impl std::ops::DerefMut for LoadedDylibs {
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        &mut self.0
-    }
-}
-
-pub(crate) fn register_package_module(lua: &Lua) -> Result<()> {
-    // Create the package table
-    let package = lua.create_table()?;
-
-    // Set `package.path`
-    let mut search_path = env::var("LUAU_PATH")
-        .or_else(|_| env::var("LUA_PATH"))
-        .unwrap_or_default();
-    if search_path.is_empty() {
-        search_path = "?.luau;?.lua".to_string();
-    }
-    package.raw_set("path", search_path)?;
-
-    // Set `package.cpath`
-    #[cfg(unix)]
-    {
-        let mut search_cpath = env::var("LUAU_CPATH")
-            .or_else(|_| env::var("LUA_CPATH"))
-            .unwrap_or_default();
-        if search_cpath.is_empty() {
-            if cfg!(any(target_os = "macos", target_os = "ios")) {
-                search_cpath = "?.dylib".to_string();
-            } else {
-                search_cpath = "?.so".to_string();
-            }
-        }
-        package.raw_set("cpath", search_cpath)?;
-    }
-
-    // Set `package.loaded` (table with a list of loaded modules)
-    let loaded = if let Ok(Some(loaded)) = lua.named_registry_value::<Option<Table>>("_LOADED") {
-        package.raw_set("loaded", &loaded)?;
-        loaded
-    } else {
-        let loaded = lua.create_table()?;
-        package.raw_set("loaded", &loaded)?;
-        lua.set_named_registry_value("_LOADED", &loaded)?;
-        loaded
-    };
-
-    // Set `package.loaders`
-    let loaders = lua.create_sequence_from([lua.create_function(lua_loader)?])?;
-    package.raw_set("loaders", &loaders)?;
-    #[cfg(unix)]
-    {
-        loaders.push(lua.create_function(dylib_loader)?)?;
-        lua.set_app_data(LoadedDylibs(FxHashMap::default()));
-    }
-    lua.set_named_registry_value("_LOADERS", loaders)?;
-
-    // Register the module and `require` function in globals
-    let globals = lua.globals();
-    globals.raw_set("package", &package)?;
-    loaded.raw_set("package", package)?;
-    globals.raw_set("require", unsafe { lua.create_c_function(lua_require)? })?;
-
-    Ok(())
-}
-
-#[allow(unused_variables)]
-pub(crate) fn disable_dylibs(lua: &Lua) {
-    // Presence of `LoadedDylibs` in app data is used as a flag
-    // to check whether binary modules are enabled
-    #[cfg(unix)]
-    lua.remove_app_data::<LoadedDylibs>();
-}
-
-unsafe extern "C-unwind" fn lua_require(state: *mut ffi::lua_State) -> c_int {
-    ffi::lua_settop(state, 1);
-    let name = ffi::luaL_checkstring(state, 1);
-    ffi::luaL_getsubtable(state, ffi::LUA_REGISTRYINDEX, cstr!("_LOADED")); // _LOADED is at index 2
-    if ffi::lua_rawgetfield(state, 2, name) != ffi::LUA_TNIL {
-        return 1; // module is already loaded
-    }
-    ffi::lua_pop(state, 1); // remove nil
-
-    // load the module
-    let err_buf = ffi::lua_newuserdata_t::<StdString>(state);
-    err_buf.write(StdString::new());
-    ffi::luaL_getsubtable(state, ffi::LUA_REGISTRYINDEX, cstr!("_LOADERS")); // _LOADERS is at index 3
-    for i in 1.. {
-        if ffi::lua_rawgeti(state, -1, i) == ffi::LUA_TNIL {
-            // no more loaders?
-            if (*err_buf).is_empty() {
-                ffi::luaL_error(state, cstr!("module '%s' not found"), name);
-            } else {
-                let bytes = (*err_buf).as_bytes();
-                let extra = ffi::lua_pushlstring(state, bytes.as_ptr() as *const _, bytes.len());
-                ffi::luaL_error(state, cstr!("module '%s' not found:%s"), name, extra);
-            }
-        }
-        ffi::lua_pushvalue(state, 1); // name arg
-        ffi::lua_call(state, 1, 2); // call loader
-        match ffi::lua_type(state, -2) {
-            ffi::LUA_TFUNCTION => break, // loader found
-            ffi::LUA_TSTRING => {
-                // error message
-                let msg = ffi::lua_tostring(state, -2);
-                let msg = CStr::from_ptr(msg).to_string_lossy();
-                _ = write!(&mut *err_buf, "\n\t{msg}");
-            }
-            _ => {}
-        }
-        ffi::lua_pop(state, 2); // remove both results
-    }
-    ffi::lua_pushvalue(state, 1); // name is 1st argument to module loader
-    ffi::lua_rotate(state, -2, 1); // loader data <-> name
-
-    // stack: ...; loader function; module name; loader data
-    ffi::lua_call(state, 2, 1);
-    // stack: ...; result from loader function
-    if ffi::lua_isnil(state, -1) != 0 {
-        ffi::lua_pop(state, 1);
-        ffi::lua_pushboolean(state, 1); // use true as result
-    }
-    ffi::lua_pushvalue(state, -1); // make copy of entrypoint result
-    ffi::lua_setfield(state, 2, name); /* _LOADED[name] = returned value */
-    1
-}
-
-/// Searches for the given `name` in the given `path`.
-///
-/// `path` is a string containing a sequence of templates separated by semicolons.
-fn package_searchpath(name: &str, search_path: &str, try_prefix: bool) -> Option<PathBuf> {
-    let mut names = vec![name.replace('.', MAIN_SEPARATOR_STR)];
-    if try_prefix && name.contains('.') {
-        let prefix = name.split_once('.').map(|(prefix, _)| prefix).unwrap();
-        names.push(prefix.to_string());
-    }
-    for path in search_path.split(';') {
-        for name in &names {
-            let file_path = PathBuf::from(path.replace('?', name));
-            if let Ok(true) = fs::metadata(&file_path).map(|m| m.is_file()) {
-                return Some(file_path);
-            }
-        }
-    }
-    None
-}
-
-//
-// Module loaders
-//
-
-/// Tries to load a lua (text) file
-fn lua_loader(lua: &Lua, modname: StdString) -> Result<Value> {
-    let package = {
-        let loaded = lua.named_registry_value::<Table>("_LOADED")?;
-        loaded.raw_get::<Table>("package")
-    }?;
-    let search_path = package.get::<StdString>("path").unwrap_or_default();
-
-    if let Some(file_path) = package_searchpath(&modname, &search_path, false) {
-        match fs::read(&file_path) {
-            Ok(buf) => {
-                return lua
-                    .load(&buf)
-                    .set_name(format!("={}", file_path.display()))
-                    .set_mode(ChunkMode::Text)
-                    .into_function()
-                    .map(Value::Function);
-            }
-            Err(err) => {
-                return format!("cannot open '{}': {err}", file_path.display()).into_lua(lua);
-            }
-        }
-    }
-
-    Ok(Value::Nil)
-}
-
-/// Tries to load a dynamic library
-#[cfg(unix)]
-fn dylib_loader(lua: &Lua, modname: StdString) -> Result<Value> {
-    let package = {
-        let loaded = lua.named_registry_value::<Table>("_LOADED")?;
-        loaded.raw_get::<Table>("package")
-    }?;
-    let search_cpath = package.get::<StdString>("cpath").unwrap_or_default();
-
-    let find_symbol = |lib: &Library| unsafe {
-        if let Ok(entry) = lib.get::<ffi::lua_CFunction>(format!("luaopen_{modname}\0").as_bytes()) {
-            return lua.create_c_function(*entry).map(Value::Function);
-        }
-        // Try all in one mode
-        if let Ok(entry) =
-            lib.get::<ffi::lua_CFunction>(format!("luaopen_{}\0", modname.replace('.', "_")).as_bytes())
-        {
-            return lua.create_c_function(*entry).map(Value::Function);
-        }
-        "cannot find module entrypoint".into_lua(lua)
-    };
-
-    if let Some(file_path) = package_searchpath(&modname, &search_cpath, true) {
-        let file_path = file_path.canonicalize()?;
-        // Load the library and check for symbol
-        unsafe {
-            let mut loaded_dylibs = match lua.app_data_mut::<LoadedDylibs>() {
-                Some(loaded_dylibs) => loaded_dylibs,
-                None => return "dynamic libraries are disabled in safe mode".into_lua(lua),
-            };
-            // Check if it's already loaded
-            if let Some(lib) = loaded_dylibs.get(&file_path) {
-                return find_symbol(lib);
-            }
-            if let Ok(lib) = Library::new(&file_path) {
-                // Check version
-                let mod_version = lib.get::<*const u32>(b"MLUA_LUAU_ABI_VERSION");
-                let mod_version = mod_version.map(|v| **v).unwrap_or_default();
-                if mod_version != TARGET_MLUA_LUAU_ABI_VERSION {
-                    let err = format!("wrong module ABI version (expected {TARGET_MLUA_LUAU_ABI_VERSION}, got {mod_version})");
-                    return err.into_lua(lua);
-                }
-                let symbol = find_symbol(&lib);
-                loaded_dylibs.insert(file_path, lib);
-                return symbol;
-            }
-        }
-    }
-
-    Ok(Value::Nil)
-}

src/luau/require.rs

@@ -0,0 +1,671 @@
+use std::cell::RefCell;
+use std::collections::VecDeque;
+use std::ffi::CStr;
+use std::io::Result as IoResult;
+use std::ops::{Deref, DerefMut};
+use std::os::raw::{c_char, c_int, c_void};
+use std::path::{Component, Path, PathBuf};
+use std::result::Result as StdResult;
+use std::{env, fmt, fs, mem, ptr};
+
+use crate::error::{Error, Result};
+use crate::function::Function;
+use crate::state::{callback_error_ext, Lua};
+use crate::table::Table;
+use crate::types::MaybeSend;
+
+/// An error that can occur during navigation in the Luau `require-by-string` system.
+#[cfg(any(feature = "luau", doc))]
+#[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
+#[derive(Debug, Clone)]
+pub enum NavigateError {
+    Ambiguous,
+    NotFound,
+    Other(Error),
+}
+
+#[cfg(feature = "luau")]
+trait IntoNavigateResult {
+    fn into_nav_result(self) -> Result<ffi::luarequire_NavigateResult>;
+}
+
+#[cfg(feature = "luau")]
+impl IntoNavigateResult for StdResult<(), NavigateError> {
+    fn into_nav_result(self) -> Result<ffi::luarequire_NavigateResult> {
+        match self {
+            Ok(()) => Ok(ffi::luarequire_NavigateResult::Success),
+            Err(NavigateError::Ambiguous) => Ok(ffi::luarequire_NavigateResult::Ambiguous),
+            Err(NavigateError::NotFound) => Ok(ffi::luarequire_NavigateResult::NotFound),
+            Err(NavigateError::Other(err)) => Err(err),
+        }
+    }
+}
+
+impl From<Error> for NavigateError {
+    fn from(err: Error) -> Self {
+        NavigateError::Other(err)
+    }
+}
+
+#[cfg(feature = "luau")]
+type WriteResult = ffi::luarequire_WriteResult;
+
+/// A trait for handling modules loading and navigation in the Luau `require-by-string` system.
+#[cfg(any(feature = "luau", doc))]
+#[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
+pub trait Require {
+    /// Returns `true` if "require" is permitted for the given chunk name.
+    fn is_require_allowed(&self, chunk_name: &str) -> bool;
+
+    /// Resets the internal state to point at the requirer module.
+    fn reset(&mut self, chunk_name: &str) -> StdResult<(), NavigateError>;
+
+    /// Resets the internal state to point at an aliased module.
+    ///
+    /// This function received an exact path from a configuration file.
+    /// It's only called when an alias's path cannot be resolved relative to its
+    /// configuration file.
+    fn jump_to_alias(&mut self, path: &str) -> StdResult<(), NavigateError>;
+
+    // Navigate to parent directory
+    fn to_parent(&mut self) -> StdResult<(), NavigateError>;
+
+    /// Navigate to the given child directory.
+    fn to_child(&mut self, name: &str) -> StdResult<(), NavigateError>;
+
+    /// Returns whether the context is currently pointing at a module
+    fn has_module(&self) -> bool;
+
+    /// Provides a cache key representing the current module.
+    ///
+    /// This function is only called if `has_module` returns true.
+    fn cache_key(&self) -> String;
+
+    /// Returns whether a configuration is present in the current context.
+    fn has_config(&self) -> bool;
+
+    /// Returns the contents of the configuration file in the current context.
+    ///
+    /// This function is only called if `has_config` returns true.
+    fn config(&self) -> IoResult<Vec<u8>>;
+
+    /// Returns a loader function for the current module, that when called, loads the module
+    /// and returns the result.
+    ///
+    /// Loader can be sync or async.
+    /// This function is only called if `has_module` returns true.
+    fn loader(&self, lua: &Lua) -> Result<Function>;
+}
+
+impl fmt::Debug for dyn Require {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "<dyn Require>")
+    }
+}
+
+/// The standard implementation of Luau `require-by-string` navigation.
+#[derive(Default, Debug)]
+pub struct TextRequirer {
+    /// An absolute path to the current Luau module (not mapped to a physical file)
+    abs_path: PathBuf,
+    /// A relative path to the current Luau module (not mapped to a physical file)
+    rel_path: PathBuf,
+    /// A physical path to the current Luau module, which is a file or a directory with an
+    /// `init.lua(u)` file
+    resolved_path: Option<PathBuf>,
+}
+
+impl TextRequirer {
+    /// The prefix used for chunk names in the require system.
+    /// Only chunk names starting with this prefix are allowed to be used in `require`.
+    const CHUNK_PREFIX: &str = "@";
+
+    /// The file extensions that are considered valid for Luau modules.
+    const FILE_EXTENSIONS: &[&str] = &["luau", "lua"];
+
+    /// Creates a new `TextRequirer` instance.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    fn normalize_chunk_name(chunk_name: &str) -> &str {
+        if let Some((path, line)) = chunk_name.split_once(':') {
+            if line.parse::<u32>().is_ok() {
+                return path;
+            }
+        }
+        chunk_name
+    }
+
+    // Normalizes the path by removing unnecessary components
+    fn normalize_path(path: &Path) -> PathBuf {
+        let mut components = VecDeque::new();
+
+        for comp in path.components() {
+            match comp {
+                Component::Prefix(..) | Component::RootDir => {
+                    components.push_back(comp);
+                }
+                Component::CurDir => {}
+                Component::ParentDir => {
+                    if matches!(components.back(), None | Some(Component::ParentDir)) {
+                        components.push_back(Component::ParentDir);
+                    } else if matches!(components.back(), Some(Component::Normal(..))) {
+                        components.pop_back();
+                    }
+                }
+                Component::Normal(..) => components.push_back(comp),
+            }
+        }
+
+        if matches!(components.front(), None | Some(Component::Normal(..))) {
+            components.push_front(Component::CurDir);
+        }
+
+        // Join the components back together
+        components.into_iter().collect()
+    }
+
+    /// Resolve a Luau module path to a physical file or directory.
+    ///
+    /// Empty directories without init files are considered valid as "intermediate" directories.
+    fn resolve_module(path: &Path) -> StdResult<Option<PathBuf>, NavigateError> {
+        let mut found_path = None;
+
+        if path.components().next_back() != Some(Component::Normal("init".as_ref())) {
+            let current_ext = (path.extension().and_then(|s| s.to_str()))
+                .map(|s| format!("{s}."))
+                .unwrap_or_default();
+            for ext in Self::FILE_EXTENSIONS {
+                let candidate = path.with_extension(format!("{current_ext}{ext}"));
+                if candidate.is_file() && found_path.replace(candidate).is_some() {
+                    return Err(NavigateError::Ambiguous);
+                }
+            }
+        }
+        if path.is_dir() {
+            for component in Self::FILE_EXTENSIONS.iter().map(|ext| format!("init.{ext}")) {
+                let candidate = path.join(component);
+                if candidate.is_file() && found_path.replace(candidate).is_some() {
+                    return Err(NavigateError::Ambiguous);
+                }
+            }
+
+            if found_path.is_none() {
+                // Directories without init files are considered valid "intermediate" path
+                return Ok(None);
+            }
+        }
+
+        Ok(Some(found_path.ok_or(NavigateError::NotFound)?))
+    }
+}
+
+impl Require for TextRequirer {
+    fn is_require_allowed(&self, chunk_name: &str) -> bool {
+        chunk_name.starts_with(Self::CHUNK_PREFIX)
+    }
+
+    fn reset(&mut self, chunk_name: &str) -> StdResult<(), NavigateError> {
+        if !chunk_name.starts_with(Self::CHUNK_PREFIX) {
+            return Err(NavigateError::NotFound);
+        }
+        let chunk_name = Self::normalize_chunk_name(&chunk_name[1..]);
+        let chunk_path = Self::normalize_path(chunk_name.as_ref());
+
+        if chunk_path.extension() == Some("rs".as_ref()) {
+            // Special case for Rust source files, reset to the current directory
+            let chunk_filename = chunk_path.file_name().unwrap();
+            let cwd = env::current_dir().map_err(|_| NavigateError::NotFound)?;
+            self.abs_path = Self::normalize_path(&cwd.join(chunk_filename));
+            self.rel_path = ([Component::CurDir, Component::Normal(chunk_filename)].into_iter()).collect();
+            self.resolved_path = None;
+
+            return Ok(());
+        }
+
+        if chunk_path.is_absolute() {
+            let resolved_path = Self::resolve_module(&chunk_path)?;
+            self.abs_path = chunk_path.clone();
+            self.rel_path = chunk_path;
+            self.resolved_path = resolved_path;
+        } else {
+            // Relative path
+            let cwd = env::current_dir().map_err(|_| NavigateError::NotFound)?;
+            let abs_path = Self::normalize_path(&cwd.join(&chunk_path));
+            let resolved_path = Self::resolve_module(&abs_path)?;
+            self.abs_path = abs_path;
+            self.rel_path = chunk_path;
+            self.resolved_path = resolved_path;
+        }
+
+        Ok(())
+    }
+
+    fn jump_to_alias(&mut self, path: &str) -> StdResult<(), NavigateError> {
+        let path = Self::normalize_path(path.as_ref());
+        let resolved_path = Self::resolve_module(&path)?;
+
+        self.abs_path = path.clone();
+        self.rel_path = path;
+        self.resolved_path = resolved_path;
+
+        Ok(())
+    }
+
+    fn to_parent(&mut self) -> StdResult<(), NavigateError> {
+        let mut abs_path = self.abs_path.clone();
+        if !abs_path.pop() {
+            // It's important to return `NotFound` if we reached the root, as it's a "recoverable" error if we
+            // cannot go beyond the root directory.
+            // Luau "require-by-string` has a special logic to search for config file to resolve aliases.
+            return Err(NavigateError::NotFound);
+        }
+        let mut rel_parent = self.rel_path.clone();
+        rel_parent.pop();
+        let resolved_path = Self::resolve_module(&abs_path)?;
+
+        self.abs_path = abs_path;
+        self.rel_path = Self::normalize_path(&rel_parent);
+        self.resolved_path = resolved_path;
+
+        Ok(())
+    }
+
+    fn to_child(&mut self, name: &str) -> StdResult<(), NavigateError> {
+        let abs_path = self.abs_path.join(name);
+        let rel_path = self.rel_path.join(name);
+        let resolved_path = Self::resolve_module(&abs_path)?;
+
+        self.abs_path = abs_path;
+        self.rel_path = rel_path;
+        self.resolved_path = resolved_path;
+
+        Ok(())
+    }
+
+    fn has_module(&self) -> bool {
+        (self.resolved_path.as_deref())
+            .map(Path::is_file)
+            .unwrap_or(false)
+    }
+
+    fn cache_key(&self) -> String {
+        self.resolved_path.as_deref().unwrap().display().to_string()
+    }
+
+    fn has_config(&self) -> bool {
+        self.abs_path.is_dir() && self.abs_path.join(".luaurc").is_file()
+    }
+
+    fn config(&self) -> IoResult<Vec<u8>> {
+        fs::read(self.abs_path.join(".luaurc"))
+    }
+
+    fn loader(&self, lua: &Lua) -> Result<Function> {
+        let name = format!("@{}", self.rel_path.display());
+        lua.load(self.resolved_path.as_deref().unwrap())
+            .set_name(name)
+            .into_function()
+    }
+}
+
+struct Context(Box<dyn Require>);
+
+impl Deref for Context {
+    type Target = dyn Require;
+
+    fn deref(&self) -> &Self::Target {
+        &*self.0
+    }
+}
+
+impl DerefMut for Context {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut *self.0
+    }
+}
+
+macro_rules! try_borrow {
+    ($state:expr, $ctx:expr) => {
+        match (*($ctx as *const RefCell<Context>)).try_borrow() {
+            Ok(ctx) => ctx,
+            Err(_) => ffi::luaL_error($state, cstr!("require context is already borrowed")),
+        }
+    };
+}
+
+macro_rules! try_borrow_mut {
+    ($state:expr, $ctx:expr) => {
+        match (*($ctx as *const RefCell<Context>)).try_borrow_mut() {
+            Ok(ctx) => ctx,
+            Err(_) => ffi::luaL_error($state, cstr!("require context is already borrowed")),
+        }
+    };
+}
+
+#[cfg(feature = "luau")]
+pub(super) unsafe extern "C-unwind" fn init_config(config: *mut ffi::luarequire_Configuration) {
+    if config.is_null() {
+        return;
+    }
+
+    unsafe extern "C-unwind" fn is_require_allowed(
+        state: *mut ffi::lua_State,
+        ctx: *mut c_void,
+        requirer_chunkname: *const c_char,
+    ) -> bool {
+        if requirer_chunkname.is_null() {
+            return false;
+        }
+
+        let this = try_borrow!(state, ctx);
+        let chunk_name = CStr::from_ptr(requirer_chunkname).to_string_lossy();
+        this.is_require_allowed(&chunk_name)
+    }
+
+    unsafe extern "C-unwind" fn reset(
+        state: *mut ffi::lua_State,
+        ctx: *mut c_void,
+        requirer_chunkname: *const c_char,
+    ) -> ffi::luarequire_NavigateResult {
+        let mut this = try_borrow_mut!(state, ctx);
+        let chunk_name = CStr::from_ptr(requirer_chunkname).to_string_lossy();
+        callback_error_ext(state, ptr::null_mut(), true, move |_, _| {
+            this.reset(&chunk_name).into_nav_result()
+        })
+    }
+
+    unsafe extern "C-unwind" fn jump_to_alias(
+        state: *mut ffi::lua_State,
+        ctx: *mut c_void,
+        path: *const c_char,
+    ) -> ffi::luarequire_NavigateResult {
+        let mut this = try_borrow_mut!(state, ctx);
+        let path = CStr::from_ptr(path).to_string_lossy();
+        callback_error_ext(state, ptr::null_mut(), true, move |_, _| {
+            this.jump_to_alias(&path).into_nav_result()
+        })
+    }
+
+    unsafe extern "C-unwind" fn to_parent(
+        state: *mut ffi::lua_State,
+        ctx: *mut c_void,
+    ) -> ffi::luarequire_NavigateResult {
+        let mut this = try_borrow_mut!(state, ctx);
+        callback_error_ext(state, ptr::null_mut(), true, move |_, _| {
+            this.to_parent().into_nav_result()
+        })
+    }
+
+    unsafe extern "C-unwind" fn to_child(
+        state: *mut ffi::lua_State,
+        ctx: *mut c_void,
+        name: *const c_char,
+    ) -> ffi::luarequire_NavigateResult {
+        let mut this = try_borrow_mut!(state, ctx);
+        let name = CStr::from_ptr(name).to_string_lossy();
+        callback_error_ext(state, ptr::null_mut(), true, move |_, _| {
+            this.to_child(&name).into_nav_result()
+        })
+    }
+
+    unsafe extern "C-unwind" fn is_module_present(state: *mut ffi::lua_State, ctx: *mut c_void) -> bool {
+        let this = try_borrow!(state, ctx);
+        this.has_module()
+    }
+
+    unsafe extern "C-unwind" fn get_chunkname(
+        _state: *mut ffi::lua_State,
+        _ctx: *mut c_void,
+        buffer: *mut c_char,
+        buffer_size: usize,
+        size_out: *mut usize,
+    ) -> WriteResult {
+        write_to_buffer(buffer, buffer_size, size_out, &[])
+    }
+
+    unsafe extern "C-unwind" fn get_loadname(
+        _state: *mut ffi::lua_State,
+        _ctx: *mut c_void,
+        buffer: *mut c_char,
+        buffer_size: usize,
+        size_out: *mut usize,
+    ) -> WriteResult {
+        write_to_buffer(buffer, buffer_size, size_out, &[])
+    }
+
+    unsafe extern "C-unwind" fn get_cache_key(
+        state: *mut ffi::lua_State,
+        ctx: *mut c_void,
+        buffer: *mut c_char,
+        buffer_size: usize,
+        size_out: *mut usize,
+    ) -> WriteResult {
+        let this = try_borrow!(state, ctx);
+        let cache_key = this.cache_key();
+        write_to_buffer(buffer, buffer_size, size_out, cache_key.as_bytes())
+    }
+
+    unsafe extern "C-unwind" fn is_config_present(state: *mut ffi::lua_State, ctx: *mut c_void) -> bool {
+        let this = try_borrow!(state, ctx);
+        this.has_config()
+    }
+
+    unsafe extern "C-unwind" fn get_config(
+        state: *mut ffi::lua_State,
+        ctx: *mut c_void,
+        buffer: *mut c_char,
+        buffer_size: usize,
+        size_out: *mut usize,
+    ) -> WriteResult {
+        let this = try_borrow!(state, ctx);
+        let config = callback_error_ext(state, ptr::null_mut(), true, move |_, _| Ok(this.config()?));
+        write_to_buffer(buffer, buffer_size, size_out, &config)
+    }
+
+    unsafe extern "C-unwind" fn load(
+        state: *mut ffi::lua_State,
+        ctx: *mut c_void,
+        _path: *const c_char,
+        _chunkname: *const c_char,
+        _loadname: *const c_char,
+    ) -> c_int {
+        let this = try_borrow!(state, ctx);
+        callback_error_ext(state, ptr::null_mut(), true, move |extra, _| {
+            let rawlua = (*extra).raw_lua();
+            let loader = this.loader(rawlua.lua())?;
+            rawlua.push(loader)?;
+            Ok(1)
+        })
+    }
+
+    (*config).is_require_allowed = is_require_allowed;
+    (*config).reset = reset;
+    (*config).jump_to_alias = jump_to_alias;
+    (*config).to_parent = to_parent;
+    (*config).to_child = to_child;
+    (*config).is_module_present = is_module_present;
+    (*config).get_chunkname = get_chunkname;
+    (*config).get_loadname = get_loadname;
+    (*config).get_cache_key = get_cache_key;
+    (*config).is_config_present = is_config_present;
+    (*config).get_alias = None;
+    (*config).get_config = Some(get_config);
+    (*config).load = load;
+}
+
+/// Helper function to write data to a buffer
+#[cfg(feature = "luau")]
+unsafe fn write_to_buffer(
+    buffer: *mut c_char,
+    buffer_size: usize,
+    size_out: *mut usize,
+    data: &[u8],
+) -> WriteResult {
+    // the buffer must be null terminated as it's a c++ `std::string` data() buffer
+    let is_null_terminated = data.last() == Some(&0);
+    *size_out = data.len() + if is_null_terminated { 0 } else { 1 };
+    if *size_out > buffer_size {
+        return WriteResult::BufferTooSmall;
+    }
+    ptr::copy_nonoverlapping(data.as_ptr(), buffer as *mut _, data.len());
+    if !is_null_terminated {
+        *buffer.add(data.len()) = 0;
+    }
+    WriteResult::Success
+}
+
+#[cfg(feature = "luau")]
+pub(super) fn create_require_function<R: Require + MaybeSend + 'static>(
+    lua: &Lua,
+    require: R,
+) -> Result<Function> {
+    unsafe extern "C-unwind" fn find_current_file(state: *mut ffi::lua_State) -> c_int {
+        let mut ar: ffi::lua_Debug = mem::zeroed();
+        for level in 2.. {
+            if ffi::lua_getinfo(state, level, cstr!("s"), &mut ar) == 0 {
+                ffi::luaL_error(state, cstr!("require is not supported in this context"));
+            }
+            if CStr::from_ptr(ar.what) != c"C" {
+                break;
+            }
+        }
+        ffi::lua_pushstring(state, ar.source);
+        1
+    }
+
+    unsafe extern "C-unwind" fn get_cache_key(state: *mut ffi::lua_State) -> c_int {
+        let ctx = ffi::lua_touserdata(state, ffi::lua_upvalueindex(1));
+        let ctx = try_borrow!(state, ctx);
+        let cache_key = ctx.cache_key();
+        ffi::lua_pushlstring(state, cache_key.as_ptr() as *const _, cache_key.len());
+        1
+    }
+
+    let (get_cache_key, find_current_file, proxyrequire, registered_modules, loader_cache) = unsafe {
+        lua.exec_raw::<(Function, Function, Function, Table, Table)>((), move |state| {
+            let context = Context(Box::new(require));
+            let context_ptr = ffi::lua_newuserdata_t(state, RefCell::new(context));
+            ffi::lua_pushcclosured(state, get_cache_key, cstr!("get_cache_key"), 1);
+            ffi::lua_pushcfunctiond(state, find_current_file, cstr!("find_current_file"));
+            ffi::luarequire_pushproxyrequire(state, init_config, context_ptr as *mut _);
+            ffi::luaL_getsubtable(state, ffi::LUA_REGISTRYINDEX, ffi::LUA_REGISTERED_MODULES_TABLE);
+            ffi::luaL_getsubtable(state, ffi::LUA_REGISTRYINDEX, cstr!("__MLUA_LOADER_CACHE"));
+        })
+    }?;
+
+    unsafe extern "C-unwind" fn error(state: *mut ffi::lua_State) -> c_int {
+        ffi::luaL_where(state, 1);
+        ffi::lua_pushvalue(state, 1);
+        ffi::lua_concat(state, 2);
+        ffi::lua_error(state);
+    }
+
+    unsafe extern "C-unwind" fn r#type(state: *mut ffi::lua_State) -> c_int {
+        ffi::lua_pushstring(state, ffi::lua_typename(state, ffi::lua_type(state, 1)));
+        1
+    }
+
+    let (error, r#type) = unsafe {
+        lua.exec_raw::<(Function, Function)>((), move |state| {
+            ffi::lua_pushcfunctiond(state, error, cstr!("error"));
+            ffi::lua_pushcfunctiond(state, r#type, cstr!("type"));
+        })
+    }?;
+
+    // Prepare environment for the "require" function
+    let env = lua.create_table_with_capacity(0, 7)?;
+    env.raw_set("get_cache_key", get_cache_key)?;
+    env.raw_set("find_current_file", find_current_file)?;
+    env.raw_set("proxyrequire", proxyrequire)?;
+    env.raw_set("REGISTERED_MODULES", registered_modules)?;
+    env.raw_set("LOADER_CACHE", loader_cache)?;
+    env.raw_set("error", error)?;
+    env.raw_set("type", r#type)?;
+
+    lua.load(
+        r#"
+        local path = ...
+        if type(path) ~= "string" then
+            error("bad argument #1 to 'require' (string expected, got " .. type(path) .. ")")
+        end
+
+        -- Check if the module (path) is explicitly registered
+        local maybe_result = REGISTERED_MODULES[path]
+        if maybe_result ~= nil then
+            return maybe_result
+        end
+
+        local loader = proxyrequire(path, find_current_file())
+        local cache_key = get_cache_key()
+        -- Check if the loader result is already cached
+        local result = LOADER_CACHE[cache_key]
+        if result ~= nil then
+            return result
+        end
+
+        -- Call the loader function and cache the result
+        result = loader()
+        if result == nil then
+            result = true
+        end
+        LOADER_CACHE[cache_key] = result
+        return result
+        "#,
+    )
+    .try_cache()
+    .set_name("=__mlua_require")
+    .set_environment(env)
+    .into_function()
+}
+
+#[cfg(test)]
+mod tests {
+    use std::path::Path;
+
+    use super::TextRequirer;
+
+    #[test]
+    fn test_path_normalize() {
+        for (input, expected) in [
+            // Basic formatting checks
+            ("", "./"),
+            (".", "./"),
+            ("a/relative/path", "./a/relative/path"),
+            // Paths containing extraneous '.' and '/' symbols
+            ("./remove/extraneous/symbols/", "./remove/extraneous/symbols"),
+            ("./remove/extraneous//symbols", "./remove/extraneous/symbols"),
+            ("./remove/extraneous/symbols/.", "./remove/extraneous/symbols"),
+            ("./remove/extraneous/./symbols", "./remove/extraneous/symbols"),
+            ("../remove/extraneous/symbols/", "../remove/extraneous/symbols"),
+            ("../remove/extraneous//symbols", "../remove/extraneous/symbols"),
+            ("../remove/extraneous/symbols/.", "../remove/extraneous/symbols"),
+            ("../remove/extraneous/./symbols", "../remove/extraneous/symbols"),
+            ("/remove/extraneous/symbols/", "/remove/extraneous/symbols"),
+            ("/remove/extraneous//symbols", "/remove/extraneous/symbols"),
+            ("/remove/extraneous/symbols/.", "/remove/extraneous/symbols"),
+            ("/remove/extraneous/./symbols", "/remove/extraneous/symbols"),
+            // Paths containing '..'
+            ("./remove/me/..", "./remove"),
+            ("./remove/me/../", "./remove"),
+            ("../remove/me/..", "../remove"),
+            ("../remove/me/../", "../remove"),
+            ("/remove/me/..", "/remove"),
+            ("/remove/me/../", "/remove"),
+            ("./..", "../"),
+            ("./../", "../"),
+            ("../..", "../../"),
+            ("../../", "../../"),
+            // '..' disappears if path is absolute and component is non-erasable
+            ("/../", "/"),
+        ] {
+            let path = TextRequirer::normalize_path(input.as_ref());
+            assert_eq!(
+                &path,
+                expected.as_ref() as &Path,
+                "wrong normalization for {input}"
+            );
+        }
+    }
+}

src/memory.rs

@@ -18,15 +18,32 @@ pub(crate) struct MemoryState {
 }
 
 impl MemoryState {
+    #[cfg(feature = "luau")]
     #[inline]
     pub(crate) unsafe fn get(state: *mut ffi::lua_State) -> *mut Self {
         let mut mem_state = ptr::null_mut();
-        #[cfg(feature = "luau")]
-        {
-            ffi::lua_getallocf(state, &mut mem_state);
-            mlua_assert!(!mem_state.is_null(), "Luau state has no allocator userdata");
+        ffi::lua_getallocf(state, &mut mem_state);
+        mlua_assert!(!mem_state.is_null(), "Luau state has no allocator userdata");
+        mem_state as *mut MemoryState
+    }
+
+    #[cfg(not(feature = "luau"))]
+    #[rustversion::since(1.85)]
+    #[inline]
+    #[allow(clippy::incompatible_msrv)]
+    pub(crate) unsafe fn get(state: *mut ffi::lua_State) -> *mut Self {
+        let mut mem_state = ptr::null_mut();
+        if !ptr::fn_addr_eq(ffi::lua_getallocf(state, &mut mem_state), ALLOCATOR) {
+            mem_state = ptr::null_mut();
         }
-        #[cfg(not(feature = "luau"))]
+        mem_state as *mut MemoryState
+    }
+
+    #[cfg(not(feature = "luau"))]
+    #[rustversion::before(1.85)]
+    #[inline]
+    pub(crate) unsafe fn get(state: *mut ffi::lua_State) -> *mut Self {
+        let mut mem_state = ptr::null_mut();
         if ffi::lua_getallocf(state, &mut mem_state) != ALLOCATOR {
             mem_state = ptr::null_mut();
         }
@@ -80,7 +97,7 @@ impl MemoryState {
     }
 }
 
-unsafe extern "C-unwind" fn allocator(
+unsafe extern "C" fn allocator(
     extra: *mut c_void,
     ptr: *mut c_void,
     osize: usize,

src/multi.rs

@@ -1,14 +1,17 @@
+use std::collections::{vec_deque, VecDeque};
 use std::iter::FromIterator;
+use std::mem;
 use std::ops::{Deref, DerefMut};
 use std::os::raw::c_int;
 use std::result::Result as StdResult;
 
 use crate::error::Result;
 use crate::state::{Lua, RawLua};
+use crate::traits::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti};
 use crate::util::check_stack;
-use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, MultiValue, Nil};
+use crate::value::{Nil, Value};
 
-/// Result is convertible to `MultiValue` following the common Lua idiom of returning the result
+/// Result is convertible to [`MultiValue`] following the common Lua idiom of returning the result
 /// on success, or in the case of an error, returning `nil` and an error message.
 impl<T: IntoLua, E: IntoLua> IntoLuaMulti for StdResult<T, E> {
     #[inline]
@@ -89,6 +92,111 @@ impl<T: FromLua> FromLuaMulti for T {
     }
 }
 
+/// Multiple Lua values used for both argument passing and also for multiple return values.
+#[derive(Default, Debug, Clone)]
+pub struct MultiValue(VecDeque<Value>);
+
+impl Deref for MultiValue {
+    type Target = VecDeque<Value>;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl DerefMut for MultiValue {
+    #[inline]
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
+impl MultiValue {
+    /// Creates an empty `MultiValue` containing no values.
+    #[inline]
+    pub const fn new() -> MultiValue {
+        MultiValue(VecDeque::new())
+    }
+
+    /// Creates an empty `MultiValue` container with space for at least `capacity` elements.
+    pub fn with_capacity(capacity: usize) -> MultiValue {
+        MultiValue(VecDeque::with_capacity(capacity))
+    }
+
+    /// Creates a `MultiValue` container from vector of values.
+    ///
+    /// This method works in *O*(1) time and does not allocate any additional memory.
+    #[inline]
+    pub fn from_vec(vec: Vec<Value>) -> MultiValue {
+        vec.into()
+    }
+
+    /// Consumes the `MultiValue` and returns a vector of values.
+    ///
+    /// This method needs *O*(*n*) data movement if the circular buffer doesn't happen to be at the
+    /// beginning of the allocation.
+    #[inline]
+    pub fn into_vec(self) -> Vec<Value> {
+        self.into()
+    }
+
+    #[inline]
+    pub(crate) fn from_lua_iter<T: IntoLua>(lua: &Lua, iter: impl IntoIterator<Item = T>) -> Result<Self> {
+        let iter = iter.into_iter();
+        let mut multi_value = MultiValue::with_capacity(iter.size_hint().0);
+        for value in iter {
+            multi_value.push_back(value.into_lua(lua)?);
+        }
+        Ok(multi_value)
+    }
+}
+
+impl From<Vec<Value>> for MultiValue {
+    #[inline]
+    fn from(value: Vec<Value>) -> Self {
+        MultiValue(value.into())
+    }
+}
+
+impl From<MultiValue> for Vec<Value> {
+    #[inline]
+    fn from(value: MultiValue) -> Self {
+        value.0.into()
+    }
+}
+
+impl FromIterator<Value> for MultiValue {
+    #[inline]
+    fn from_iter<I: IntoIterator<Item = Value>>(iter: I) -> Self {
+        let mut multi_value = MultiValue::new();
+        multi_value.extend(iter);
+        multi_value
+    }
+}
+
+impl IntoIterator for MultiValue {
+    type Item = Value;
+    type IntoIter = vec_deque::IntoIter<Value>;
+
+    #[inline]
+    fn into_iter(mut self) -> Self::IntoIter {
+        let deque = mem::take(&mut self.0);
+        mem::forget(self);
+        deque.into_iter()
+    }
+}
+
+impl<'a> IntoIterator for &'a MultiValue {
+    type Item = &'a Value;
+    type IntoIter = vec_deque::Iter<'a, Value>;
+
+    #[inline]
+    fn into_iter(self) -> Self::IntoIter {
+        self.0.iter()
+    }
+}
+
 impl IntoLuaMulti for MultiValue {
     #[inline]
     fn into_lua_multi(self, _: &Lua) -> Result<MultiValue> {
@@ -126,10 +234,7 @@ impl FromLuaMulti for MultiValue {
 /// # Ok(())
 /// # }
 /// ```
-///
-/// [`FromLua`]: crate::FromLua
-/// [`MultiValue`]: crate::MultiValue
-#[derive(Debug, Clone)]
+#[derive(Default, Debug, Clone)]
 pub struct Variadic<T>(Vec<T>);
 
 impl<T> Variadic<T> {
@@ -137,11 +242,38 @@ impl<T> Variadic<T> {
     pub const fn new() -> Variadic<T> {
         Variadic(Vec::new())
     }
+
+    /// Creates an empty `Variadic` container with space for at least `capacity` elements.
+    pub fn with_capacity(capacity: usize) -> Variadic<T> {
+        Variadic(Vec::with_capacity(capacity))
+    }
 }
 
-impl<T> Default for Variadic<T> {
-    fn default() -> Variadic<T> {
-        const { Variadic::new() }
+impl<T> Deref for Variadic<T> {
+    type Target = Vec<T>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl<T> DerefMut for Variadic<T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
+impl<T> From<Vec<T>> for Variadic<T> {
+    #[inline]
+    fn from(vec: Vec<T>) -> Self {
+        Variadic(vec)
+    }
+}
+
+impl<T> From<Variadic<T>> for Vec<T> {
+    #[inline]
+    fn from(value: Variadic<T>) -> Self {
+        value.0
     }
 }
 
@@ -160,20 +292,6 @@ impl<T> IntoIterator for Variadic<T> {
     }
 }
 
-impl<T> Deref for Variadic<T> {
-    type Target = Vec<T>;
-
-    fn deref(&self) -> &Self::Target {
-        &self.0
-    }
-}
-
-impl<T> DerefMut for Variadic<T> {
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        &mut self.0
-    }
-}
-
 impl<T: IntoLua> IntoLuaMulti for Variadic<T> {
     #[inline]
     fn into_lua_multi(self, lua: &Lua) -> Result<MultiValue> {
@@ -213,10 +331,7 @@ macro_rules! impl_tuple {
             }
 
             #[inline]
-            unsafe fn from_stack_multi(nvals: c_int, lua: &RawLua) -> Result<Self> {
-                if nvals > 0 {
-                    ffi::lua_pop(lua.state(), nvals);
-                }
+            unsafe fn from_stack_multi(_nvals: c_int, _lua: &RawLua) -> Result<Self> {
                 Ok(())
             }
         }
@@ -342,3 +457,13 @@ impl_tuple!(A B C D E F G H I J K L M);
 impl_tuple!(A B C D E F G H I J K L M N);
 impl_tuple!(A B C D E F G H I J K L M N O);
 impl_tuple!(A B C D E F G H I J K L M N O P);
+
+#[cfg(test)]
+mod assertions {
+    use super::*;
+
+    #[cfg(not(feature = "send"))]
+    static_assertions::assert_not_impl_any!(MultiValue: Send);
+    #[cfg(feature = "send")]
+    static_assertions::assert_impl_all!(MultiValue: Send, Sync);
+}

src/prelude.rs

@@ -2,17 +2,19 @@
 
 #[doc(no_inline)]
 pub use crate::{
-    AnyUserData as LuaAnyUserData, Chunk as LuaChunk, Error as LuaError, ErrorContext as LuaErrorContext,
+    AnyUserData as LuaAnyUserData, BorrowedBytes as LuaBorrowedBytes, BorrowedStr as LuaBorrowedStr,
+    Chunk as LuaChunk, Either as LuaEither, Error as LuaError, ErrorContext as LuaErrorContext,
     ExternalError as LuaExternalError, ExternalResult as LuaExternalResult, FromLua, FromLuaMulti,
     Function as LuaFunction, FunctionInfo as LuaFunctionInfo, GCMode as LuaGCMode, Integer as LuaInteger,
-    IntoLua, IntoLuaMulti, LightUserData as LuaLightUserData, Lua, LuaOptions, MetaMethod as LuaMetaMethod,
-    MultiValue as LuaMultiValue, Nil as LuaNil, Number as LuaNumber, ObjectLike as LuaObjectLike,
-    RegistryKey as LuaRegistryKey, Result as LuaResult, StdLib as LuaStdLib, String as LuaString,
-    Table as LuaTable, TablePairs as LuaTablePairs, TableSequence as LuaTableSequence, Thread as LuaThread,
-    ThreadStatus as LuaThreadStatus, UserData as LuaUserData, UserDataFields as LuaUserDataFields,
-    UserDataMetatable as LuaUserDataMetatable, UserDataMethods as LuaUserDataMethods,
-    UserDataRef as LuaUserDataRef, UserDataRefMut as LuaUserDataRefMut,
-    UserDataRegistry as LuaUserDataRegistry, Value as LuaValue,
+    IntoLua, IntoLuaMulti, LightUserData as LuaLightUserData, Lua, LuaNativeFn, LuaNativeFnMut, LuaOptions,
+    MetaMethod as LuaMetaMethod, MultiValue as LuaMultiValue, Nil as LuaNil, Number as LuaNumber,
+    ObjectLike as LuaObjectLike, RegistryKey as LuaRegistryKey, Result as LuaResult, StdLib as LuaStdLib,
+    String as LuaString, Table as LuaTable, TablePairs as LuaTablePairs, TableSequence as LuaTableSequence,
+    Thread as LuaThread, ThreadStatus as LuaThreadStatus, UserData as LuaUserData,
+    UserDataFields as LuaUserDataFields, UserDataMetatable as LuaUserDataMetatable,
+    UserDataMethods as LuaUserDataMethods, UserDataRef as LuaUserDataRef,
+    UserDataRefMut as LuaUserDataRefMut, UserDataRegistry as LuaUserDataRegistry, Value as LuaValue,
+    Variadic as LuaVariadic, VmState as LuaVmState, WeakLua,
 };
 
 #[cfg(not(feature = "luau"))]
@@ -21,13 +23,17 @@ pub use crate::HookTriggers as LuaHookTriggers;
 
 #[cfg(feature = "luau")]
 #[doc(no_inline)]
-pub use crate::{CoverageInfo as LuaCoverageInfo, Vector as LuaVector, VmState as LuaVmState};
+pub use crate::{
+    CompileConstant as LuaCompileConstant, CoverageInfo as LuaCoverageInfo,
+    NavigateError as LuaNavigateError, Require as LuaRequire, TextRequirer as LuaTextRequirer,
+    Vector as LuaVector,
+};
 
 #[cfg(feature = "async")]
 #[doc(no_inline)]
-pub use crate::AsyncThread as LuaAsyncThread;
+pub use crate::{AsyncThread as LuaAsyncThread, LuaNativeAsyncFn};
 
-#[cfg(feature = "serialize")]
+#[cfg(feature = "serde")]
 #[doc(no_inline)]
 pub use crate::{
     DeserializeOptions as LuaDeserializeOptions, LuaSerdeExt, SerializeOptions as LuaSerializeOptions,

src/serde/de.rs

@@ -1,3 +1,5 @@
+//! Deserialize Lua values to a Rust data structure.
+
 use std::cell::RefCell;
 use std::os::raw::c_void;
 use std::rc::Rc;
@@ -47,6 +49,11 @@ pub struct Options {
     ///
     /// Default: **false**
     pub sort_keys: bool,
+
+    /// If true, empty Lua tables will be encoded as array, instead of map.
+    ///
+    /// Default: **false**
+    pub encode_empty_tables_as_array: bool,
 }
 
 impl Default for Options {
@@ -62,6 +69,7 @@ impl Options {
             deny_unsupported_types: true,
             deny_recursive_tables: true,
             sort_keys: false,
+            encode_empty_tables_as_array: false,
         }
     }
 
@@ -91,15 +99,24 @@ impl Options {
         self.sort_keys = enabled;
         self
     }
+
+    /// Sets [`encode_empty_tables_as_array`] option.
+    ///
+    /// [`encode_empty_tables_as_array`]: #structfield.encode_empty_tables_as_array
+    #[must_use]
+    pub const fn encode_empty_tables_as_array(mut self, enabled: bool) -> Self {
+        self.encode_empty_tables_as_array = enabled;
+        self
+    }
 }
 
 impl Deserializer {
-    /// Creates a new Lua Deserializer for the `Value`.
+    /// Creates a new Lua Deserializer for the [`Value`].
     pub fn new(value: Value) -> Self {
         Self::new_with_options(value, Options::default())
     }
 
-    /// Creates a new Lua Deserializer for the `Value` with custom options.
+    /// Creates a new Lua Deserializer for the [`Value`] with custom options.
     pub fn new_with_options(value: Value, options: Options) -> Self {
         Deserializer {
             value,
@@ -139,25 +156,25 @@ impl<'de> serde::Deserializer<'de> for Deserializer {
                 Err(_) => visitor.visit_bytes(&s.as_bytes()),
             },
             Value::Table(ref t) if t.raw_len() > 0 || t.is_array() => self.deserialize_seq(visitor),
+            Value::Table(ref t) if self.options.encode_empty_tables_as_array && t.is_empty() => {
+                self.deserialize_seq(visitor)
+            }
             Value::Table(_) => self.deserialize_map(visitor),
             Value::LightUserData(ud) if ud.0.is_null() => visitor.visit_none(),
             Value::UserData(ud) if ud.is_serializable() => {
                 serde_userdata(ud, |value| value.deserialize_any(visitor))
             }
             #[cfg(feature = "luau")]
-            Value::UserData(ud) if ud.1 == crate::types::SubtypeId::Buffer => unsafe {
-                let lua = ud.0.lua.lock();
-                let mut size = 0usize;
-                let buf = ffi::lua_tobuffer(lua.ref_thread(), ud.0.index, &mut size);
-                mlua_assert!(!buf.is_null(), "invalid Luau buffer");
-                let buf = std::slice::from_raw_parts(buf as *const u8, size);
-                visitor.visit_bytes(buf)
-            },
+            Value::Buffer(buf) => {
+                let lua = buf.0.lua.lock();
+                visitor.visit_bytes(buf.as_slice(&lua))
+            }
             Value::Function(_)
             | Value::Thread(_)
             | Value::UserData(_)
             | Value::LightUserData(_)
-            | Value::Error(_) => {
+            | Value::Error(_)
+            | Value::Other(_) => {
                 if self.options.deny_unsupported_types {
                     let msg = format!("unsupported value type `{}`", self.value.type_name());
                     Err(de::Error::custom(msg))
@@ -424,7 +441,7 @@ impl<'de> de::SeqAccess<'de> for SeqDeserializer<'_> {
 
 #[cfg(feature = "luau")]
 struct VecDeserializer {
-    vec: crate::types::Vector,
+    vec: crate::Vector,
     next: usize,
     options: Options,
     visited: Rc<RefCell<FxHashSet<*const c_void>>>,
@@ -450,7 +467,7 @@ impl<'de> de::SeqAccess<'de> for VecDeserializer {
     }
 
     fn size_hint(&self) -> Option<usize> {
-        Some(crate::types::Vector::SIZE)
+        Some(crate::Vector::SIZE)
     }
 }
 
@@ -463,7 +480,7 @@ impl<'a> MapPairs<'a> {
     pub(crate) fn new(t: &'a Table, sort_keys: bool) -> Result<Self> {
         if sort_keys {
             let mut pairs = t.pairs::<Value, Value>().collect::<Result<Vec<_>>>()?;
-            pairs.sort_by(|(a, _), (b, _)| b.cmp(a)); // reverse order as we pop values from the end
+            pairs.sort_by(|(a, _), (b, _)| b.sort_cmp(a)); // reverse order as we pop values from the end
             Ok(MapPairs::Vec(pairs))
         } else {
             Ok(MapPairs::Iter(t.pairs::<Value, Value>()))
@@ -504,7 +521,7 @@ struct MapDeserializer<'a> {
     processed: usize,
 }
 
-impl<'a> MapDeserializer<'a> {
+impl MapDeserializer<'_> {
     fn next_key_deserializer(&mut self) -> Result<Option<Deserializer>> {
         loop {
             match self.pairs.next() {

src/serde/mod.rs

@@ -13,12 +13,10 @@ use crate::util::check_stack;
 use crate::value::Value;
 
 /// Trait for serializing/deserializing Lua values using Serde.
-#[cfg_attr(docsrs, doc(cfg(feature = "serialize")))]
+#[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
 pub trait LuaSerdeExt: Sealed {
     /// A special value (lightuserdata) to encode/decode optional (none) values.
     ///
-    /// Requires `feature = "serialize"`
-    ///
     /// # Example
     ///
     /// ```
@@ -42,8 +40,6 @@ pub trait LuaSerdeExt: Sealed {
     /// As result, encoded Array will contain only sequence part of the table, with the same length
     /// as the `#` operator on that table.
     ///
-    /// Requires `feature = "serialize"`
-    ///
     /// # Example
     ///
     /// ```
@@ -71,8 +67,6 @@ pub trait LuaSerdeExt: Sealed {
 
     /// Converts `T` into a [`Value`] instance.
     ///
-    /// Requires `feature = "serialize"`
-    ///
     /// [`Value`]: crate::Value
     ///
     /// # Example
@@ -104,10 +98,6 @@ pub trait LuaSerdeExt: Sealed {
 
     /// Converts `T` into a [`Value`] instance with options.
     ///
-    /// Requires `feature = "serialize"`
-    ///
-    /// [`Value`]: crate::Value
-    ///
     /// # Example
     ///
     /// ```
@@ -131,10 +121,6 @@ pub trait LuaSerdeExt: Sealed {
 
     /// Deserializes a [`Value`] into any serde deserializable object.
     ///
-    /// Requires `feature = "serialize"`
-    ///
-    /// [`Value`]: crate::Value
-    ///
     /// # Example
     ///
     /// ```
@@ -162,10 +148,6 @@ pub trait LuaSerdeExt: Sealed {
 
     /// Deserializes a [`Value`] into any serde deserializable object with options.
     ///
-    /// Requires `feature = "serialize"`
-    ///
-    /// [`Value`]: crate::Value
-    ///
     /// # Example
     ///
     /// ```

src/serde/ser.rs

@@ -1,10 +1,13 @@
+//! Serialize a Rust data structure into Lua value.
+
 use serde::{ser, Serialize};
 
 use super::LuaSerdeExt;
 use crate::error::{Error, Result};
 use crate::state::Lua;
 use crate::table::Table;
-use crate::value::{IntoLua, Value};
+use crate::traits::IntoLua;
+use crate::value::Value;
 
 /// A struct for serializing Rust values into Lua values.
 #[derive(Debug)]
@@ -253,7 +256,7 @@ impl<'a> ser::Serializer for Serializer<'a> {
     fn serialize_seq(self, len: Option<usize>) -> Result<Self::SerializeSeq> {
         let table = self.lua.create_table_with_capacity(len.unwrap_or(0), 0)?;
         if self.options.set_array_metatable {
-            table.set_metatable(Some(self.lua.array_metatable()));
+            table.set_metatable(Some(self.lua.array_metatable()))?;
         }
         Ok(SerializeSeq::new(self.lua, table, self.options))
     }
@@ -266,7 +269,7 @@ impl<'a> ser::Serializer for Serializer<'a> {
     #[inline]
     fn serialize_tuple_struct(self, name: &'static str, len: usize) -> Result<Self::SerializeTupleStruct> {
         #[cfg(feature = "luau")]
-        if name == "Vector" && len == crate::types::Vector::SIZE {
+        if name == "Vector" && len == crate::Vector::SIZE {
             return Ok(SerializeSeq::new_vector(self.lua, self.options));
         }
         _ = name;
@@ -340,7 +343,7 @@ impl<'a> ser::Serializer for Serializer<'a> {
 pub struct SerializeSeq<'a> {
     lua: &'a Lua,
     #[cfg(feature = "luau")]
-    vector: Option<crate::types::Vector>,
+    vector: Option<crate::Vector>,
     table: Option<Table>,
     next: usize,
     options: Options,
@@ -362,7 +365,7 @@ impl<'a> SerializeSeq<'a> {
     const fn new_vector(lua: &'a Lua, options: Options) -> Self {
         Self {
             lua,
-            vector: Some(crate::types::Vector::zero()),
+            vector: Some(crate::Vector::zero()),
             table: None,
             next: 0,
             options,
@@ -526,8 +529,8 @@ impl ser::SerializeStruct for SerializeStruct<'_> {
     fn end(self) -> Result<Value> {
         match self.inner {
             Some(table @ Value::Table(_)) => Ok(table),
-            Some(value) if self.options.detect_serde_json_arbitrary_precision => {
-                let number_s = value.as_str().expect("not an arbitrary precision number");
+            Some(value @ Value::String(_)) if self.options.detect_serde_json_arbitrary_precision => {
+                let number_s = value.to_string()?;
                 if number_s.contains(['.', 'e', 'E']) {
                     if let Ok(number) = number_s.parse().map(Value::Number) {
                         return Ok(number);

src/state/extra.rs

@@ -13,6 +13,7 @@ use crate::error::Result;
 use crate::state::RawLua;
 use crate::stdlib::StdLib;
 use crate::types::{AppData, ReentrantMutex, XRc};
+use crate::userdata::RawUserDataRegistry;
 use crate::util::{get_internal_metatable, push_internal_userdata, TypeKey, WrappedFailure};
 
 #[cfg(any(feature = "luau", doc))]
@@ -26,8 +27,8 @@ use super::{Lua, WeakLua};
 // Unique key to store `ExtraData` in the registry
 static EXTRA_REGISTRY_KEY: u8 = 0;
 
-const WRAPPED_FAILURE_POOL_SIZE: usize = 64;
-const REF_STACK_RESERVE: c_int = 1;
+const WRAPPED_FAILURE_POOL_DEFAULT_CAPACITY: usize = 64;
+const REF_STACK_RESERVE: c_int = 3;
 
 /// Data associated with the Lua state.
 pub(crate) struct ExtraData {
@@ -35,15 +36,17 @@ pub(crate) struct ExtraData {
     pub(super) weak: MaybeUninit<WeakLua>,
     pub(super) owned: bool,
 
-    pub(super) registered_userdata: FxHashMap<TypeId, c_int>,
+    pub(super) pending_userdata_reg: FxHashMap<TypeId, RawUserDataRegistry>,
+    pub(super) registered_userdata_t: FxHashMap<TypeId, c_int>,
     pub(super) registered_userdata_mt: FxHashMap<*const c_void, Option<TypeId>>,
     pub(super) last_checked_userdata_mt: (*const c_void, Option<TypeId>),
 
     // When Lua instance dropped, setting `None` would prevent collecting `RegistryKey`s
     pub(super) registry_unref_list: Arc<Mutex<Option<Vec<c_int>>>>,
 
-    // Container to store arbitrary data (extensions)
+    // Containers to store arbitrary data (extensions)
     pub(super) app_data: AppData,
+    pub(super) app_data_priv: AppData,
 
     pub(super) safe: bool,
     pub(super) libs: StdLib,
@@ -58,6 +61,7 @@ pub(crate) struct ExtraData {
 
     // Pool of `WrappedFailure` enums in the ref thread (as userdata)
     pub(super) wrapped_failure_pool: Vec<c_int>,
+    pub(super) wrapped_failure_top: usize,
     // Pool of `Thread`s (coroutines) for async execution
     #[cfg(feature = "async")]
     pub(super) thread_pool: Vec<c_int>,
@@ -72,14 +76,20 @@ pub(crate) struct ExtraData {
     #[cfg(not(feature = "luau"))]
     pub(super) hook_callback: Option<crate::types::HookCallback>,
     #[cfg(not(feature = "luau"))]
-    pub(super) hook_thread: *mut ffi::lua_State,
+    pub(super) hook_triggers: crate::debug::HookTriggers,
     #[cfg(feature = "lua54")]
     pub(super) warn_callback: Option<crate::types::WarnCallback>,
     #[cfg(feature = "luau")]
     pub(super) interrupt_callback: Option<crate::types::InterruptCallback>,
+    #[cfg(feature = "luau")]
+    pub(super) thread_creation_callback: Option<crate::types::ThreadCreationCallback>,
+    #[cfg(feature = "luau")]
+    pub(super) thread_collection_callback: Option<crate::types::ThreadCollectionCallback>,
 
     #[cfg(feature = "luau")]
-    pub(super) sandboxed: bool,
+    pub(crate) running_gc: bool,
+    #[cfg(feature = "luau")]
+    pub(crate) sandboxed: bool,
     #[cfg(feature = "luau")]
     pub(super) compiler: Option<Compiler>,
     #[cfg(feature = "luau-jit")]
@@ -144,11 +154,13 @@ impl ExtraData {
             lua: MaybeUninit::uninit(),
             weak: MaybeUninit::uninit(),
             owned,
-            registered_userdata: FxHashMap::default(),
+            pending_userdata_reg: FxHashMap::default(),
+            registered_userdata_t: FxHashMap::default(),
             registered_userdata_mt: FxHashMap::default(),
             last_checked_userdata_mt: (ptr::null(), None),
             registry_unref_list: Arc::new(Mutex::new(Some(Vec::new()))),
             app_data: AppData::default(),
+            app_data_priv: AppData::default(),
             safe: false,
             libs: StdLib::NONE,
             skip_memory_check: false,
@@ -157,7 +169,8 @@ impl ExtraData {
             ref_stack_size: ffi::LUA_MINSTACK - REF_STACK_RESERVE,
             ref_stack_top: ffi::lua_gettop(ref_thread),
             ref_free: Vec::new(),
-            wrapped_failure_pool: Vec::with_capacity(WRAPPED_FAILURE_POOL_SIZE),
+            wrapped_failure_pool: Vec::with_capacity(WRAPPED_FAILURE_POOL_DEFAULT_CAPACITY),
+            wrapped_failure_top: 0,
             #[cfg(feature = "async")]
             thread_pool: Vec::new(),
             wrapped_failure_mt_ptr,
@@ -166,17 +179,23 @@ impl ExtraData {
             #[cfg(not(feature = "luau"))]
             hook_callback: None,
             #[cfg(not(feature = "luau"))]
-            hook_thread: ptr::null_mut(),
+            hook_triggers: Default::default(),
             #[cfg(feature = "lua54")]
             warn_callback: None,
             #[cfg(feature = "luau")]
             interrupt_callback: None,
             #[cfg(feature = "luau")]
+            thread_creation_callback: None,
+            #[cfg(feature = "luau")]
+            thread_collection_callback: None,
+            #[cfg(feature = "luau")]
             sandboxed: false,
             #[cfg(feature = "luau")]
             compiler: None,
             #[cfg(feature = "luau-jit")]
             enable_jit: true,
+            #[cfg(feature = "luau")]
+            running_gc: false,
         }));
 
         // Store it in the registry
@@ -190,13 +209,10 @@ impl ExtraData {
             raw: XRc::clone(raw),
             collect_garbage: false,
         });
-        if self.owned {
-            XRc::decrement_strong_count(XRc::as_ptr(raw));
-        }
         self.weak.write(WeakLua(XRc::downgrade(raw)));
     }
 
-    pub(super) unsafe fn get(state: *mut ffi::lua_State) -> *mut Self {
+    pub(crate) unsafe fn get(state: *mut ffi::lua_State) -> *mut Self {
         #[cfg(feature = "luau")]
         if cfg!(not(feature = "module")) {
             // In the main app we can use `lua_callbacks` to access ExtraData
@@ -235,7 +251,7 @@ impl ExtraData {
     }
 
     #[inline(always)]
-    pub(super) unsafe fn raw_lua(&self) -> &RawLua {
+    pub(crate) unsafe fn raw_lua(&self) -> &RawLua {
         &*self.lua.assume_init_ref().raw.data_ptr()
     }
 
@@ -243,4 +259,32 @@ impl ExtraData {
     pub(super) unsafe fn weak(&self) -> &WeakLua {
         self.weak.assume_init_ref()
     }
+
+    /// Pops a reference from top of the auxiliary stack and move it to a first free slot.
+    pub(super) unsafe fn ref_stack_pop(&mut self) -> c_int {
+        if let Some(free) = self.ref_free.pop() {
+            ffi::lua_replace(self.ref_thread, free);
+            return free;
+        }
+
+        // Try to grow max stack size
+        if self.ref_stack_top >= self.ref_stack_size {
+            let mut inc = self.ref_stack_size; // Try to double stack size
+            while inc > 0 && ffi::lua_checkstack(self.ref_thread, inc) == 0 {
+                inc /= 2;
+            }
+            if inc == 0 {
+                // Pop item on top of the stack to avoid stack leaking and successfully run destructors
+                // during unwinding.
+                ffi::lua_pop(self.ref_thread, 1);
+                let top = self.ref_stack_top;
+                // It is a user error to create too many references to exhaust the Lua max stack size
+                // for the ref thread.
+                panic!("cannot create a Lua reference, out of auxiliary stack space (used {top} slots)");
+            }
+            self.ref_stack_size += inc;
+        }
+        self.ref_stack_top += 1;
+        self.ref_stack_top
+    }
 }

src/state/util.rs

@@ -7,28 +7,27 @@ use crate::error::{Error, Result};
 use crate::state::{ExtraData, RawLua};
 use crate::util::{self, get_internal_metatable, WrappedFailure};
 
-const WRAPPED_FAILURE_POOL_SIZE: usize = 64;
-
-pub(super) struct StateGuard<'a>(&'a RawLua, *mut ffi::lua_State);
+struct StateGuard<'a>(&'a RawLua, *mut ffi::lua_State);
 
 impl<'a> StateGuard<'a> {
-    pub(super) fn new(inner: &'a RawLua, mut state: *mut ffi::lua_State) -> Self {
+    fn new(inner: &'a RawLua, mut state: *mut ffi::lua_State) -> Self {
         state = inner.state.replace(state);
         Self(inner, state)
     }
 }
 
-impl<'a> Drop for StateGuard<'a> {
+impl Drop for StateGuard<'_> {
     fn drop(&mut self) {
         self.0.state.set(self.1);
     }
 }
 
 // An optimized version of `callback_error` that does not allocate `WrappedFailure` userdata
-// and instead reuses unsed values from previous calls (or allocates new).
-pub(super) unsafe fn callback_error_ext<F, R>(
+// and instead reuses unused values from previous calls (or allocates new).
+pub(crate) unsafe fn callback_error_ext<F, R>(
     state: *mut ffi::lua_State,
     mut extra: *mut ExtraData,
+    wrap_error: bool,
     f: F,
 ) -> R
 where
@@ -42,26 +41,27 @@ where
 
     enum PreallocatedFailure {
         New(*mut WrappedFailure),
-        Existing(i32),
+        Reserved,
     }
 
     impl PreallocatedFailure {
         unsafe fn reserve(state: *mut ffi::lua_State, extra: *mut ExtraData) -> Self {
-            match (*extra).wrapped_failure_pool.pop() {
-                Some(index) => PreallocatedFailure::Existing(index),
-                None => {
-                    // We need to check stack for Luau in case when callback is called from interrupt
-                    // See https://github.com/Roblox/luau/issues/446 and mlua #142 and #153
-                    #[cfg(feature = "luau")]
-                    ffi::lua_rawcheckstack(state, 2);
-                    // Place it to the beginning of the stack
-                    let ud = WrappedFailure::new_userdata(state);
-                    ffi::lua_insert(state, 1);
-                    PreallocatedFailure::New(ud)
-                }
+            if (*extra).wrapped_failure_top > 0 {
+                (*extra).wrapped_failure_top -= 1;
+                return PreallocatedFailure::Reserved;
             }
+
+            // We need to check stack for Luau in case when callback is called from interrupt
+            // See https://github.com/luau-lang/luau/issues/446 and mlua #142 and #153
+            #[cfg(feature = "luau")]
+            ffi::lua_rawcheckstack(state, 2);
+            // Place it to the beginning of the stack
+            let ud = WrappedFailure::new_userdata(state);
+            ffi::lua_insert(state, 1);
+            PreallocatedFailure::New(ud)
         }
 
+        #[cold]
         unsafe fn r#use(&self, state: *mut ffi::lua_State, extra: *mut ExtraData) -> *mut WrappedFailure {
             let ref_thread = (*extra).ref_thread;
             match *self {
@@ -69,12 +69,12 @@ where
                     ffi::lua_settop(state, 1);
                     ud
                 }
-                PreallocatedFailure::Existing(index) => {
+                PreallocatedFailure::Reserved => {
+                    let index = (*extra).wrapped_failure_pool.pop().unwrap();
                     ffi::lua_settop(state, 0);
                     #[cfg(feature = "luau")]
                     ffi::lua_rawcheckstack(state, 2);
-                    ffi::lua_pushvalue(ref_thread, index);
-                    ffi::lua_xmove(ref_thread, state, 1);
+                    ffi::lua_xpush(ref_thread, state, index);
                     ffi::lua_pushnil(ref_thread);
                     ffi::lua_replace(ref_thread, index);
                     (*extra).ref_free.push(index);
@@ -87,24 +87,13 @@ where
             let ref_thread = (*extra).ref_thread;
             match self {
                 PreallocatedFailure::New(_) => {
-                    if (*extra).wrapped_failure_pool.len() < WRAPPED_FAILURE_POOL_SIZE {
-                        ffi::lua_rotate(state, 1, -1);
-                        ffi::lua_xmove(state, ref_thread, 1);
-                        let index = ref_stack_pop(extra);
-                        (*extra).wrapped_failure_pool.push(index);
-                    } else {
-                        ffi::lua_remove(state, 1);
-                    }
-                }
-                PreallocatedFailure::Existing(index) => {
-                    if (*extra).wrapped_failure_pool.len() < WRAPPED_FAILURE_POOL_SIZE {
-                        (*extra).wrapped_failure_pool.push(index);
-                    } else {
-                        ffi::lua_pushnil(ref_thread);
-                        ffi::lua_replace(ref_thread, index);
-                        (*extra).ref_free.push(index);
-                    }
+                    ffi::lua_rotate(state, 1, -1);
+                    ffi::lua_xmove(state, ref_thread, 1);
+                    let index = (*extra).ref_stack_pop();
+                    (*extra).wrapped_failure_pool.push(index);
+                    (*extra).wrapped_failure_top += 1;
                 }
+                PreallocatedFailure::Reserved => (*extra).wrapped_failure_top += 1,
             }
         }
     }
@@ -113,7 +102,11 @@ where
     // to store a wrapped failure (error or panic) *before* we proceed.
     let prealloc_failure = PreallocatedFailure::reserve(state, extra);
 
-    match catch_unwind(AssertUnwindSafe(|| f(extra, nargs))) {
+    match catch_unwind(AssertUnwindSafe(|| {
+        let rawlua = (*extra).raw_lua();
+        let _guard = StateGuard::new(rawlua, state);
+        f(extra, nargs)
+    })) {
         Ok(Ok(r)) => {
             // Return unused `WrappedFailure` to the pool
             prealloc_failure.release(state, extra);
@@ -122,6 +115,13 @@ where
         Ok(Err(err)) => {
             let wrapped_error = prealloc_failure.r#use(state, extra);
 
+            if !wrap_error {
+                ptr::write(wrapped_error, WrappedFailure::Error(err));
+                get_internal_metatable::<WrappedFailure>(state);
+                ffi::lua_setmetatable(state, -2);
+                ffi::lua_error(state)
+            }
+
             // Build `CallbackError` with traceback
             let traceback = if ffi::lua_checkstack(state, ffi::LUA_TRACEBACK_STACK) != 0 {
                 ffi::luaL_traceback(state, state, ptr::null(), 0);
@@ -150,31 +150,3 @@ where
         }
     }
 }
-
-pub(super) unsafe fn ref_stack_pop(extra: *mut ExtraData) -> c_int {
-    let extra = &mut *extra;
-    if let Some(free) = extra.ref_free.pop() {
-        ffi::lua_replace(extra.ref_thread, free);
-        return free;
-    }
-
-    // Try to grow max stack size
-    if extra.ref_stack_top >= extra.ref_stack_size {
-        let mut inc = extra.ref_stack_size; // Try to double stack size
-        while inc > 0 && ffi::lua_checkstack(extra.ref_thread, inc) == 0 {
-            inc /= 2;
-        }
-        if inc == 0 {
-            // Pop item on top of the stack to avoid stack leaking and successfully run destructors
-            // during unwinding.
-            ffi::lua_pop(extra.ref_thread, 1);
-            let top = extra.ref_stack_top;
-            // It is a user error to create enough references to exhaust the Lua max stack size for
-            // the ref thread.
-            panic!("cannot create a Lua reference, out of auxiliary stack space (used {top} slots)");
-        }
-        extra.ref_stack_size += inc;
-    }
-    extra.ref_stack_top += 1;
-    extra.ref_stack_top
-}

src/stdlib.rs

@@ -6,9 +6,11 @@ pub struct StdLib(u32);
 
 impl StdLib {
     /// [`coroutine`](https://www.lua.org/manual/5.4/manual.html#6.2) library
-    ///
-    /// Requires `feature = "lua54/lua53/lua52/luau"`
     #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52", feature = "luau"))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(any(feature = "lua54", feature = "lua53", feature = "lua52", feature = "luau")))
+    )]
     pub const COROUTINE: StdLib = StdLib(1);
 
     /// [`table`](https://www.lua.org/manual/5.4/manual.html#6.6) library
@@ -26,38 +28,42 @@ impl StdLib {
     pub const STRING: StdLib = StdLib(1 << 4);
 
     /// [`utf8`](https://www.lua.org/manual/5.4/manual.html#6.5) library
-    ///
-    /// Requires `feature = "lua54/lua53/luau"`
     #[cfg(any(feature = "lua54", feature = "lua53", feature = "luau"))]
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "lua54", feature = "lua53", feature = "luau"))))]
     pub const UTF8: StdLib = StdLib(1 << 5);
 
     /// [`bit`](https://www.lua.org/manual/5.2/manual.html#6.7) library
-    ///
-    /// Requires `feature = "lua52/luajit/luau"`
     #[cfg(any(feature = "lua52", feature = "luajit", feature = "luau", doc))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(any(feature = "lua52", feature = "luajit", feature = "luau")))
+    )]
     pub const BIT: StdLib = StdLib(1 << 6);
 
     /// [`math`](https://www.lua.org/manual/5.4/manual.html#6.7) library
     pub const MATH: StdLib = StdLib(1 << 7);
 
     /// [`package`](https://www.lua.org/manual/5.4/manual.html#6.3) library
+    #[cfg(not(feature = "luau"))]
+    #[cfg_attr(docsrs, doc(cfg(not(feature = "luau"))))]
     pub const PACKAGE: StdLib = StdLib(1 << 8);
 
-    /// [`buffer`](https://luau-lang.org/library#buffer-library) library
+    /// [`buffer`](https://luau.org/library#buffer-library) library
     #[cfg(any(feature = "luau", doc))]
     #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
     pub const BUFFER: StdLib = StdLib(1 << 9);
 
+    /// [`vector`](https://luau.org/library#vector-library) library
+    #[cfg(any(feature = "luau", doc))]
+    #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
+    pub const VECTOR: StdLib = StdLib(1 << 10);
+
     /// [`jit`](http://luajit.org/ext_jit.html) library
-    ///
-    /// Requires `feature = "luajit"`
     #[cfg(any(feature = "luajit", doc))]
     #[cfg_attr(docsrs, doc(cfg(feature = "luajit")))]
-    pub const JIT: StdLib = StdLib(1 << 9);
+    pub const JIT: StdLib = StdLib(1 << 11);
 
     /// (**unsafe**) [`ffi`](http://luajit.org/ext_ffi.html) library
-    ///
-    /// Requires `feature = "luajit"`
     #[cfg(any(feature = "luajit", doc))]
     #[cfg_attr(docsrs, doc(cfg(feature = "luajit")))]
     pub const FFI: StdLib = StdLib(1 << 30);

src/string.rs

@@ -1,20 +1,22 @@
-use std::borrow::Borrow;
+use std::borrow::{Borrow, Cow};
 use std::hash::{Hash, Hasher};
 use std::ops::Deref;
-use std::os::raw::c_void;
+use std::os::raw::{c_int, c_void};
 use std::string::String as StdString;
 use std::{cmp, fmt, slice, str};
 
-#[cfg(feature = "serialize")]
+use crate::error::{Error, Result};
+use crate::state::Lua;
+use crate::traits::IntoLua;
+use crate::types::{LuaType, ValueRef};
+use crate::value::Value;
+
+#[cfg(feature = "serde")]
 use {
     serde::ser::{Serialize, Serializer},
     std::result::Result as StdResult,
 };
 
-use crate::error::{Error, Result};
-use crate::state::Lua;
-use crate::types::ValueRef;
-
 /// Handle to an internal Lua string.
 ///
 /// Unlike Rust strings, Lua strings may not be valid UTF-8.
@@ -41,21 +43,19 @@ impl String {
     /// # }
     /// ```
     #[inline]
-    pub fn to_str(&self) -> Result<BorrowedStr> {
-        let BorrowedBytes(bytes, guard) = self.as_bytes();
-        let s = str::from_utf8(bytes).map_err(|e| Error::FromLuaConversionError {
-            from: "string",
-            to: "&str",
-            message: Some(e.to_string()),
-        })?;
-        Ok(BorrowedStr(s, guard))
+    pub fn to_str(&self) -> Result<BorrowedStr<'_>> {
+        BorrowedStr::try_from(self)
     }
 
     /// Converts this string to a [`StdString`].
     ///
     /// Any non-Unicode sequences are replaced with [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD].
     ///
+    /// This method returns [`StdString`] instead of [`Cow<'_, str>`] because lifetime cannot be
+    /// bound to a weak Lua object.
+    ///
     /// [U+FFFD]: std::char::REPLACEMENT_CHARACTER
+    /// [`Cow<'_, str>`]: std::borrow::Cow
     ///
     /// # Examples
     ///
@@ -74,9 +74,19 @@ impl String {
         StdString::from_utf8_lossy(&self.as_bytes()).into_owned()
     }
 
+    /// Returns an object that implements [`Display`] for safely printing a Lua [`String`] that may
+    /// contain non-Unicode data.
+    ///
+    /// This may perform lossy conversion.
+    ///
+    /// [`Display`]: fmt::Display
+    pub fn display(&self) -> impl fmt::Display + '_ {
+        Display(self)
+    }
+
     /// Get the bytes that make up this string.
     ///
-    /// The returned slice will not contain the terminating nul byte, but will contain any nul
+    /// The returned slice will not contain the terminating null byte, but will contain any null
     /// bytes embedded into the Lua string.
     ///
     /// # Examples
@@ -92,35 +102,37 @@ impl String {
     /// # }
     /// ```
     #[inline]
-    pub fn as_bytes(&self) -> BorrowedBytes {
-        let (bytes, guard) = unsafe { self.to_slice() };
-        BorrowedBytes(&bytes[..bytes.len() - 1], guard)
+    pub fn as_bytes(&self) -> BorrowedBytes<'_> {
+        BorrowedBytes::from(self)
     }
 
-    /// Get the bytes that make up this string, including the trailing nul byte.
-    pub fn as_bytes_with_nul(&self) -> BorrowedBytes {
-        let (bytes, guard) = unsafe { self.to_slice() };
-        BorrowedBytes(bytes, guard)
+    /// Get the bytes that make up this string, including the trailing null byte.
+    pub fn as_bytes_with_nul(&self) -> BorrowedBytes<'_> {
+        let BorrowedBytes { buf, borrow, _lua } = BorrowedBytes::from(self);
+        // Include the trailing null byte (it's always present but excluded by default)
+        let buf = unsafe { slice::from_raw_parts((*buf).as_ptr(), (*buf).len() + 1) };
+        BorrowedBytes { buf, borrow, _lua }
     }
 
+    // Does not return the terminating null byte
     unsafe fn to_slice(&self) -> (&[u8], Lua) {
         let lua = self.0.lua.upgrade();
-        let rawlua = lua.lock();
-        let ref_thread = rawlua.ref_thread();
-        unsafe {
+        let slice = {
+            let rawlua = lua.lock();
+            let ref_thread = rawlua.ref_thread();
+
             mlua_debug_assert!(
                 ffi::lua_type(ref_thread, self.0.index) == ffi::LUA_TSTRING,
                 "string ref is not string type"
             );
 
-            let mut size = 0;
             // This will not trigger a 'm' error, because the reference is guaranteed to be of
             // string type
+            let mut size = 0;
             let data = ffi::lua_tolstring(ref_thread, self.0.index, &mut size);
-
-            drop(rawlua);
-            (slice::from_raw_parts(data as *const u8, size + 1), lua)
-        }
+            slice::from_raw_parts(data as *const u8, size)
+        };
+        (slice, lua)
     }
 
     /// Converts this string to a generic C pointer.
@@ -143,27 +155,12 @@ impl fmt::Debug for String {
         }
 
         // Format as bytes
-        write!(f, "b\"")?;
-        for &b in bytes {
-            // https://doc.rust-lang.org/reference/tokens.html#byte-escapes
-            match b {
-                b'\n' => write!(f, "\\n")?,
-                b'\r' => write!(f, "\\r")?,
-                b'\t' => write!(f, "\\t")?,
-                b'\\' | b'"' => write!(f, "\\{}", b as char)?,
-                b'\0' => write!(f, "\\0")?,
-                // ASCII printable
-                0x20..=0x7e => write!(f, "{}", b as char)?,
-                _ => write!(f, "\\x{b:02x}")?,
-            }
-        }
-        write!(f, "\"")?;
-
-        Ok(())
+        write!(f, "b")?;
+        <bstr::BStr as fmt::Debug>::fmt(bstr::BStr::new(&bytes), f)
     }
 }
 
-// Lua strings are basically &[u8] slices, so implement PartialEq for anything resembling that.
+// Lua strings are basically `&[u8]` slices, so implement `PartialEq` for anything resembling that.
 //
 // This makes our `String` comparable with `Vec<u8>`, `[u8]`, `&str` and `String`.
 //
@@ -179,19 +176,34 @@ where
     }
 }
 
-impl PartialEq<String> for String {
+impl PartialEq for String {
     fn eq(&self, other: &String) -> bool {
         self.as_bytes() == other.as_bytes()
     }
 }
 
-impl PartialEq<&String> for String {
-    fn eq(&self, other: &&String) -> bool {
-        self.as_bytes() == other.as_bytes()
+impl Eq for String {}
+
+impl<T> PartialOrd<T> for String
+where
+    T: AsRef<[u8]> + ?Sized,
+{
+    fn partial_cmp(&self, other: &T) -> Option<cmp::Ordering> {
+        self.as_bytes().partial_cmp(&other.as_ref())
     }
 }
 
-impl Eq for String {}
+impl PartialOrd for String {
+    fn partial_cmp(&self, other: &String) -> Option<cmp::Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for String {
+    fn cmp(&self, other: &String) -> cmp::Ordering {
+        self.as_bytes().cmp(&other.as_bytes())
+    }
+}
 
 impl Hash for String {
     fn hash<H: Hasher>(&self, state: &mut H) {
@@ -199,7 +211,7 @@ impl Hash for String {
     }
 }
 
-#[cfg(feature = "serialize")]
+#[cfg(feature = "serde")]
 impl Serialize for String {
     fn serialize<S>(&self, serializer: S) -> StdResult<S::Ok, S::Error>
     where
@@ -212,41 +224,55 @@ impl Serialize for String {
     }
 }
 
+struct Display<'a>(&'a String);
+
+impl fmt::Display for Display<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let bytes = self.0.as_bytes();
+        <bstr::BStr as fmt::Display>::fmt(bstr::BStr::new(&bytes), f)
+    }
+}
+
 /// A borrowed string (`&str`) that holds a strong reference to the Lua state.
-pub struct BorrowedStr<'a>(&'a str, #[allow(unused)] Lua);
+pub struct BorrowedStr<'a> {
+    // `buf` points to a readonly memory managed by Lua
+    pub(crate) buf: &'a str,
+    pub(crate) borrow: Cow<'a, String>,
+    pub(crate) _lua: Lua,
+}
 
 impl Deref for BorrowedStr<'_> {
     type Target = str;
 
     #[inline(always)]
     fn deref(&self) -> &str {
-        self.0
+        self.buf
     }
 }
 
 impl Borrow<str> for BorrowedStr<'_> {
     #[inline(always)]
     fn borrow(&self) -> &str {
-        self.0
+        self.buf
     }
 }
 
 impl AsRef<str> for BorrowedStr<'_> {
     #[inline(always)]
     fn as_ref(&self) -> &str {
-        self.0
+        self.buf
     }
 }
 
 impl fmt::Display for BorrowedStr<'_> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        self.0.fmt(f)
+        self.buf.fmt(f)
     }
 }
 
 impl fmt::Debug for BorrowedStr<'_> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        self.0.fmt(f)
+        self.buf.fmt(f)
     }
 }
 
@@ -255,48 +281,76 @@ where
     T: AsRef<str>,
 {
     fn eq(&self, other: &T) -> bool {
-        self.0 == other.as_ref()
+        self.buf == other.as_ref()
     }
 }
 
+impl Eq for BorrowedStr<'_> {}
+
 impl<T> PartialOrd<T> for BorrowedStr<'_>
 where
     T: AsRef<str>,
 {
     fn partial_cmp(&self, other: &T) -> Option<cmp::Ordering> {
-        self.0.partial_cmp(other.as_ref())
+        self.buf.partial_cmp(other.as_ref())
+    }
+}
+
+impl Ord for BorrowedStr<'_> {
+    fn cmp(&self, other: &Self) -> cmp::Ordering {
+        self.buf.cmp(other.buf)
+    }
+}
+
+impl<'a> TryFrom<&'a String> for BorrowedStr<'a> {
+    type Error = Error;
+
+    #[inline]
+    fn try_from(value: &'a String) -> Result<Self> {
+        let BorrowedBytes { buf, borrow, _lua } = BorrowedBytes::from(value);
+        let buf = str::from_utf8(buf).map_err(|e| Error::FromLuaConversionError {
+            from: "string",
+            to: "&str".to_string(),
+            message: Some(e.to_string()),
+        })?;
+        Ok(Self { buf, borrow, _lua })
     }
 }
 
 /// A borrowed byte slice (`&[u8]`) that holds a strong reference to the Lua state.
-pub struct BorrowedBytes<'a>(&'a [u8], #[allow(unused)] Lua);
+pub struct BorrowedBytes<'a> {
+    // `buf` points to a readonly memory managed by Lua
+    pub(crate) buf: &'a [u8],
+    pub(crate) borrow: Cow<'a, String>,
+    pub(crate) _lua: Lua,
+}
 
 impl Deref for BorrowedBytes<'_> {
     type Target = [u8];
 
     #[inline(always)]
     fn deref(&self) -> &[u8] {
-        self.0
+        self.buf
     }
 }
 
 impl Borrow<[u8]> for BorrowedBytes<'_> {
     #[inline(always)]
     fn borrow(&self) -> &[u8] {
-        self.0
+        self.buf
     }
 }
 
 impl AsRef<[u8]> for BorrowedBytes<'_> {
     #[inline(always)]
     fn as_ref(&self) -> &[u8] {
-        self.0
+        self.buf
     }
 }
 
 impl fmt::Debug for BorrowedBytes<'_> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        self.0.fmt(f)
+        self.buf.fmt(f)
     }
 }
 
@@ -305,28 +359,66 @@ where
     T: AsRef<[u8]>,
 {
     fn eq(&self, other: &T) -> bool {
-        self.0 == other.as_ref()
+        self.buf == other.as_ref()
     }
 }
 
+impl Eq for BorrowedBytes<'_> {}
+
 impl<T> PartialOrd<T> for BorrowedBytes<'_>
 where
     T: AsRef<[u8]>,
 {
     fn partial_cmp(&self, other: &T) -> Option<cmp::Ordering> {
-        self.0.partial_cmp(other.as_ref())
+        self.buf.partial_cmp(other.as_ref())
     }
 }
 
-impl<'a> IntoIterator for BorrowedBytes<'a> {
+impl Ord for BorrowedBytes<'_> {
+    fn cmp(&self, other: &Self) -> cmp::Ordering {
+        self.buf.cmp(other.buf)
+    }
+}
+
+impl<'a> IntoIterator for &'a BorrowedBytes<'_> {
     type Item = &'a u8;
     type IntoIter = slice::Iter<'a, u8>;
 
     fn into_iter(self) -> Self::IntoIter {
-        self.0.iter()
+        self.iter()
     }
 }
 
+impl<'a> From<&'a String> for BorrowedBytes<'a> {
+    #[inline]
+    fn from(value: &'a String) -> Self {
+        let (buf, _lua) = unsafe { value.to_slice() };
+        let borrow = Cow::Borrowed(value);
+        Self { buf, borrow, _lua }
+    }
+}
+
+struct WrappedString<T: AsRef<[u8]>>(T);
+
+impl String {
+    /// Wraps bytes, returning an opaque type that implements [`IntoLua`] trait.
+    ///
+    /// This function uses [`Lua::create_string`] under the hood.
+    pub fn wrap(data: impl AsRef<[u8]>) -> impl IntoLua {
+        WrappedString(data)
+    }
+}
+
+impl<T: AsRef<[u8]>> IntoLua for WrappedString<T> {
+    fn into_lua(self, lua: &Lua) -> Result<Value> {
+        lua.create_string(self.0).map(Value::String)
+    }
+}
+
+impl LuaType for String {
+    const TYPE_ID: c_int = ffi::LUA_TSTRING;
+}
+
 #[cfg(test)]
 mod assertions {
     use super::*;

src/table.rs

@@ -1,29 +1,29 @@
 use std::collections::HashSet;
 use std::fmt;
 use std::marker::PhantomData;
-use std::os::raw::c_void;
+use std::os::raw::{c_int, c_void};
 use std::string::String as StdString;
 
-#[cfg(feature = "serialize")]
+use crate::error::{Error, Result};
+use crate::function::Function;
+use crate::state::{LuaGuard, RawLua};
+use crate::traits::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, ObjectLike};
+use crate::types::{Integer, LuaType, ValueRef};
+use crate::util::{assert_stack, check_stack, get_metatable_ptr, StackGuard};
+use crate::value::{Nil, Value};
+
+#[cfg(feature = "async")]
+use crate::function::AsyncCallFuture;
+
+#[cfg(feature = "serde")]
 use {
     rustc_hash::FxHashSet,
     serde::ser::{Serialize, SerializeMap, SerializeSeq, Serializer},
     std::{cell::RefCell, rc::Rc, result::Result as StdResult},
 };
 
-use crate::error::{Error, Result};
-use crate::function::Function;
-use crate::state::{LuaGuard, RawLua};
-use crate::traits::ObjectLike;
-use crate::types::{Integer, ValueRef};
-use crate::util::{assert_stack, check_stack, StackGuard};
-use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, Nil, Value};
-
-#[cfg(feature = "async")]
-use futures_util::future::{self, Either, Future};
-
 /// Handle to an internal Lua table.
-#[derive(Clone)]
+#[derive(Clone, PartialEq)]
 pub struct Table(pub(crate) ValueRef);
 
 impl Table {
@@ -59,7 +59,7 @@ impl Table {
     /// # }
     /// ```
     ///
-    /// [`raw_set`]: #method.raw_set
+    /// [`raw_set`]: Table::raw_set
     pub fn set(&self, key: impl IntoLua, value: impl IntoLua) -> Result<()> {
         // Fast track (skip protected call)
         if !self.has_metatable() {
@@ -106,7 +106,7 @@ impl Table {
     /// # }
     /// ```
     ///
-    /// [`raw_get`]: #method.raw_get
+    /// [`raw_get`]: Table::raw_get
     pub fn get<V: FromLua>(&self, key: impl IntoLua) -> Result<V> {
         // Fast track (skip protected call)
         if !self.has_metatable() {
@@ -211,28 +211,27 @@ impl Table {
     ///
     /// let always_equals_mt = lua.create_table()?;
     /// always_equals_mt.set("__eq", lua.create_function(|_, (_t1, _t2): (Table, Table)| Ok(true))?)?;
-    /// table2.set_metatable(Some(always_equals_mt));
+    /// table2.set_metatable(Some(always_equals_mt))?;
     ///
     /// assert!(table1.equals(&table1.clone())?);
     /// assert!(table1.equals(&table2)?);
     /// # Ok(())
     /// # }
     /// ```
-    pub fn equals<T: AsRef<Self>>(&self, other: T) -> Result<bool> {
-        let other = other.as_ref();
+    pub fn equals(&self, other: &Self) -> Result<bool> {
         if self == other {
             return Ok(true);
         }
 
-        // Compare using __eq metamethod if exists
+        // Compare using `__eq` metamethod if exists
         // First, check the self for the metamethod.
         // If self does not define it, then check the other table.
-        if let Some(mt) = self.get_metatable() {
+        if let Some(mt) = self.metatable() {
             if mt.contains_key("__eq")? {
                 return mt.get::<Function>("__eq")?.call((self, other));
             }
         }
-        if let Some(mt) = other.get_metatable() {
+        if let Some(mt) = other.metatable() {
             if mt.contains_key("__eq")? {
                 return mt.get::<Function>("__eq")?.call((self, other));
             }
@@ -243,12 +242,12 @@ impl Table {
 
     /// Sets a key-value pair without invoking metamethods.
     pub fn raw_set(&self, key: impl IntoLua, value: impl IntoLua) -> Result<()> {
-        #[cfg(feature = "luau")]
-        self.check_readonly_write()?;
-
         let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
+            #[cfg(feature = "luau")]
+            self.check_readonly_write(&lua)?;
+
             let _sg = StackGuard::new(state);
             check_stack(state, 5)?;
 
@@ -283,7 +282,9 @@ impl Table {
     }
 
     /// Inserts element value at position `idx` to the table, shifting up the elements from
-    /// `table[idx]`. The worst case complexity is O(n), where n is the table length.
+    /// `table[idx]`.
+    ///
+    /// The worst case complexity is O(n), where n is the table length.
     pub fn raw_insert(&self, idx: Integer, value: impl IntoLua) -> Result<()> {
         let size = self.raw_len() as Integer;
         if idx < 1 || idx > size + 1 {
@@ -311,12 +312,12 @@ impl Table {
 
     /// Appends a value to the back of the table without invoking metamethods.
     pub fn raw_push(&self, value: impl IntoLua) -> Result<()> {
-        #[cfg(feature = "luau")]
-        self.check_readonly_write()?;
-
         let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
+            #[cfg(feature = "luau")]
+            self.check_readonly_write(&lua)?;
+
             let _sg = StackGuard::new(state);
             check_stack(state, 4)?;
 
@@ -339,12 +340,12 @@ impl Table {
 
     /// Removes the last element from the table and returns it, without invoking metamethods.
     pub fn raw_pop<V: FromLua>(&self) -> Result<V> {
-        #[cfg(feature = "luau")]
-        self.check_readonly_write()?;
-
         let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
+            #[cfg(feature = "luau")]
+            self.check_readonly_write(&lua)?;
+
             let _sg = StackGuard::new(state);
             check_stack(state, 3)?;
 
@@ -362,8 +363,8 @@ impl Table {
     /// Removes a key from the table.
     ///
     /// If `key` is an integer, mlua shifts down the elements from `table[key+1]`,
-    /// and erases element `table[key]`. The complexity is O(n) in the worst case,
-    /// where n is the table length.
+    /// and erases element `table[key]`. The complexity is `O(n)` in the worst case,
+    /// where `n` is the table length.
     ///
     /// For other key types this is equivalent to setting `table[key] = nil`.
     pub fn raw_remove(&self, key: impl IntoLua) -> Result<()> {
@@ -400,13 +401,13 @@ impl Table {
     ///
     /// This method is useful to clear the table while keeping its capacity.
     pub fn clear(&self) -> Result<()> {
-        #[cfg(feature = "luau")]
-        self.check_readonly_write()?;
-
         let lua = self.0.lua.lock();
         unsafe {
             #[cfg(feature = "luau")]
-            ffi::lua_cleartable(lua.ref_thread(), self.0.index);
+            {
+                self.check_readonly_write(&lua)?;
+                ffi::lua_cleartable(lua.ref_thread(), self.0.index);
+            }
 
             #[cfg(not(feature = "luau"))]
             {
@@ -438,9 +439,8 @@ impl Table {
 
     /// Returns the result of the Lua `#` operator.
     ///
-    /// This might invoke the `__len` metamethod. Use the [`raw_len`] method if that is not desired.
-    ///
-    /// [`raw_len`]: #method.raw_len
+    /// This might invoke the `__len` metamethod. Use the [`Table::raw_len`] method if that is not
+    /// desired.
     pub fn len(&self) -> Result<Integer> {
         // Fast track (skip protected call)
         if !self.has_metatable() {
@@ -468,43 +468,31 @@ impl Table {
     ///
     /// It checks both the array part and the hash part.
     pub fn is_empty(&self) -> bool {
-        // Check array part
-        if self.raw_len() != 0 {
-            return false;
-        }
-
-        // Check hash part
         let lua = self.0.lua.lock();
-        let state = lua.state();
+        let ref_thread = lua.ref_thread();
         unsafe {
-            let _sg = StackGuard::new(state);
-            assert_stack(state, 4);
-
-            lua.push_ref(&self.0);
-            ffi::lua_pushnil(state);
-            if ffi::lua_next(state, -2) != 0 {
-                return false;
+            ffi::lua_pushnil(ref_thread);
+            if ffi::lua_next(ref_thread, self.0.index) == 0 {
+                return true;
             }
+            ffi::lua_pop(ref_thread, 2);
         }
-
-        true
+        false
     }
 
     /// Returns a reference to the metatable of this table, or `None` if no metatable is set.
     ///
-    /// Unlike the `getmetatable` Lua function, this method ignores the `__metatable` field.
-    pub fn get_metatable(&self) -> Option<Table> {
+    /// Unlike the [`getmetatable`] Lua function, this method ignores the `__metatable` field.
+    ///
+    /// [`getmetatable`]: https://www.lua.org/manual/5.4/manual.html#pdf-getmetatable
+    pub fn metatable(&self) -> Option<Table> {
         let lua = self.0.lua.lock();
-        let state = lua.state();
+        let ref_thread = lua.ref_thread();
         unsafe {
-            let _sg = StackGuard::new(state);
-            assert_stack(state, 2);
-
-            lua.push_ref(&self.0);
-            if ffi::lua_getmetatable(state, -1) == 0 {
+            if ffi::lua_getmetatable(ref_thread, self.0.index) == 0 {
                 None
             } else {
-                Some(Table(lua.pop_ref()))
+                Some(Table(lua.pop_ref_thread()))
             }
         }
     }
@@ -513,27 +501,23 @@ impl Table {
     ///
     /// If `metatable` is `None`, the metatable is removed (if no metatable is set, this does
     /// nothing).
-    pub fn set_metatable(&self, metatable: Option<Table>) {
-        // Workaround to throw readonly error without returning Result
+    pub fn set_metatable(&self, metatable: Option<Table>) -> Result<()> {
         #[cfg(feature = "luau")]
         if self.is_readonly() {
-            panic!("attempt to modify a readonly table");
+            return Err(Error::runtime("attempt to modify a readonly table"));
         }
 
         let lua = self.0.lua.lock();
-        let state = lua.state();
+        let ref_thread = lua.ref_thread();
         unsafe {
-            let _sg = StackGuard::new(state);
-            assert_stack(state, 2);
-
-            lua.push_ref(&self.0);
             if let Some(metatable) = metatable {
-                lua.push_ref(&metatable.0);
+                ffi::lua_pushvalue(ref_thread, metatable.0.index);
             } else {
-                ffi::lua_pushnil(state);
+                ffi::lua_pushnil(ref_thread);
             }
-            ffi::lua_setmetatable(state, -2);
+            ffi::lua_setmetatable(ref_thread, self.0.index);
         }
+        Ok(())
     }
 
     /// Returns true if the table has metatable attached.
@@ -541,19 +525,10 @@ impl Table {
     #[inline]
     pub fn has_metatable(&self) -> bool {
         let lua = self.0.lua.lock();
-        let ref_thread = lua.ref_thread();
-        unsafe {
-            if ffi::lua_getmetatable(ref_thread, self.0.index) != 0 {
-                ffi::lua_pop(ref_thread, 1);
-                return true;
-            }
-        }
-        false
+        unsafe { !get_metatable_ptr(lua.ref_thread(), self.0.index).is_null() }
     }
 
     /// Sets `readonly` attribute on the table.
-    ///
-    /// Requires `feature = "luau"`
     #[cfg(any(feature = "luau", doc))]
     #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
     pub fn set_readonly(&self, enabled: bool) {
@@ -569,8 +544,6 @@ impl Table {
     }
 
     /// Returns `readonly` attribute of the table.
-    ///
-    /// Requires `feature = "luau"`
     #[cfg(any(feature = "luau", doc))]
     #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
     pub fn is_readonly(&self) -> bool {
@@ -579,6 +552,22 @@ impl Table {
         unsafe { ffi::lua_getreadonly(ref_thread, self.0.index) != 0 }
     }
 
+    /// Controls `safeenv` attribute on the table.
+    ///
+    /// This a special flag that activates some performance optimizations for environment tables.
+    /// In particular, it controls:
+    /// - Optimization of import resolution (cache values of constant keys).
+    /// - Fast-path for built-in iteration with pairs/ipairs.
+    /// - Fast-path for some built-in functions (fastcall).
+    ///
+    /// For `safeenv` environments, monkey patching or modifying values may not work as expected.
+    #[cfg(any(feature = "luau", doc))]
+    #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
+    pub fn set_safeenv(&self, enabled: bool) {
+        let lua = self.0.lua.lock();
+        unsafe { ffi::lua_setsafeenv(lua.ref_thread(), self.0.index, enabled as _) };
+    }
+
     /// Converts this table to a generic C pointer.
     ///
     /// Different tables will give different pointers.
@@ -615,9 +604,8 @@ impl Table {
     /// # }
     /// ```
     ///
-    /// [`Result`]: crate::Result
     /// [Lua manual]: http://www.lua.org/manual/5.4/manual.html#pdf-next
-    pub fn pairs<K: FromLua, V: FromLua>(&self) -> TablePairs<K, V> {
+    pub fn pairs<K: FromLua, V: FromLua>(&self) -> TablePairs<'_, K, V> {
         TablePairs {
             guard: self.0.lua.lock(),
             table: self,
@@ -682,11 +670,7 @@ impl Table {
     /// # Ok(())
     /// # }
     /// ```
-    ///
-    /// [`pairs`]: #method.pairs
-    /// [`Result`]: crate::Result
-    /// [Lua manual]: http://www.lua.org/manual/5.4/manual.html#pdf-next
-    pub fn sequence_values<V: FromLua>(&self) -> TableSequence<V> {
+    pub fn sequence_values<V: FromLua>(&self) -> TableSequence<'_, V> {
         TableSequence {
             guard: self.0.lua.lock(),
             table: self,
@@ -695,8 +679,9 @@ impl Table {
         }
     }
 
-    #[cfg(feature = "serialize")]
-    pub(crate) fn for_each_value<V>(&self, mut f: impl FnMut(V) -> Result<()>) -> Result<()>
+    /// Iterates over the sequence part of the table, invoking the given closure on each value.
+    #[doc(hidden)]
+    pub fn for_each_value<V>(&self, mut f: impl FnMut(V) -> Result<()>) -> Result<()>
     where
         V: FromLua,
     {
@@ -720,12 +705,12 @@ impl Table {
     /// Sets element value at position `idx` without invoking metamethods.
     #[doc(hidden)]
     pub fn raw_seti(&self, idx: usize, value: impl IntoLua) -> Result<()> {
-        #[cfg(feature = "luau")]
-        self.check_readonly_write()?;
-
         let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
+            #[cfg(feature = "luau")]
+            self.check_readonly_write(&lua)?;
+
             let _sg = StackGuard::new(state);
             check_stack(state, 5)?;
 
@@ -742,7 +727,7 @@ impl Table {
         Ok(())
     }
 
-    #[cfg(feature = "serialize")]
+    #[cfg(feature = "serde")]
     pub(crate) fn is_array(&self) -> bool {
         let lua = self.0.lua.lock();
         let state = lua.state();
@@ -761,8 +746,8 @@ impl Table {
 
     #[cfg(feature = "luau")]
     #[inline(always)]
-    pub(crate) fn check_readonly_write(&self) -> Result<()> {
-        if self.is_readonly() {
+    fn check_readonly_write(&self, lua: &RawLua) -> Result<()> {
+        if unsafe { ffi::lua_getreadonly(lua.ref_thread(), self.0.index) != 0 } {
             return Err(Error::runtime("attempt to modify a readonly table"));
         }
         Ok(())
@@ -779,17 +764,41 @@ impl Table {
         // Collect key/value pairs into a vector so we can sort them
         let mut pairs = self.pairs::<Value, Value>().flatten().collect::<Vec<_>>();
         // Sort keys
-        pairs.sort_by(|(a, _), (b, _)| a.cmp(b));
+        pairs.sort_by(|(a, _), (b, _)| a.sort_cmp(b));
+        let is_sequence = (pairs.iter().enumerate())
+            .all(|(i, (k, _))| matches!(k, Value::Integer(n) if *n == (i + 1) as Integer));
         if pairs.is_empty() {
             return write!(fmt, "{{}}");
         }
         writeln!(fmt, "{{")?;
-        for (key, value) in pairs {
-            write!(fmt, "{}[", " ".repeat(ident + 2))?;
-            key.fmt_pretty(fmt, false, ident + 2, visited)?;
-            write!(fmt, "] = ")?;
-            value.fmt_pretty(fmt, true, ident + 2, visited)?;
-            writeln!(fmt, ",")?;
+        if is_sequence {
+            // Format as list
+            for (_, value) in pairs {
+                write!(fmt, "{}", " ".repeat(ident + 2))?;
+                value.fmt_pretty(fmt, true, ident + 2, visited)?;
+                writeln!(fmt, ",")?;
+            }
+        } else {
+            fn is_simple_key(key: &[u8]) -> bool {
+                key.iter().take(1).all(|c| c.is_ascii_alphabetic() || *c == b'_')
+                    && key.iter().all(|c| c.is_ascii_alphanumeric() || *c == b'_')
+            }
+
+            for (key, value) in pairs {
+                match key {
+                    Value::String(key) if is_simple_key(&key.as_bytes()) => {
+                        write!(fmt, "{}{}", " ".repeat(ident + 2), key.display())?;
+                        write!(fmt, " = ")?;
+                    }
+                    _ => {
+                        write!(fmt, "{}[", " ".repeat(ident + 2))?;
+                        key.fmt_pretty(fmt, false, ident + 2, visited)?;
+                        write!(fmt, "] = ")?;
+                    }
+                }
+                value.fmt_pretty(fmt, true, ident + 2, visited)?;
+                writeln!(fmt, ",")?;
+            }
         }
         write!(fmt, "{}}}", " ".repeat(ident))
     }
@@ -800,20 +809,7 @@ impl fmt::Debug for Table {
         if fmt.alternate() {
             return self.fmt_pretty(fmt, 0, &mut HashSet::new());
         }
-        fmt.write_fmt(format_args!("Table({:?})", self.0))
-    }
-}
-
-impl PartialEq for Table {
-    fn eq(&self, other: &Self) -> bool {
-        self.0 == other.0
-    }
-}
-
-impl AsRef<Table> for Table {
-    #[inline]
-    fn as_ref(&self) -> &Self {
-        self
+        fmt.debug_tuple("Table").field(&self.0).finish()
     }
 }
 
@@ -867,6 +863,10 @@ where
     }
 }
 
+impl LuaType for Table {
+    const TYPE_ID: c_int = ffi::LUA_TTABLE;
+}
+
 impl ObjectLike for Table {
     #[inline]
     fn get<V: FromLua>(&self, key: impl IntoLua) -> Result<V> {
@@ -889,7 +889,7 @@ impl ObjectLike for Table {
 
     #[cfg(feature = "async")]
     #[inline]
-    fn call_async<R>(&self, args: impl IntoLuaMulti) -> impl Future<Output = Result<R>>
+    fn call_async<R>(&self, args: impl IntoLuaMulti) -> AsyncCallFuture<R>
     where
         R: FromLuaMulti,
     {
@@ -905,7 +905,7 @@ impl ObjectLike for Table {
     }
 
     #[cfg(feature = "async")]
-    fn call_async_method<R>(&self, name: &str, args: impl IntoLuaMulti) -> impl Future<Output = Result<R>>
+    fn call_async_method<R>(&self, name: &str, args: impl IntoLuaMulti) -> AsyncCallFuture<R>
     where
         R: FromLuaMulti,
     {
@@ -925,17 +925,17 @@ impl ObjectLike for Table {
 
     #[cfg(feature = "async")]
     #[inline]
-    fn call_async_function<R>(&self, name: &str, args: impl IntoLuaMulti) -> impl Future<Output = Result<R>>
+    fn call_async_function<R>(&self, name: &str, args: impl IntoLuaMulti) -> AsyncCallFuture<R>
     where
         R: FromLuaMulti,
     {
         match self.get(name) {
-            Ok(Value::Function(func)) => Either::Left(func.call_async(args)),
+            Ok(Value::Function(func)) => func.call_async(args),
             Ok(val) => {
                 let msg = format!("attempt to call a {} value (function '{name}')", val.type_name());
-                Either::Right(future::ready(Err(Error::RuntimeError(msg))))
+                AsyncCallFuture::error(Error::RuntimeError(msg))
             }
-            Err(err) => Either::Right(future::ready(Err(err))),
+            Err(err) => AsyncCallFuture::error(err),
         }
     }
 
@@ -946,14 +946,14 @@ impl ObjectLike for Table {
 }
 
 /// A wrapped [`Table`] with customized serialization behavior.
-#[cfg(feature = "serialize")]
+#[cfg(feature = "serde")]
 pub(crate) struct SerializableTable<'a> {
     table: &'a Table,
     options: crate::serde::de::Options,
     visited: Rc<RefCell<FxHashSet<*const c_void>>>,
 }
 
-#[cfg(feature = "serialize")]
+#[cfg(feature = "serde")]
 impl Serialize for Table {
     #[inline]
     fn serialize<S: Serializer>(&self, serializer: S) -> StdResult<S::Ok, S::Error> {
@@ -961,7 +961,7 @@ impl Serialize for Table {
     }
 }
 
-#[cfg(feature = "serialize")]
+#[cfg(feature = "serde")]
 impl<'a> SerializableTable<'a> {
     #[inline]
     pub(crate) fn new(
@@ -977,8 +977,8 @@ impl<'a> SerializableTable<'a> {
     }
 }
 
-#[cfg(feature = "serialize")]
-impl<'a> Serialize for SerializableTable<'a> {
+#[cfg(feature = "serde")]
+impl Serialize for SerializableTable<'_> {
     fn serialize<S>(&self, serializer: S) -> StdResult<S::Ok, S::Error>
     where
         S: Serializer,
@@ -999,7 +999,10 @@ impl<'a> Serialize for SerializableTable<'a> {
 
         // Array
         let len = self.table.raw_len();
-        if len > 0 || self.table.is_array() {
+        if len > 0
+            || self.table.is_array()
+            || (self.options.encode_empty_tables_as_array && self.table.is_empty())
+        {
             let mut seq = serializer.serialize_seq(Some(len))?;
             let mut serialize_err = None;
             let res = self.table.for_each_value::<Value>(|value| {
@@ -1069,7 +1072,7 @@ pub struct TablePairs<'a, K, V> {
     _phantom: PhantomData<(K, V)>,
 }
 
-impl<'a, K, V> Iterator for TablePairs<'a, K, V>
+impl<K, V> Iterator for TablePairs<'_, K, V>
 where
     K: FromLua,
     V: FromLua,
@@ -1129,7 +1132,7 @@ pub struct TableSequence<'a, V> {
     _phantom: PhantomData<V>,
 }
 
-impl<'a, V> Iterator for TableSequence<'a, V>
+impl<V> Iterator for TableSequence<'_, V>
 where
     V: FromLua,
 {

src/thread.rs

@@ -1,17 +1,17 @@
+use std::fmt;
 use std::os::raw::{c_int, c_void};
 
 use crate::error::{Error, Result};
-#[allow(unused)]
-use crate::state::Lua;
+use crate::function::Function;
 use crate::state::RawLua;
-use crate::types::ValueRef;
+use crate::traits::{FromLuaMulti, IntoLuaMulti};
+use crate::types::{LuaType, ValueRef};
 use crate::util::{check_stack, error_traceback_thread, pop_error, StackGuard};
-use crate::value::{FromLuaMulti, IntoLuaMulti};
 
 #[cfg(not(feature = "luau"))]
 use crate::{
-    hook::{Debug, HookTriggers},
-    types::MaybeSend,
+    debug::{Debug, HookTriggers},
+    types::HookKind,
 };
 
 #[cfg(feature = "async")]
@@ -41,8 +41,35 @@ pub enum ThreadStatus {
     Error,
 }
 
+/// Internal representation of a Lua thread status.
+///
+/// The number in `New` and `Yielded` variants is the number of arguments pushed
+/// to the thread stack.
+#[derive(Clone, Copy)]
+enum ThreadStatusInner {
+    New(c_int),
+    Running,
+    Yielded(c_int),
+    Finished,
+    Error,
+}
+
+impl ThreadStatusInner {
+    #[cfg(feature = "async")]
+    #[inline(always)]
+    fn is_resumable(self) -> bool {
+        matches!(self, ThreadStatusInner::New(_) | ThreadStatusInner::Yielded(_))
+    }
+
+    #[cfg(feature = "async")]
+    #[inline(always)]
+    fn is_yielded(self) -> bool {
+        matches!(self, ThreadStatusInner::Yielded(_))
+    }
+}
+
 /// Handle to an internal Lua thread (coroutine).
-#[derive(Clone, Debug)]
+#[derive(Clone)]
 pub struct Thread(pub(crate) ValueRef, pub(crate) *mut ffi::lua_State);
 
 #[cfg(feature = "send")]
@@ -52,39 +79,38 @@ unsafe impl Sync for Thread {}
 
 /// Thread (coroutine) representation as an async [`Future`] or [`Stream`].
 ///
-/// Requires `feature = "async"`
-///
 /// [`Future`]: std::future::Future
 /// [`Stream`]: futures_util::stream::Stream
 #[cfg(feature = "async")]
 #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
 #[must_use = "futures do nothing unless you `.await` or poll them"]
-pub struct AsyncThread<A, R> {
+pub struct AsyncThread<R> {
     thread: Thread,
-    init_args: Option<A>,
-    ret: PhantomData<R>,
+    ret: PhantomData<fn() -> R>,
     recycle: bool,
 }
 
 impl Thread {
+    /// Returns reference to the Lua state that this thread is associated with.
+    #[doc(hidden)]
     #[inline(always)]
-    const fn state(&self) -> *mut ffi::lua_State {
+    pub fn state(&self) -> *mut ffi::lua_State {
         self.1
     }
 
     /// Resumes execution of this thread.
     ///
-    /// Equivalent to `coroutine.resume`.
+    /// Equivalent to [`coroutine.resume`].
     ///
-    /// Passes `args` as arguments to the thread. If the coroutine has called `coroutine.yield`, it
-    /// will return these arguments. Otherwise, the coroutine wasn't yet started, so the arguments
-    /// are passed to its main function.
+    /// Passes `args` as arguments to the thread. If the coroutine has called [`coroutine.yield`],
+    /// it will return these arguments. Otherwise, the coroutine wasn't yet started, so the
+    /// arguments are passed to its main function.
     ///
-    /// If the thread is no longer in `Active` state (meaning it has finished execution or
-    /// encountered an error), this will return `Err(CoroutineInactive)`, otherwise will return `Ok`
-    /// as follows:
+    /// If the thread is no longer resumable (meaning it has finished execution or encountered an
+    /// error), this will return [`Error::CoroutineUnresumable`], otherwise will return `Ok` as
+    /// follows:
     ///
-    /// If the thread calls `coroutine.yield`, returns the values passed to `yield`. If the thread
+    /// If the thread calls [`coroutine.yield`], returns the values passed to `yield`. If the thread
     /// `return`s values from its main function, returns those.
     ///
     /// # Examples
@@ -113,14 +139,18 @@ impl Thread {
     /// # Ok(())
     /// # }
     /// ```
+    ///
+    /// [`coroutine.resume`]: https://www.lua.org/manual/5.4/manual.html#pdf-coroutine.resume
+    /// [`coroutine.yield`]: https://www.lua.org/manual/5.4/manual.html#pdf-coroutine.yield
     pub fn resume<R>(&self, args: impl IntoLuaMulti) -> Result<R>
     where
         R: FromLuaMulti,
     {
         let lua = self.0.lua.lock();
-        if self.status_inner(&lua) != ThreadStatus::Resumable {
-            return Err(Error::CoroutineUnresumable);
-        }
+        let mut pushed_nargs = match self.status_inner(&lua) {
+            ThreadStatusInner::New(nargs) | ThreadStatusInner::Yielded(nargs) => nargs,
+            _ => return Err(Error::CoroutineUnresumable),
+        };
 
         let state = lua.state();
         let thread_state = self.state();
@@ -128,7 +158,47 @@ impl Thread {
             let _sg = StackGuard::new(state);
             let _thread_sg = StackGuard::with_top(thread_state, 0);
 
-            let nresults = self.resume_inner(&lua, args)?;
+            let nargs = args.push_into_stack_multi(&lua)?;
+            if nargs > 0 {
+                check_stack(thread_state, nargs)?;
+                ffi::lua_xmove(state, thread_state, nargs);
+                pushed_nargs += nargs;
+            }
+
+            let (_, nresults) = self.resume_inner(&lua, pushed_nargs)?;
+            check_stack(state, nresults + 1)?;
+            ffi::lua_xmove(thread_state, state, nresults);
+
+            R::from_stack_multi(nresults, &lua)
+        }
+    }
+
+    /// Resumes execution of this thread, immediately raising an error.
+    ///
+    /// This is a Luau specific extension.
+    #[cfg(feature = "luau")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
+    pub fn resume_error<R>(&self, error: impl crate::IntoLua) -> Result<R>
+    where
+        R: FromLuaMulti,
+    {
+        let lua = self.0.lua.lock();
+        match self.status_inner(&lua) {
+            ThreadStatusInner::New(_) | ThreadStatusInner::Yielded(_) => {}
+            _ => return Err(Error::CoroutineUnresumable),
+        };
+
+        let state = lua.state();
+        let thread_state = self.state();
+        unsafe {
+            let _sg = StackGuard::new(state);
+            let _thread_sg = StackGuard::with_top(thread_state, 0);
+
+            check_stack(state, 1)?;
+            error.push_into_stack(&lua)?;
+            ffi::lua_xmove(state, thread_state, 1);
+
+            let (_, nresults) = self.resume_inner(&lua, ffi::LUA_RESUMEERROR)?;
             check_stack(state, nresults + 1)?;
             ffi::lua_xmove(thread_state, state, nresults);
 
@@ -139,66 +209,86 @@ impl Thread {
     /// Resumes execution of this thread.
     ///
     /// It's similar to `resume()` but leaves `nresults` values on the thread stack.
-    unsafe fn resume_inner(&self, lua: &RawLua, args: impl IntoLuaMulti) -> Result<c_int> {
+    unsafe fn resume_inner(&self, lua: &RawLua, nargs: c_int) -> Result<(ThreadStatusInner, c_int)> {
         let state = lua.state();
         let thread_state = self.state();
-
-        let nargs = args.push_into_stack_multi(&lua)?;
-        if nargs > 0 {
-            check_stack(thread_state, nargs)?;
-            ffi::lua_xmove(state, thread_state, nargs);
-        }
-
         let mut nresults = 0;
+        #[cfg(not(feature = "luau"))]
         let ret = ffi::lua_resume(thread_state, state, nargs, &mut nresults as *mut c_int);
-        if ret != ffi::LUA_OK && ret != ffi::LUA_YIELD {
-            if ret == ffi::LUA_ERRMEM {
+        #[cfg(feature = "luau")]
+        let ret = ffi::lua_resumex(thread_state, state, nargs, &mut nresults as *mut c_int);
+        match ret {
+            ffi::LUA_OK => Ok((ThreadStatusInner::Finished, nresults)),
+            ffi::LUA_YIELD => Ok((ThreadStatusInner::Yielded(0), nresults)),
+            ffi::LUA_ERRMEM => {
                 // Don't call error handler for memory errors
-                return Err(pop_error(thread_state, ret));
+                Err(pop_error(thread_state, ret))
+            }
+            _ => {
+                check_stack(state, 3)?;
+                protect_lua!(state, 0, 1, |state| error_traceback_thread(state, thread_state))?;
+                Err(pop_error(state, ret))
             }
-            check_stack(state, 3)?;
-            protect_lua!(state, 0, 1, |state| error_traceback_thread(state, thread_state))?;
-            return Err(pop_error(state, ret));
         }
-
-        Ok(nresults)
     }
 
     /// Gets the status of the thread.
     pub fn status(&self) -> ThreadStatus {
-        self.status_inner(&self.0.lua.lock())
+        match self.status_inner(&self.0.lua.lock()) {
+            ThreadStatusInner::New(_) | ThreadStatusInner::Yielded(_) => ThreadStatus::Resumable,
+            ThreadStatusInner::Running => ThreadStatus::Running,
+            ThreadStatusInner::Finished => ThreadStatus::Finished,
+            ThreadStatusInner::Error => ThreadStatus::Error,
+        }
     }
 
     /// Gets the status of the thread (internal implementation).
-    pub(crate) fn status_inner(&self, lua: &RawLua) -> ThreadStatus {
+    fn status_inner(&self, lua: &RawLua) -> ThreadStatusInner {
         let thread_state = self.state();
         if thread_state == lua.state() {
             // The thread is currently running
-            return ThreadStatus::Running;
+            return ThreadStatusInner::Running;
         }
         let status = unsafe { ffi::lua_status(thread_state) };
-        if status != ffi::LUA_OK && status != ffi::LUA_YIELD {
-            ThreadStatus::Error
-        } else if status == ffi::LUA_YIELD || unsafe { ffi::lua_gettop(thread_state) > 0 } {
-            ThreadStatus::Resumable
-        } else {
-            ThreadStatus::Finished
+        let top = unsafe { ffi::lua_gettop(thread_state) };
+        match status {
+            ffi::LUA_YIELD => ThreadStatusInner::Yielded(top),
+            ffi::LUA_OK if top > 0 => ThreadStatusInner::New(top - 1),
+            ffi::LUA_OK => ThreadStatusInner::Finished,
+            _ => ThreadStatusInner::Error,
         }
     }
 
-    /// Sets a 'hook' function that will periodically be called as Lua code executes.
+    /// Sets a hook function that will periodically be called as Lua code executes.
     ///
-    /// This function is similar or [`Lua::set_hook()`] except that it sets for the thread.
-    /// To remove a hook call [`Lua::remove_hook()`].
+    /// This function is similar or [`Lua::set_hook`] except that it sets for the thread.
+    /// You can have multiple hooks for different threads.
+    ///
+    /// To remove a hook call [`Thread::remove_hook`].
+    ///
+    /// [`Lua::set_hook`]: crate::Lua::set_hook
     #[cfg(not(feature = "luau"))]
     #[cfg_attr(docsrs, doc(cfg(not(feature = "luau"))))]
-    pub fn set_hook<F>(&self, triggers: HookTriggers, callback: F)
+    pub fn set_hook<F>(&self, triggers: HookTriggers, callback: F) -> Result<()>
     where
-        F: Fn(&Lua, Debug) -> Result<()> + MaybeSend + 'static,
+        F: Fn(&crate::Lua, &Debug) -> Result<crate::VmState> + crate::MaybeSend + 'static,
     {
         let lua = self.0.lua.lock();
         unsafe {
-            lua.set_thread_hook(self.state(), triggers, callback);
+            lua.set_thread_hook(
+                self.state(),
+                HookKind::Thread(triggers, crate::types::XRc::new(callback)),
+            )
+        }
+    }
+
+    /// Removes any hook function from this thread.
+    #[cfg(not(feature = "luau"))]
+    #[cfg_attr(docsrs, doc(cfg(not(feature = "luau"))))]
+    pub fn remove_hook(&self) {
+        let _lua = self.0.lua.lock();
+        unsafe {
+            ffi::lua_sethook(self.state(), None, 0, 0);
         }
     }
 
@@ -211,31 +301,17 @@ impl Thread {
     /// In Luau: resets to the initial state of a newly created Lua thread.
     /// Lua threads in arbitrary states (like yielded or errored) can be reset properly.
     ///
+    /// Other Lua versions can reset only new or finished threads.
+    ///
     /// Sets a Lua function for the thread afterwards.
     ///
-    /// Requires `feature = "lua54"` OR `feature = "luau"`.
-    ///
     /// [Lua 5.4]: https://www.lua.org/manual/5.4/manual.html#lua_closethread
-    #[cfg(any(feature = "lua54", feature = "luau"))]
-    #[cfg_attr(docsrs, doc(cfg(any(feature = "lua54", feature = "luau"))))]
-    pub fn reset(&self, func: crate::function::Function) -> Result<()> {
+    pub fn reset(&self, func: Function) -> Result<()> {
         let lua = self.0.lua.lock();
-        if self.status_inner(&lua) == ThreadStatus::Running {
-            return Err(Error::runtime("cannot reset a running thread"));
-        }
-
         let thread_state = self.state();
         unsafe {
-            #[cfg(all(feature = "lua54", not(feature = "vendored")))]
-            let status = ffi::lua_resetthread(thread_state);
-            #[cfg(all(feature = "lua54", feature = "vendored"))]
-            let status = ffi::lua_closethread(thread_state, lua.state());
-            #[cfg(feature = "lua54")]
-            if status != ffi::LUA_OK {
-                return Err(pop_error(thread_state, status));
-            }
-            #[cfg(feature = "luau")]
-            ffi::lua_resetthread(thread_state);
+            let status = self.status_inner(&lua);
+            self.reset_inner(status)?;
 
             // Push function to the top of the thread stack
             ffi::lua_xpush(lua.ref_thread(), thread_state, func.0.index);
@@ -251,21 +327,58 @@ impl Thread {
         }
     }
 
-    /// Converts Thread to an AsyncThread which implements [`Future`] and [`Stream`] traits.
+    unsafe fn reset_inner(&self, status: ThreadStatusInner) -> Result<()> {
+        match status {
+            ThreadStatusInner::New(_) => {
+                // The thread is new, so we can just set the top to 0
+                ffi::lua_settop(self.state(), 0);
+                Ok(())
+            }
+            ThreadStatusInner::Running => Err(Error::runtime("cannot reset a running thread")),
+            ThreadStatusInner::Finished => Ok(()),
+            #[cfg(not(any(feature = "lua54", feature = "luau")))]
+            ThreadStatusInner::Yielded(_) | ThreadStatusInner::Error => {
+                Err(Error::runtime("cannot reset non-finished thread"))
+            }
+            #[cfg(any(feature = "lua54", feature = "luau"))]
+            ThreadStatusInner::Yielded(_) | ThreadStatusInner::Error => {
+                let thread_state = self.state();
+
+                #[cfg(all(feature = "lua54", not(feature = "vendored")))]
+                let status = ffi::lua_resetthread(thread_state);
+                #[cfg(all(feature = "lua54", feature = "vendored"))]
+                let status = {
+                    let lua = self.0.lua.lock();
+                    ffi::lua_closethread(thread_state, lua.state())
+                };
+                #[cfg(feature = "lua54")]
+                if status != ffi::LUA_OK {
+                    return Err(pop_error(thread_state, status));
+                }
+                #[cfg(feature = "luau")]
+                ffi::lua_resetthread(thread_state);
+
+                Ok(())
+            }
+        }
+    }
+
+    /// Converts [`Thread`] to an [`AsyncThread`] which implements [`Future`] and [`Stream`] traits.
     ///
-    /// `args` are passed as arguments to the thread function for first call.
-    /// The object calls [`resume()`] while polling and also allows to run rust futures
+    /// Only resumable threads can be converted to [`AsyncThread`].
+    ///
+    /// `args` are pushed to the thread stack and will be used when the thread is resumed.
+    /// The object calls [`resume`] while polling and also allow to run Rust futures
     /// to completion using an executor.
     ///
-    /// Using AsyncThread as a Stream allows to iterate through `coroutine.yield()`
-    /// values whereas Future version discards that values and poll until the final
+    /// Using [`AsyncThread`] as a [`Stream`] allow to iterate through [`coroutine.yield`]
+    /// values whereas [`Future`] version discards that values and poll until the final
     /// one (returned from the thread function).
     ///
-    /// Requires `feature = "async"`
-    ///
     /// [`Future`]: std::future::Future
     /// [`Stream`]: futures_util::stream::Stream
-    /// [`resume()`]: https://www.lua.org/manual/5.4/manual.html#lua_resume
+    /// [`resume`]: https://www.lua.org/manual/5.4/manual.html#lua_resume
+    /// [`coroutine.yield`]: https://www.lua.org/manual/5.4/manual.html#pdf-coroutine.yield
     ///
     /// # Examples
     ///
@@ -285,7 +398,7 @@ impl Thread {
     ///     end)
     /// "#).eval()?;
     ///
-    /// let mut stream = thread.into_async::<i64>(1);
+    /// let mut stream = thread.into_async::<i64>(1)?;
     /// let mut sum = 0;
     /// while let Some(n) = stream.try_next().await? {
     ///     sum += n;
@@ -298,15 +411,31 @@ impl Thread {
     /// ```
     #[cfg(feature = "async")]
     #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
-    pub fn into_async<R>(self, args: impl IntoLuaMulti) -> AsyncThread<impl IntoLuaMulti, R>
+    pub fn into_async<R>(self, args: impl IntoLuaMulti) -> Result<AsyncThread<R>>
     where
         R: FromLuaMulti,
     {
-        AsyncThread {
-            thread: self,
-            init_args: Some(args),
-            ret: PhantomData,
-            recycle: false,
+        let lua = self.0.lua.lock();
+        if !self.status_inner(&lua).is_resumable() {
+            return Err(Error::CoroutineUnresumable);
+        }
+
+        let state = lua.state();
+        let thread_state = self.state();
+        unsafe {
+            let _sg = StackGuard::new(state);
+
+            let nargs = args.push_into_stack_multi(&lua)?;
+            if nargs > 0 {
+                check_stack(thread_state, nargs)?;
+                ffi::lua_xmove(state, thread_state, nargs);
+            }
+
+            Ok(AsyncThread {
+                thread: self,
+                ret: PhantomData,
+                recycle: false,
+            })
         }
     }
 
@@ -315,7 +444,7 @@ impl Thread {
     /// Under the hood replaces the global environment table with a new table,
     /// that performs writes locally and proxies reads to caller's global environment.
     ///
-    /// This mode ideally should be used together with the global sandbox mode [`Lua::sandbox()`].
+    /// This mode ideally should be used together with the global sandbox mode [`Lua::sandbox`].
     ///
     /// Please note that Luau links environment table with chunk when loading it into Lua state.
     /// Therefore you need to load chunks into a thread to link with the thread environment.
@@ -324,6 +453,7 @@ impl Thread {
     ///
     /// ```
     /// # use mlua::{Lua, Result};
+    /// # #[cfg(feature = "luau")]
     /// # fn main() -> Result<()> {
     /// let lua = Lua::new();
     /// let thread = lua.create_thread(lua.create_function(|lua2, ()| {
@@ -332,18 +462,18 @@ impl Thread {
     ///     Ok(())
     /// })?)?;
     /// thread.sandbox()?;
-    /// thread.resume(())?;
+    /// thread.resume::<()>(())?;
     ///
     /// // The global environment should be unchanged
     /// assert_eq!(lua.globals().get::<Option<u32>>("var")?, None);
     /// # Ok(())
     /// # }
-    /// ```
     ///
-    /// Requires `feature = "luau"`
-    #[cfg(any(feature = "luau", docsrs))]
+    /// # #[cfg(not(feature = "luau"))]
+    /// # fn main() { }
+    /// ```
+    #[cfg(any(feature = "luau", doc))]
     #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
-    #[doc(hidden)]
     pub fn sandbox(&self) -> Result<()> {
         let lua = self.0.lua.lock();
         let state = lua.state();
@@ -366,37 +496,50 @@ impl Thread {
     }
 }
 
+impl fmt::Debug for Thread {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt.debug_tuple("Thread").field(&self.0).finish()
+    }
+}
+
 impl PartialEq for Thread {
     fn eq(&self, other: &Self) -> bool {
         self.0 == other.0
     }
 }
 
+impl LuaType for Thread {
+    const TYPE_ID: c_int = ffi::LUA_TTHREAD;
+}
+
 #[cfg(feature = "async")]
-impl<A, R> AsyncThread<A, R> {
-    #[inline]
+impl<R> AsyncThread<R> {
+    #[inline(always)]
     pub(crate) fn set_recyclable(&mut self, recyclable: bool) {
         self.recycle = recyclable;
     }
 }
 
 #[cfg(feature = "async")]
-#[cfg(any(feature = "lua54", feature = "luau"))]
-impl<A, R> Drop for AsyncThread<A, R> {
+impl<R> Drop for AsyncThread<R> {
     fn drop(&mut self) {
         if self.recycle {
             if let Some(lua) = self.thread.0.lua.try_lock() {
                 unsafe {
-                    // For Lua 5.4 this also closes all pending to-be-closed variables
-                    if !lua.recycle_thread(&mut self.thread) {
-                        #[cfg(feature = "lua54")]
-                        if self.thread.status_inner(&lua) == ThreadStatus::Error {
-                            #[cfg(not(feature = "vendored"))]
-                            ffi::lua_resetthread(self.thread.state());
-                            #[cfg(feature = "vendored")]
-                            ffi::lua_closethread(self.thread.state(), lua.state());
+                    let mut status = self.thread.status_inner(&lua);
+                    if matches!(status, ThreadStatusInner::Yielded(0)) {
+                        // The thread is dropped while yielded, resume it with the "terminate" signal
+                        ffi::lua_pushlightuserdata(self.thread.1, crate::Lua::poll_terminate().0);
+                        if let Ok((new_status, _)) = self.thread.resume_inner(&lua, 1) {
+                            // `new_status` should always be `ThreadStatusInner::Yielded(0)`
+                            status = new_status;
                         }
                     }
+
+                    // For Lua 5.4 this also closes all pending to-be-closed variables
+                    if self.thread.reset_inner(status).is_ok() {
+                        lua.recycle_thread(&mut self.thread);
+                    }
                 }
             }
         }
@@ -404,14 +547,15 @@ impl<A, R> Drop for AsyncThread<A, R> {
 }
 
 #[cfg(feature = "async")]
-impl<A: IntoLuaMulti, R: FromLuaMulti> Stream for AsyncThread<A, R> {
+impl<R: FromLuaMulti> Stream for AsyncThread<R> {
     type Item = Result<R>;
 
     fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
         let lua = self.thread.0.lua.lock();
-        if self.thread.status_inner(&lua) != ThreadStatus::Resumable {
-            return Poll::Ready(None);
-        }
+        let nargs = match self.thread.status_inner(&lua) {
+            ThreadStatusInner::New(nargs) | ThreadStatusInner::Yielded(nargs) => nargs,
+            _ => return Poll::Ready(None),
+        };
 
         let state = lua.state();
         let thread_state = self.thread.state();
@@ -420,36 +564,34 @@ impl<A: IntoLuaMulti, R: FromLuaMulti> Stream for AsyncThread<A, R> {
             let _thread_sg = StackGuard::with_top(thread_state, 0);
             let _wg = WakerGuard::new(&lua, cx.waker());
 
-            // This is safe as we are not moving the whole struct
-            let this = self.get_unchecked_mut();
-            let nresults = if let Some(args) = this.init_args.take() {
-                this.thread.resume_inner(&lua, args)?
-            } else {
-                this.thread.resume_inner(&lua, ())?
-            };
+            let (status, nresults) = (self.thread).resume_inner(&lua, nargs)?;
 
-            if nresults == 1 && is_poll_pending(thread_state) {
-                return Poll::Pending;
+            if status.is_yielded() {
+                if nresults == 1 && is_poll_pending(thread_state) {
+                    return Poll::Pending;
+                }
+                // Continue polling
+                cx.waker().wake_by_ref();
             }
 
             check_stack(state, nresults + 1)?;
             ffi::lua_xmove(thread_state, state, nresults);
 
-            cx.waker().wake_by_ref();
             Poll::Ready(Some(R::from_stack_multi(nresults, &lua)))
         }
     }
 }
 
 #[cfg(feature = "async")]
-impl<A: IntoLuaMulti, R: FromLuaMulti> Future for AsyncThread<A, R> {
+impl<R: FromLuaMulti> Future for AsyncThread<R> {
     type Output = Result<R>;
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
         let lua = self.thread.0.lua.lock();
-        if self.thread.status_inner(&lua) != ThreadStatus::Resumable {
-            return Poll::Ready(Err(Error::CoroutineUnresumable));
-        }
+        let nargs = match self.thread.status_inner(&lua) {
+            ThreadStatusInner::New(nargs) | ThreadStatusInner::Yielded(nargs) => nargs,
+            _ => return Poll::Ready(Err(Error::CoroutineUnresumable)),
+        };
 
         let state = lua.state();
         let thread_state = self.thread.state();
@@ -458,21 +600,13 @@ impl<A: IntoLuaMulti, R: FromLuaMulti> Future for AsyncThread<A, R> {
             let _thread_sg = StackGuard::with_top(thread_state, 0);
             let _wg = WakerGuard::new(&lua, cx.waker());
 
-            // This is safe as we are not moving the whole struct
-            let this = self.get_unchecked_mut();
-            let nresults = if let Some(args) = this.init_args.take() {
-                this.thread.resume_inner(&lua, args)?
-            } else {
-                this.thread.resume_inner(&lua, ())?
-            };
+            let (status, nresults) = self.thread.resume_inner(&lua, nargs)?;
 
-            if nresults == 1 && is_poll_pending(thread_state) {
-                return Poll::Pending;
-            }
-
-            if ffi::lua_status(thread_state) == ffi::LUA_YIELD {
-                // Ignore value returned via yield()
-                cx.waker().wake_by_ref();
+            if status.is_yielded() {
+                if !(nresults == 1 && is_poll_pending(thread_state)) {
+                    // Ignore value returned via yield()
+                    cx.waker().wake_by_ref();
+                }
                 return Poll::Pending;
             }
 
@@ -487,7 +621,7 @@ impl<A: IntoLuaMulti, R: FromLuaMulti> Future for AsyncThread<A, R> {
 #[cfg(feature = "async")]
 #[inline(always)]
 unsafe fn is_poll_pending(state: *mut ffi::lua_State) -> bool {
-    ffi::lua_tolightuserdata(state, -1) == Lua::poll_pending().0
+    ffi::lua_tolightuserdata(state, -1) == crate::Lua::poll_pending().0
 }
 
 #[cfg(feature = "async")]
@@ -511,7 +645,7 @@ impl<'lua, 'a> WakerGuard<'lua, 'a> {
 }
 
 #[cfg(feature = "async")]
-impl<'lua, 'a> Drop for WakerGuard<'lua, 'a> {
+impl Drop for WakerGuard<'_, '_> {
     fn drop(&mut self) {
         unsafe { self.lua.set_waker(self.prev) };
     }
@@ -526,7 +660,7 @@ mod assertions {
     #[cfg(feature = "send")]
     static_assertions::assert_impl_all!(Thread: Send, Sync);
     #[cfg(all(feature = "async", not(feature = "send")))]
-    static_assertions::assert_not_impl_any!(AsyncThread<(), ()>: Send);
+    static_assertions::assert_not_impl_any!(AsyncThread<()>: Send);
     #[cfg(all(feature = "async", feature = "send"))]
-    static_assertions::assert_impl_all!(AsyncThread<(), ()>: Send, Sync);
+    static_assertions::assert_impl_all!(AsyncThread<()>: Send, Sync);
 }

src/traits.rs

@@ -1,11 +1,144 @@
+use std::os::raw::c_int;
 use std::string::String as StdString;
+use std::sync::Arc;
 
-use crate::error::Result;
+use crate::error::{Error, Result};
+use crate::multi::MultiValue;
 use crate::private::Sealed;
-use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti};
+use crate::state::{Lua, RawLua};
+use crate::types::MaybeSend;
+use crate::util::{check_stack, short_type_name};
+use crate::value::Value;
 
 #[cfg(feature = "async")]
-use std::future::Future;
+use {crate::function::AsyncCallFuture, std::future::Future};
+
+/// Trait for types convertible to [`Value`].
+pub trait IntoLua: Sized {
+    /// Performs the conversion.
+    fn into_lua(self, lua: &Lua) -> Result<Value>;
+
+    /// Pushes the value into the Lua stack.
+    ///
+    /// # Safety
+    /// This method does not check Lua stack space.
+    #[doc(hidden)]
+    #[inline]
+    unsafe fn push_into_stack(self, lua: &RawLua) -> Result<()> {
+        lua.push_value(&self.into_lua(lua.lua())?)
+    }
+}
+
+/// Trait for types convertible from [`Value`].
+pub trait FromLua: Sized {
+    /// Performs the conversion.
+    fn from_lua(value: Value, lua: &Lua) -> Result<Self>;
+
+    /// Performs the conversion for an argument (eg. function argument).
+    ///
+    /// `i` is the argument index (position),
+    /// `to` is a function name that received the argument.
+    #[doc(hidden)]
+    #[inline]
+    fn from_lua_arg(arg: Value, i: usize, to: Option<&str>, lua: &Lua) -> Result<Self> {
+        Self::from_lua(arg, lua).map_err(|err| Error::BadArgument {
+            to: to.map(|s| s.to_string()),
+            pos: i,
+            name: None,
+            cause: Arc::new(err),
+        })
+    }
+
+    /// Performs the conversion for a value in the Lua stack at index `idx`.
+    #[doc(hidden)]
+    #[inline]
+    unsafe fn from_stack(idx: c_int, lua: &RawLua) -> Result<Self> {
+        Self::from_lua(lua.stack_value(idx, None), lua.lua())
+    }
+
+    /// Same as `from_lua_arg` but for a value in the Lua stack at index `idx`.
+    #[doc(hidden)]
+    #[inline]
+    unsafe fn from_stack_arg(idx: c_int, i: usize, to: Option<&str>, lua: &RawLua) -> Result<Self> {
+        Self::from_stack(idx, lua).map_err(|err| Error::BadArgument {
+            to: to.map(|s| s.to_string()),
+            pos: i,
+            name: None,
+            cause: Arc::new(err),
+        })
+    }
+}
+
+/// Trait for types convertible to any number of Lua values.
+///
+/// This is a generalization of [`IntoLua`], allowing any number of resulting Lua values instead of
+/// just one. Any type that implements [`IntoLua`] will automatically implement this trait.
+pub trait IntoLuaMulti: Sized {
+    /// Performs the conversion.
+    fn into_lua_multi(self, lua: &Lua) -> Result<MultiValue>;
+
+    /// Pushes the values into the Lua stack.
+    ///
+    /// Returns number of pushed values.
+    #[doc(hidden)]
+    #[inline]
+    unsafe fn push_into_stack_multi(self, lua: &RawLua) -> Result<c_int> {
+        let values = self.into_lua_multi(lua.lua())?;
+        let len: c_int = values.len().try_into().unwrap();
+        unsafe {
+            check_stack(lua.state(), len + 1)?;
+            for val in &values {
+                lua.push_value(val)?;
+            }
+        }
+        Ok(len)
+    }
+}
+
+/// Trait for types that can be created from an arbitrary number of Lua values.
+///
+/// This is a generalization of [`FromLua`], allowing an arbitrary number of Lua values to
+/// participate in the conversion. Any type that implements [`FromLua`] will automatically
+/// implement this trait.
+pub trait FromLuaMulti: Sized {
+    /// Performs the conversion.
+    ///
+    /// In case `values` contains more values than needed to perform the conversion, the excess
+    /// values should be ignored. This reflects the semantics of Lua when calling a function or
+    /// assigning values. Similarly, if not enough values are given, conversions should assume that
+    /// any missing values are nil.
+    fn from_lua_multi(values: MultiValue, lua: &Lua) -> Result<Self>;
+
+    /// Performs the conversion for a list of arguments.
+    ///
+    /// `i` is an index (position) of the first argument,
+    /// `to` is a function name that received the arguments.
+    #[doc(hidden)]
+    #[inline]
+    fn from_lua_args(args: MultiValue, i: usize, to: Option<&str>, lua: &Lua) -> Result<Self> {
+        let _ = (i, to);
+        Self::from_lua_multi(args, lua)
+    }
+
+    /// Performs the conversion for a number of values in the Lua stack.
+    #[doc(hidden)]
+    #[inline]
+    unsafe fn from_stack_multi(nvals: c_int, lua: &RawLua) -> Result<Self> {
+        let mut values = MultiValue::with_capacity(nvals as usize);
+        for idx in 0..nvals {
+            values.push_back(lua.stack_value(-nvals + idx, None));
+        }
+        Self::from_lua_multi(values, lua.lua())
+    }
+
+    /// Same as `from_lua_args` but for a number of values in the Lua stack.
+    #[doc(hidden)]
+    #[inline]
+    unsafe fn from_stack_args(nargs: c_int, i: usize, to: Option<&str>, lua: &RawLua) -> Result<Self> {
+        let _ = (i, to);
+        Self::from_stack_multi(nargs, lua)
+    }
+}
 
 /// A trait for types that can be used as Lua objects (usually table and userdata).
 pub trait ObjectLike: Sealed {
@@ -29,7 +162,7 @@ pub trait ObjectLike: Sealed {
     /// arguments.
     #[cfg(feature = "async")]
     #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
-    fn call_async<R>(&self, args: impl IntoLuaMulti) -> impl Future<Output = Result<R>>
+    fn call_async<R>(&self, args: impl IntoLuaMulti) -> AsyncCallFuture<R>
     where
         R: FromLuaMulti;
 
@@ -42,12 +175,10 @@ pub trait ObjectLike: Sealed {
     /// Gets the function associated to key `name` from the object and asynchronously calls it,
     /// passing the object itself along with `args` as function arguments.
     ///
-    /// Requires `feature = "async"`
-    ///
     /// This might invoke the `__index` metamethod.
     #[cfg(feature = "async")]
     #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
-    fn call_async_method<R>(&self, name: &str, args: impl IntoLuaMulti) -> impl Future<Output = Result<R>>
+    fn call_async_method<R>(&self, name: &str, args: impl IntoLuaMulti) -> AsyncCallFuture<R>
     where
         R: FromLuaMulti;
 
@@ -62,12 +193,10 @@ pub trait ObjectLike: Sealed {
     /// Gets the function associated to key `name` from the object and asynchronously calls it,
     /// passing `args` as function arguments.
     ///
-    /// Requires `feature = "async"`
-    ///
     /// This might invoke the `__index` metamethod.
     #[cfg(feature = "async")]
     #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
-    fn call_async_function<R>(&self, name: &str, args: impl IntoLuaMulti) -> impl Future<Output = Result<R>>
+    fn call_async_function<R>(&self, name: &str, args: impl IntoLuaMulti) -> AsyncCallFuture<R>
     where
         R: FromLuaMulti;
 
@@ -76,3 +205,103 @@ pub trait ObjectLike: Sealed {
     /// This might invoke the `__tostring` metamethod.
     fn to_string(&self) -> Result<StdString>;
 }
+
+/// A trait for types that can be used as Lua functions.
+pub trait LuaNativeFn<A: FromLuaMulti> {
+    type Output: IntoLuaMulti;
+
+    fn call(&self, args: A) -> Self::Output;
+}
+
+/// A trait for types with mutable state that can be used as Lua functions.
+pub trait LuaNativeFnMut<A: FromLuaMulti> {
+    type Output: IntoLuaMulti;
+
+    fn call(&mut self, args: A) -> Self::Output;
+}
+
+/// A trait for types that returns a future and can be used as Lua functions.
+#[cfg(feature = "async")]
+pub trait LuaNativeAsyncFn<A: FromLuaMulti> {
+    type Output: IntoLuaMulti;
+
+    fn call(&self, args: A) -> impl Future<Output = Self::Output> + MaybeSend + 'static;
+}
+
+macro_rules! impl_lua_native_fn {
+    ($($A:ident),*) => {
+        impl<FN, $($A,)* R> LuaNativeFn<($($A,)*)> for FN
+        where
+            FN: Fn($($A,)*) -> R + MaybeSend + 'static,
+            ($($A,)*): FromLuaMulti,
+            R: IntoLuaMulti,
+        {
+            type Output = R;
+
+            #[allow(non_snake_case)]
+            fn call(&self, args: ($($A,)*)) -> Self::Output {
+                let ($($A,)*) = args;
+                self($($A,)*)
+            }
+        }
+
+        impl<FN, $($A,)* R> LuaNativeFnMut<($($A,)*)> for FN
+        where
+            FN: FnMut($($A,)*) -> R + MaybeSend + 'static,
+            ($($A,)*): FromLuaMulti,
+            R: IntoLuaMulti,
+        {
+            type Output = R;
+
+            #[allow(non_snake_case)]
+            fn call(&mut self, args: ($($A,)*)) -> Self::Output {
+                let ($($A,)*) = args;
+                self($($A,)*)
+            }
+        }
+
+        #[cfg(feature = "async")]
+        impl<FN, $($A,)* Fut, R> LuaNativeAsyncFn<($($A,)*)> for FN
+        where
+            FN: Fn($($A,)*) -> Fut + MaybeSend + 'static,
+            ($($A,)*): FromLuaMulti,
+            Fut: Future<Output = R> + MaybeSend + 'static,
+            R: IntoLuaMulti,
+        {
+            type Output = R;
+
+            #[allow(non_snake_case)]
+            fn call(&self, args: ($($A,)*)) -> impl Future<Output = Self::Output> + MaybeSend + 'static {
+                let ($($A,)*) = args;
+                self($($A,)*)
+            }
+        }
+    };
+}
+
+impl_lua_native_fn!();
+impl_lua_native_fn!(A);
+impl_lua_native_fn!(A, B);
+impl_lua_native_fn!(A, B, C);
+impl_lua_native_fn!(A, B, C, D);
+impl_lua_native_fn!(A, B, C, D, E);
+impl_lua_native_fn!(A, B, C, D, E, F);
+impl_lua_native_fn!(A, B, C, D, E, F, G);
+impl_lua_native_fn!(A, B, C, D, E, F, G, H);
+impl_lua_native_fn!(A, B, C, D, E, F, G, H, I);
+impl_lua_native_fn!(A, B, C, D, E, F, G, H, I, J);
+impl_lua_native_fn!(A, B, C, D, E, F, G, H, I, J, K);
+impl_lua_native_fn!(A, B, C, D, E, F, G, H, I, J, K, L);
+impl_lua_native_fn!(A, B, C, D, E, F, G, H, I, J, K, L, M);
+impl_lua_native_fn!(A, B, C, D, E, F, G, H, I, J, K, L, M, N);
+impl_lua_native_fn!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O);
+impl_lua_native_fn!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P);
+
+pub(crate) trait ShortTypeName {
+    #[inline(always)]
+    fn type_name() -> StdString {
+        short_type_name::<Self>()
+    }
+}
+
+impl<T> ShortTypeName for T {}

src/types.rs

@@ -1,12 +1,10 @@
 use std::cell::UnsafeCell;
-use std::fmt;
 use std::os::raw::{c_int, c_void};
-use std::rc::Rc;
 
-use crate::error::Result;
 #[cfg(not(feature = "luau"))]
-use crate::hook::Debug;
-use crate::state::{ExtraData, Lua, RawLua, WeakLua};
+use crate::debug::{Debug, HookTriggers};
+use crate::error::Result;
+use crate::state::{ExtraData, Lua, RawLua};
 
 // Re-export mutex wrappers
 pub(crate) use sync::{ArcReentrantMutexGuard, ReentrantMutex, ReentrantMutexGuard, XRc, XWeak};
@@ -18,25 +16,15 @@ pub(crate) type BoxFuture<'a, T> = futures_util::future::BoxFuture<'a, T>;
 pub(crate) type BoxFuture<'a, T> = futures_util::future::LocalBoxFuture<'a, T>;
 
 pub use app_data::{AppData, AppDataRef, AppDataRefMut};
+pub use either::Either;
 pub use registry_key::RegistryKey;
-#[cfg(any(feature = "luau", doc))]
-pub use vector::Vector;
+pub(crate) use value_ref::ValueRef;
 
 /// Type of Lua integer numbers.
 pub type Integer = ffi::lua_Integer;
 /// Type of Lua floating point numbers.
 pub type Number = ffi::lua_Number;
 
-// Represents different subtypes wrapped to AnyUserData
-#[derive(Debug, Copy, Clone, Eq, PartialEq)]
-pub(crate) enum SubtypeId {
-    None,
-    #[cfg(feature = "luau")]
-    Buffer,
-    #[cfg(feature = "luajit")]
-    CData,
-}
-
 /// A "light" userdata value. Equivalent to an unmanaged raw pointer.
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 pub struct LightUserData(pub *mut c_void);
@@ -52,12 +40,14 @@ pub(crate) type Callback = Box<dyn Fn(&RawLua, c_int) -> Result<c_int> + Send +
 #[cfg(not(feature = "send"))]
 pub(crate) type Callback = Box<dyn Fn(&RawLua, c_int) -> Result<c_int> + 'static>;
 
+pub(crate) type ScopedCallback<'s> = Box<dyn Fn(&RawLua, c_int) -> Result<c_int> + 's>;
+
 pub(crate) struct Upvalue<T> {
     pub(crate) data: T,
     pub(crate) extra: XRc<UnsafeCell<ExtraData>>,
 }
 
-pub(crate) type CallbackUpvalue = Upvalue<Callback>;
+pub(crate) type CallbackUpvalue = Upvalue<Option<Callback>>;
 
 #[cfg(all(feature = "async", feature = "send"))]
 pub(crate) type AsyncCallback =
@@ -71,33 +61,52 @@ pub(crate) type AsyncCallback =
 pub(crate) type AsyncCallbackUpvalue = Upvalue<AsyncCallback>;
 
 #[cfg(feature = "async")]
-pub(crate) type AsyncPollUpvalue = Upvalue<BoxFuture<'static, Result<c_int>>>;
+pub(crate) type AsyncPollUpvalue = Upvalue<Option<BoxFuture<'static, Result<c_int>>>>;
 
-/// Type to set next Luau VM action after executing interrupt function.
-#[cfg(any(feature = "luau", doc))]
-#[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
+/// Type to set next Lua VM action after executing interrupt or hook function.
 pub enum VmState {
     Continue,
+    /// Yield the current thread.
+    ///
+    /// Supported by Lua 5.3+ and Luau.
     Yield,
 }
 
+#[cfg(not(feature = "luau"))]
+pub(crate) enum HookKind {
+    Global,
+    Thread(HookTriggers, HookCallback),
+}
+
 #[cfg(all(feature = "send", not(feature = "luau")))]
-pub(crate) type HookCallback = Rc<dyn Fn(&Lua, Debug) -> Result<()> + Send>;
+pub(crate) type HookCallback = XRc<dyn Fn(&Lua, &Debug) -> Result<VmState> + Send>;
 
 #[cfg(all(not(feature = "send"), not(feature = "luau")))]
-pub(crate) type HookCallback = Rc<dyn Fn(&Lua, Debug) -> Result<()>>;
+pub(crate) type HookCallback = XRc<dyn Fn(&Lua, &Debug) -> Result<VmState>>;
 
 #[cfg(all(feature = "send", feature = "luau"))]
-pub(crate) type InterruptCallback = Rc<dyn Fn(&Lua) -> Result<VmState> + Send>;
+pub(crate) type InterruptCallback = XRc<dyn Fn(&Lua) -> Result<VmState> + Send>;
 
 #[cfg(all(not(feature = "send"), feature = "luau"))]
-pub(crate) type InterruptCallback = Rc<dyn Fn(&Lua) -> Result<VmState>>;
+pub(crate) type InterruptCallback = XRc<dyn Fn(&Lua) -> Result<VmState>>;
+
+#[cfg(all(feature = "send", feature = "luau"))]
+pub(crate) type ThreadCreationCallback = XRc<dyn Fn(&Lua, crate::Thread) -> Result<()> + Send>;
+
+#[cfg(all(not(feature = "send"), feature = "luau"))]
+pub(crate) type ThreadCreationCallback = XRc<dyn Fn(&Lua, crate::Thread) -> Result<()>>;
+
+#[cfg(all(feature = "send", feature = "luau"))]
+pub(crate) type ThreadCollectionCallback = XRc<dyn Fn(crate::LightUserData) + Send>;
+
+#[cfg(all(not(feature = "send"), feature = "luau"))]
+pub(crate) type ThreadCollectionCallback = XRc<dyn Fn(crate::LightUserData)>;
 
 #[cfg(all(feature = "send", feature = "lua54"))]
-pub(crate) type WarnCallback = Box<dyn Fn(&Lua, &str, bool) -> Result<()> + Send>;
+pub(crate) type WarnCallback = XRc<dyn Fn(&Lua, &str, bool) -> Result<()> + Send>;
 
 #[cfg(all(not(feature = "send"), feature = "lua54"))]
-pub(crate) type WarnCallback = Box<dyn Fn(&Lua, &str, bool) -> Result<()>>;
+pub(crate) type WarnCallback = XRc<dyn Fn(&Lua, &str, bool) -> Result<()>>;
 
 /// A trait that adds `Send` requirement if `send` feature is enabled.
 #[cfg(feature = "send")]
@@ -112,78 +121,26 @@ impl<T> MaybeSend for T {}
 
 pub(crate) struct DestructedUserdata;
 
-pub(crate) struct ValueRef {
-    pub(crate) lua: WeakLua,
-    pub(crate) index: c_int,
-    pub(crate) drop: bool,
+pub(crate) trait LuaType {
+    const TYPE_ID: c_int;
 }
 
-impl ValueRef {
-    #[inline]
-    pub(crate) fn new(lua: &RawLua, index: c_int) -> Self {
-        ValueRef {
-            lua: lua.weak().clone(),
-            index,
-            drop: true,
-        }
-    }
-
-    #[inline]
-    pub(crate) fn to_pointer(&self) -> *const c_void {
-        let lua = self.lua.lock();
-        unsafe { ffi::lua_topointer(lua.ref_thread(), self.index) }
-    }
-
-    /// Returns a copy of the value, which is valid as long as the original value is held.
-    #[inline]
-    pub(crate) fn copy(&self) -> Self {
-        ValueRef {
-            lua: self.lua.clone(),
-            index: self.index,
-            drop: false,
-        }
-    }
+impl LuaType for bool {
+    const TYPE_ID: c_int = ffi::LUA_TBOOLEAN;
 }
 
-impl fmt::Debug for ValueRef {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "Ref({:p})", self.to_pointer())
-    }
+impl LuaType for Number {
+    const TYPE_ID: c_int = ffi::LUA_TNUMBER;
 }
 
-impl Clone for ValueRef {
-    fn clone(&self) -> Self {
-        unsafe { self.lua.lock().clone_ref(self) }
-    }
-}
-
-impl Drop for ValueRef {
-    fn drop(&mut self) {
-        if self.drop {
-            if let Some(lua) = self.lua.try_lock() {
-                unsafe { lua.drop_ref(self) };
-            }
-        }
-    }
-}
-
-impl PartialEq for ValueRef {
-    fn eq(&self, other: &Self) -> bool {
-        assert!(
-            self.lua == other.lua,
-            "Lua instance passed Value created from a different main Lua state"
-        );
-        let lua = self.lua.lock();
-        unsafe { ffi::lua_rawequal(lua.ref_thread(), self.index, other.index) == 1 }
-    }
+impl LuaType for LightUserData {
+    const TYPE_ID: c_int = ffi::LUA_TLIGHTUSERDATA;
 }
 
 mod app_data;
 mod registry_key;
 mod sync;
-
-#[cfg(any(feature = "luau", doc))]
-mod vector;
+mod value_ref;
 
 #[cfg(test)]
 mod assertions {

src/types/app_data.rs

@@ -1,5 +1,5 @@
 use std::any::{Any, TypeId};
-use std::cell::{Cell, Ref, RefCell, RefMut, UnsafeCell};
+use std::cell::{BorrowError, BorrowMutError, Cell, Ref, RefCell, RefMut, UnsafeCell};
 use std::fmt;
 use std::ops::{Deref, DerefMut};
 use std::result::Result as StdResult;
@@ -41,30 +41,66 @@ impl AppData {
             .and_then(|data| data.into_inner().downcast::<T>().ok().map(|data| *data)))
     }
 
+    #[inline]
     #[track_caller]
-    pub(crate) fn borrow<T: 'static>(&self, guard: Option<LuaGuard>) -> Option<AppDataRef<T>> {
-        let data = unsafe { &*self.container.get() }
-            .get(&TypeId::of::<T>())?
-            .borrow();
-        self.borrow.set(self.borrow.get() + 1);
-        Some(AppDataRef {
-            data: Ref::filter_map(data, |data| data.downcast_ref()).ok()?,
-            borrow: &self.borrow,
-            _guard: guard,
-        })
+    pub(crate) fn borrow<T: 'static>(&self, guard: Option<LuaGuard>) -> Option<AppDataRef<'_, T>> {
+        match self.try_borrow(guard) {
+            Ok(data) => data,
+            Err(err) => panic!("already mutably borrowed: {err:?}"),
+        }
     }
 
-    #[track_caller]
-    pub(crate) fn borrow_mut<T: 'static>(&self, guard: Option<LuaGuard>) -> Option<AppDataRefMut<T>> {
+    pub(crate) fn try_borrow<T: 'static>(
+        &self,
+        guard: Option<LuaGuard>,
+    ) -> Result<Option<AppDataRef<'_, T>>, BorrowError> {
         let data = unsafe { &*self.container.get() }
-            .get(&TypeId::of::<T>())?
-            .borrow_mut();
-        self.borrow.set(self.borrow.get() + 1);
-        Some(AppDataRefMut {
-            data: RefMut::filter_map(data, |data| data.downcast_mut()).ok()?,
-            borrow: &self.borrow,
-            _guard: guard,
-        })
+            .get(&TypeId::of::<T>())
+            .map(|c| c.try_borrow())
+            .transpose()?
+            .and_then(|data| Ref::filter_map(data, |data| data.downcast_ref()).ok());
+        match data {
+            Some(data) => {
+                self.borrow.set(self.borrow.get() + 1);
+                Ok(Some(AppDataRef {
+                    data,
+                    borrow: &self.borrow,
+                    _guard: guard,
+                }))
+            }
+            None => Ok(None),
+        }
+    }
+
+    #[inline]
+    #[track_caller]
+    pub(crate) fn borrow_mut<T: 'static>(&self, guard: Option<LuaGuard>) -> Option<AppDataRefMut<'_, T>> {
+        match self.try_borrow_mut(guard) {
+            Ok(data) => data,
+            Err(err) => panic!("already borrowed: {err:?}"),
+        }
+    }
+
+    pub(crate) fn try_borrow_mut<T: 'static>(
+        &self,
+        guard: Option<LuaGuard>,
+    ) -> Result<Option<AppDataRefMut<'_, T>>, BorrowMutError> {
+        let data = unsafe { &*self.container.get() }
+            .get(&TypeId::of::<T>())
+            .map(|c| c.try_borrow_mut())
+            .transpose()?
+            .and_then(|data| RefMut::filter_map(data, |data| data.downcast_mut()).ok());
+        match data {
+            Some(data) => {
+                self.borrow.set(self.borrow.get() + 1);
+                Ok(Some(AppDataRefMut {
+                    data,
+                    borrow: &self.borrow,
+                    _guard: guard,
+                }))
+            }
+            None => Ok(None),
+        }
     }
 
     #[track_caller]

src/types/registry_key.rs

@@ -12,17 +12,16 @@ use parking_lot::Mutex;
 /// and instances not manually removed can be garbage collected with
 /// [`Lua::expire_registry_values`].
 ///
-/// Be warned, If you place this into Lua via a [`UserData`] type or a rust callback, it is *very
-/// easy* to accidentally cause reference cycles that the Lua garbage collector cannot resolve.
-/// Instead of placing a [`RegistryKey`] into a [`UserData`] type, prefer instead to use
-/// [`AnyUserData::set_user_value`] / [`AnyUserData::user_value`].
+/// Be warned, If you place this into Lua via a [`UserData`] type or a Rust callback, it is *easy*
+/// to accidentally cause reference cycles that the Lua garbage collector cannot resolve. Instead of
+/// placing a [`RegistryKey`] into a [`UserData`] type, consider to use
+/// [`AnyUserData::set_user_value`].
 ///
 /// [`UserData`]: crate::UserData
 /// [`RegistryKey`]: crate::RegistryKey
 /// [`Lua::remove_registry_value`]: crate::Lua::remove_registry_value
 /// [`Lua::expire_registry_values`]: crate::Lua::expire_registry_values
 /// [`AnyUserData::set_user_value`]: crate::AnyUserData::set_user_value
-/// [`AnyUserData::user_value`]: crate::AnyUserData::user_value
 pub struct RegistryKey {
     pub(crate) registry_id: i32,
     pub(crate) unref_list: Arc<Mutex<Option<Vec<c_int>>>>,

src/types/sync.rs

@@ -31,7 +31,7 @@ mod inner {
         }
 
         #[inline(always)]
-        pub(crate) fn lock(&self) -> ReentrantMutexGuard<T> {
+        pub(crate) fn lock(&self) -> ReentrantMutexGuard<'_, T> {
             ReentrantMutexGuard(&self.0)
         }
 
@@ -53,7 +53,7 @@ mod inner {
 
     pub(crate) struct ReentrantMutexGuard<'a, T>(&'a T);
 
-    impl<'a, T> Deref for ReentrantMutexGuard<'a, T> {
+    impl<T> Deref for ReentrantMutexGuard<'_, T> {
         type Target = T;
 
         #[inline(always)]

src/types/value_ref.rs

@@ -0,0 +1,71 @@
+use std::fmt;
+use std::os::raw::{c_int, c_void};
+
+use crate::state::{RawLua, WeakLua};
+
+/// A reference to a Lua (complex) value stored in the Lua auxiliary thread.
+pub struct ValueRef {
+    pub(crate) lua: WeakLua,
+    pub(crate) index: c_int,
+    pub(crate) drop: bool,
+}
+
+impl ValueRef {
+    #[inline]
+    pub(crate) fn new(lua: &RawLua, index: c_int) -> Self {
+        ValueRef {
+            lua: lua.weak().clone(),
+            index,
+            drop: true,
+        }
+    }
+
+    #[inline]
+    pub(crate) fn to_pointer(&self) -> *const c_void {
+        let lua = self.lua.lock();
+        unsafe { ffi::lua_topointer(lua.ref_thread(), self.index) }
+    }
+
+    /// Returns a copy of the value, which is valid as long as the original value is held.
+    #[inline]
+    pub(crate) fn copy(&self) -> Self {
+        ValueRef {
+            lua: self.lua.clone(),
+            index: self.index,
+            drop: false,
+        }
+    }
+}
+
+impl fmt::Debug for ValueRef {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "Ref({:p})", self.to_pointer())
+    }
+}
+
+impl Clone for ValueRef {
+    fn clone(&self) -> Self {
+        unsafe { self.lua.lock().clone_ref(self) }
+    }
+}
+
+impl Drop for ValueRef {
+    fn drop(&mut self) {
+        if self.drop {
+            if let Some(lua) = self.lua.try_lock() {
+                unsafe { lua.drop_ref(self) };
+            }
+        }
+    }
+}
+
+impl PartialEq for ValueRef {
+    fn eq(&self, other: &Self) -> bool {
+        assert!(
+            self.lua == other.lua,
+            "Lua instance passed Value created from a different main Lua state"
+        );
+        let lua = self.lua.lock();
+        unsafe { ffi::lua_rawequal(lua.ref_thread(), self.index, other.index) == 1 }
+    }
+}

src/userdata/cell.rs

@@ -1,33 +1,31 @@
-use std::any::{type_name, TypeId};
-use std::cell::UnsafeCell;
-use std::fmt;
-use std::ops::{Deref, DerefMut};
-use std::os::raw::c_int;
+use std::cell::{RefCell, UnsafeCell};
 
-#[cfg(feature = "serialize")]
+#[cfg(feature = "serde")]
 use serde::ser::{Serialize, Serializer};
 
 use crate::error::{Error, Result};
-use crate::state::{Lua, RawLua};
-use crate::types::{MaybeSend, XRc};
-use crate::userdata::AnyUserData;
-use crate::util::get_userdata;
-use crate::value::{FromLua, Value};
+use crate::types::XRc;
 
 use super::lock::{RawLock, UserDataLock};
+use super::r#ref::{UserDataRef, UserDataRefMut};
 
-#[cfg(all(feature = "serialize", not(feature = "send")))]
+#[cfg(all(feature = "serde", not(feature = "send")))]
 type DynSerialize = dyn erased_serde::Serialize;
 
-#[cfg(all(feature = "serialize", feature = "send"))]
+#[cfg(all(feature = "serde", feature = "send"))]
 type DynSerialize = dyn erased_serde::Serialize + Send;
 
+pub(crate) enum UserDataStorage<T> {
+    Owned(UserDataVariant<T>),
+    Scoped(ScopedUserDataVariant<T>),
+}
+
 // A enum for storing userdata values.
 // It's stored inside a Lua VM and protected by the outer `ReentrantMutex`.
 pub(crate) enum UserDataVariant<T> {
     Default(XRc<UserDataCell<T>>),
-    #[cfg(feature = "serialize")]
-    Serializable(XRc<UserDataCell<Box<DynSerialize>>>),
+    #[cfg(feature = "serde")]
+    Serializable(XRc<UserDataCell<Box<DynSerialize>>>, bool), // bool is `is_sync`
 }
 
 impl<T> Clone for UserDataVariant<T> {
@@ -35,53 +33,54 @@ impl<T> Clone for UserDataVariant<T> {
     fn clone(&self) -> Self {
         match self {
             Self::Default(inner) => Self::Default(XRc::clone(inner)),
-            #[cfg(feature = "serialize")]
-            Self::Serializable(inner) => Self::Serializable(XRc::clone(inner)),
+            #[cfg(feature = "serde")]
+            Self::Serializable(inner, is_sync) => Self::Serializable(XRc::clone(inner), *is_sync),
         }
     }
 }
 
 impl<T> UserDataVariant<T> {
     #[inline(always)]
-    pub(crate) fn new(data: T) -> Self {
-        Self::Default(XRc::new(UserDataCell::new(data)))
-    }
-
-    // Immutably borrows the wrapped value in-place.
-    #[inline(always)]
-    pub(crate) fn try_borrow(&self) -> Result<UserDataBorrowRef<T>> {
-        UserDataBorrowRef::try_from(self)
-    }
-
-    // Immutably borrows the wrapped value and returns an owned reference.
-    #[inline(always)]
-    pub(crate) fn try_borrow_owned(&self) -> Result<UserDataRef<T>> {
-        UserDataRef::try_from(self.clone())
+    pub(super) fn try_borrow_scoped<R>(&self, f: impl FnOnce(&T) -> R) -> Result<R> {
+        // We don't need to check for `T: Sync` because when this method is used (internally),
+        // Lua mutex is already locked.
+        // If non-`Sync` userdata is already borrowed by another thread (via `UserDataRef`), it will be
+        // exclusively locked.
+        let _guard = (self.raw_lock().try_lock_shared_guarded()).map_err(|_| Error::UserDataBorrowError)?;
+        Ok(f(unsafe { &*self.as_ptr() }))
     }
 
     // Mutably borrows the wrapped value in-place.
     #[inline(always)]
-    pub(crate) fn try_borrow_mut(&self) -> Result<UserDataBorrowMut<T>> {
-        UserDataBorrowMut::try_from(self)
+    fn try_borrow_scoped_mut<R>(&self, f: impl FnOnce(&mut T) -> R) -> Result<R> {
+        let _guard =
+            (self.raw_lock().try_lock_exclusive_guarded()).map_err(|_| Error::UserDataBorrowMutError)?;
+        Ok(f(unsafe { &mut *self.as_ptr() }))
+    }
+
+    // Immutably borrows the wrapped value and returns an owned reference.
+    #[inline(always)]
+    fn try_borrow_owned(&self) -> Result<UserDataRef<T>> {
+        UserDataRef::try_from(self.clone())
     }
 
     // Mutably borrows the wrapped value and returns an owned reference.
     #[inline(always)]
-    pub(crate) fn try_borrow_owned_mut(&self) -> Result<UserDataRefMut<T>> {
+    fn try_borrow_owned_mut(&self) -> Result<UserDataRefMut<T>> {
         UserDataRefMut::try_from(self.clone())
     }
 
     // Returns the wrapped value.
     //
     // This method checks that we have exclusive access to the value.
-    pub(crate) fn into_inner(self) -> Result<T> {
+    fn into_inner(self) -> Result<T> {
         if !self.raw_lock().try_lock_exclusive() {
             return Err(Error::UserDataBorrowMutError);
         }
         Ok(match self {
             Self::Default(inner) => XRc::into_inner(inner).unwrap().value.into_inner(),
-            #[cfg(feature = "serialize")]
-            Self::Serializable(inner) => unsafe {
+            #[cfg(feature = "serde")]
+            Self::Serializable(inner, _) => unsafe {
                 let raw = Box::into_raw(XRc::into_inner(inner).unwrap().value.into_inner());
                 *Box::from_raw(raw as *mut T)
             },
@@ -89,47 +88,57 @@ impl<T> UserDataVariant<T> {
     }
 
     #[inline(always)]
-    fn raw_lock(&self) -> &RawLock {
+    fn strong_count(&self) -> usize {
+        match self {
+            Self::Default(inner) => XRc::strong_count(inner),
+            #[cfg(feature = "serde")]
+            Self::Serializable(inner, _) => XRc::strong_count(inner),
+        }
+    }
+
+    #[inline(always)]
+    pub(super) fn raw_lock(&self) -> &RawLock {
         match self {
             Self::Default(inner) => &inner.raw_lock,
-            #[cfg(feature = "serialize")]
-            Self::Serializable(inner) => &inner.raw_lock,
+            #[cfg(feature = "serde")]
+            Self::Serializable(inner, _) => &inner.raw_lock,
         }
     }
 
     #[inline(always)]
-    fn as_ptr(&self) -> *mut T {
+    pub(super) fn as_ptr(&self) -> *mut T {
         match self {
             Self::Default(inner) => inner.value.get(),
-            #[cfg(feature = "serialize")]
-            Self::Serializable(inner) => unsafe { &mut **(inner.value.get() as *mut Box<T>) },
+            #[cfg(feature = "serde")]
+            Self::Serializable(inner, _) => unsafe { &mut **(inner.value.get() as *mut Box<T>) },
         }
     }
 }
 
-#[cfg(feature = "serialize")]
-impl<T: Serialize + MaybeSend + 'static> UserDataVariant<T> {
-    #[inline(always)]
-    pub(crate) fn new_ser(data: T) -> Self {
-        let data = Box::new(data) as Box<DynSerialize>;
-        Self::Serializable(XRc::new(UserDataCell::new(data)))
-    }
-}
-
-#[cfg(feature = "serialize")]
-impl Serialize for UserDataVariant<()> {
+#[cfg(feature = "serde")]
+impl Serialize for UserDataStorage<()> {
     fn serialize<S: Serializer>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error> {
         match self {
-            Self::Default(_) => Err(serde::ser::Error::custom("cannot serialize <userdata>")),
-            Self::Serializable(inner) => unsafe {
-                // We need to borrow the inner value exclusively to serialize it.
+            Self::Owned(variant @ UserDataVariant::Serializable(inner, is_sync)) => unsafe {
                 #[cfg(feature = "send")]
-                let _guard = self.try_borrow_mut().map_err(serde::ser::Error::custom)?;
-                // No need to do this if the `send` feature is disabled.
+                if *is_sync {
+                    let _guard = (variant.raw_lock().try_lock_shared_guarded())
+                        .map_err(|_| serde::ser::Error::custom(Error::UserDataBorrowError))?;
+                    (*inner.value.get()).serialize(serializer)
+                } else {
+                    let _guard = (variant.raw_lock().try_lock_exclusive_guarded())
+                        .map_err(|_| serde::ser::Error::custom(Error::UserDataBorrowError))?;
+                    (*inner.value.get()).serialize(serializer)
+                }
                 #[cfg(not(feature = "send"))]
-                let _guard = self.try_borrow().map_err(serde::ser::Error::custom)?;
-                (*inner.value.get()).serialize(serializer)
+                {
+                    let _ = is_sync;
+                    let _guard = (variant.raw_lock().try_lock_shared_guarded())
+                        .map_err(|_| serde::ser::Error::custom(Error::UserDataBorrowError))?;
+                    (*inner.value.get()).serialize(serializer)
+                }
             },
+            _ => Err(serde::ser::Error::custom("cannot serialize <userdata>")),
         }
     }
 }
@@ -140,12 +149,14 @@ pub(crate) struct UserDataCell<T> {
     value: UnsafeCell<T>,
 }
 
+#[cfg(feature = "send")]
 unsafe impl<T: Send> Send for UserDataCell<T> {}
+#[cfg(feature = "send")]
 unsafe impl<T: Send> Sync for UserDataCell<T> {}
 
 impl<T> UserDataCell<T> {
     #[inline(always)]
-    pub fn new(value: T) -> Self {
+    fn new(value: T) -> Self {
         UserDataCell {
             raw_lock: RawLock::INIT,
             value: UnsafeCell::new(value),
@@ -153,239 +164,135 @@ impl<T> UserDataCell<T> {
     }
 }
 
-/// A wrapper type for a [`UserData`] value that provides read access.
-///
-/// It implements [`FromLua`] and can be used to receive a typed userdata from Lua.
-pub struct UserDataRef<T>(UserDataVariant<T>);
-
-impl<T> Deref for UserDataRef<T> {
-    type Target = T;
-
-    #[inline]
-    fn deref(&self) -> &T {
-        unsafe { &*self.0.as_ptr() }
-    }
+pub(crate) enum ScopedUserDataVariant<T> {
+    Ref(*const T),
+    RefMut(RefCell<*mut T>),
+    Boxed(RefCell<*mut T>),
 }
 
-impl<T> Drop for UserDataRef<T> {
+impl<T> Drop for ScopedUserDataVariant<T> {
     #[inline]
     fn drop(&mut self) {
-        unsafe { self.0.raw_lock().unlock_shared() };
-    }
-}
-
-impl<T: fmt::Debug> fmt::Debug for UserDataRef<T> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        (**self).fmt(f)
-    }
-}
-
-impl<T: fmt::Display> fmt::Display for UserDataRef<T> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        (**self).fmt(f)
-    }
-}
-
-impl<T> TryFrom<UserDataVariant<T>> for UserDataRef<T> {
-    type Error = Error;
-
-    #[inline]
-    fn try_from(variant: UserDataVariant<T>) -> Result<Self> {
-        if !variant.raw_lock().try_lock_shared() {
-            return Err(Error::UserDataBorrowError);
-        }
-        Ok(UserDataRef(variant))
-    }
-}
-
-impl<T: 'static> FromLua for UserDataRef<T> {
-    fn from_lua(value: Value, _: &Lua) -> Result<Self> {
-        try_value_to_userdata::<T>(value)?.borrow()
-    }
-
-    unsafe fn from_stack(idx: c_int, lua: &RawLua) -> Result<Self> {
-        let type_id = lua.get_userdata_type_id(idx)?;
-        match type_id {
-            Some(type_id) if type_id == TypeId::of::<T>() => {
-                (*get_userdata::<UserDataVariant<T>>(lua.state(), idx)).try_borrow_owned()
+        if let Self::Boxed(value) = self {
+            if let Ok(value) = value.try_borrow_mut() {
+                unsafe { drop(Box::from_raw(*value)) };
             }
-            _ => Err(Error::UserDataTypeMismatch),
         }
     }
 }
 
-/// A wrapper type for a mutably borrowed value from a `AnyUserData`.
-///
-/// It implements [`FromLua`] and can be used to receive a typed userdata from Lua.
-pub struct UserDataRefMut<T>(UserDataVariant<T>);
-
-impl<T> Deref for UserDataRefMut<T> {
-    type Target = T;
-
-    #[inline]
-    fn deref(&self) -> &Self::Target {
-        unsafe { &*self.0.as_ptr() }
+impl<T: 'static> UserDataStorage<T> {
+    #[inline(always)]
+    pub(crate) fn new(data: T) -> Self {
+        Self::Owned(UserDataVariant::Default(XRc::new(UserDataCell::new(data))))
     }
-}
-
-impl<T> DerefMut for UserDataRefMut<T> {
-    #[inline]
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        unsafe { &mut *self.0.as_ptr() }
-    }
-}
-
-impl<T> Drop for UserDataRefMut<T> {
-    #[inline]
-    fn drop(&mut self) {
-        unsafe { self.0.raw_lock().unlock_exclusive() };
-    }
-}
-
-impl<T: fmt::Debug> fmt::Debug for UserDataRefMut<T> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        (**self).fmt(f)
-    }
-}
-
-impl<T: fmt::Display> fmt::Display for UserDataRefMut<T> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        (**self).fmt(f)
-    }
-}
-
-impl<T> TryFrom<UserDataVariant<T>> for UserDataRefMut<T> {
-    type Error = Error;
-
-    #[inline]
-    fn try_from(variant: UserDataVariant<T>) -> Result<Self> {
-        if !variant.raw_lock().try_lock_exclusive() {
-            return Err(Error::UserDataBorrowMutError);
-        }
-        Ok(UserDataRefMut(variant))
-    }
-}
-
-impl<T: 'static> FromLua for UserDataRefMut<T> {
-    fn from_lua(value: Value, _: &Lua) -> Result<Self> {
-        try_value_to_userdata::<T>(value)?.borrow_mut()
-    }
-
-    unsafe fn from_stack(idx: c_int, lua: &RawLua) -> Result<Self> {
-        let type_id = lua.get_userdata_type_id(idx)?;
-        match type_id {
-            Some(type_id) if type_id == TypeId::of::<T>() => {
-                (*get_userdata::<UserDataVariant<T>>(lua.state(), idx)).try_borrow_owned_mut()
-            }
-            _ => Err(Error::UserDataTypeMismatch),
-        }
-    }
-}
-
-/// A type that provides read access to a userdata value (borrowing the value).
-pub(crate) struct UserDataBorrowRef<'a, T>(&'a UserDataVariant<T>);
-
-impl<'a, T> Drop for UserDataBorrowRef<'a, T> {
-    #[inline]
-    fn drop(&mut self) {
-        unsafe { self.0.raw_lock().unlock_shared() };
-    }
-}
-
-impl<'a, T> Deref for UserDataBorrowRef<'a, T> {
-    type Target = T;
-
-    #[inline]
-    fn deref(&self) -> &T {
-        // SAFETY: `UserDataBorrowRef` is only created with shared access to the value.
-        unsafe { &*self.0.as_ptr() }
-    }
-}
-
-impl<'a, T> TryFrom<&'a UserDataVariant<T>> for UserDataBorrowRef<'a, T> {
-    type Error = Error;
 
     #[inline(always)]
-    fn try_from(variant: &'a UserDataVariant<T>) -> Result<Self> {
-        if !variant.raw_lock().try_lock_shared() {
-            return Err(Error::UserDataBorrowError);
-        }
-        Ok(UserDataBorrowRef(variant))
+    pub(crate) fn new_ref(data: &T) -> Self {
+        Self::Scoped(ScopedUserDataVariant::Ref(data))
     }
-}
-
-pub(crate) struct UserDataBorrowMut<'a, T>(&'a UserDataVariant<T>);
-
-impl<'a, T> Drop for UserDataBorrowMut<'a, T> {
-    #[inline]
-    fn drop(&mut self) {
-        unsafe { self.0.raw_lock().unlock_exclusive() };
-    }
-}
-
-impl<'a, T> Deref for UserDataBorrowMut<'a, T> {
-    type Target = T;
-
-    #[inline]
-    fn deref(&self) -> &T {
-        unsafe { &*self.0.as_ptr() }
-    }
-}
-
-impl<'a, T> DerefMut for UserDataBorrowMut<'a, T> {
-    #[inline]
-    fn deref_mut(&mut self) -> &mut T {
-        unsafe { &mut *self.0.as_ptr() }
-    }
-}
-
-impl<'a, T> TryFrom<&'a UserDataVariant<T>> for UserDataBorrowMut<'a, T> {
-    type Error = Error;
 
     #[inline(always)]
-    fn try_from(variant: &'a UserDataVariant<T>) -> Result<Self> {
-        if !variant.raw_lock().try_lock_exclusive() {
-            return Err(Error::UserDataBorrowMutError);
+    pub(crate) fn new_ref_mut(data: &mut T) -> Self {
+        Self::Scoped(ScopedUserDataVariant::RefMut(RefCell::new(data)))
+    }
+
+    #[cfg(feature = "serde")]
+    #[inline(always)]
+    pub(crate) fn new_ser(data: T) -> Self
+    where
+        T: Serialize + crate::types::MaybeSend,
+    {
+        let data = Box::new(data) as Box<DynSerialize>;
+        let is_sync = super::util::is_sync::<T>();
+        let variant = UserDataVariant::Serializable(XRc::new(UserDataCell::new(data)), is_sync);
+        Self::Owned(variant)
+    }
+
+    #[cfg(feature = "serde")]
+    #[inline(always)]
+    pub(crate) fn is_serializable(&self) -> bool {
+        matches!(self, Self::Owned(UserDataVariant::Serializable(..)))
+    }
+
+    // Immutably borrows the wrapped value and returns an owned reference.
+    #[inline(always)]
+    pub(crate) fn try_borrow_owned(&self) -> Result<UserDataRef<T>> {
+        match self {
+            Self::Owned(data) => data.try_borrow_owned(),
+            Self::Scoped(_) => Err(Error::UserDataTypeMismatch),
+        }
+    }
+
+    // Mutably borrows the wrapped value and returns an owned reference.
+    #[inline(always)]
+    pub(crate) fn try_borrow_owned_mut(&self) -> Result<UserDataRefMut<T>> {
+        match self {
+            Self::Owned(data) => data.try_borrow_owned_mut(),
+            Self::Scoped(_) => Err(Error::UserDataTypeMismatch),
+        }
+    }
+
+    #[inline(always)]
+    pub(crate) fn into_inner(self) -> Result<T> {
+        match self {
+            Self::Owned(data) => data.into_inner(),
+            Self::Scoped(_) => Err(Error::UserDataTypeMismatch),
         }
-        Ok(UserDataBorrowMut(variant))
     }
 }
 
-#[inline]
-fn try_value_to_userdata<T>(value: Value) -> Result<AnyUserData> {
-    match value {
-        Value::UserData(ud) => Ok(ud),
-        _ => Err(Error::FromLuaConversionError {
-            from: value.type_name(),
-            to: "userdata",
-            message: Some(format!("expected userdata of type {}", type_name::<T>())),
-        }),
+impl<T> UserDataStorage<T> {
+    #[inline(always)]
+    pub(crate) fn new_scoped(data: T) -> Self {
+        let data = Box::into_raw(Box::new(data));
+        Self::Scoped(ScopedUserDataVariant::Boxed(RefCell::new(data)))
+    }
+
+    /// Returns `true` if it's safe to destroy the container.
+    ///
+    /// It's safe to destroy the container if the reference count is greater than 1 or the lock is
+    /// not acquired.
+    #[inline(always)]
+    pub(crate) fn is_safe_to_destroy(&self) -> bool {
+        match self {
+            Self::Owned(variant) => variant.strong_count() > 1 || !variant.raw_lock().is_locked(),
+            Self::Scoped(_) => false,
+        }
+    }
+
+    /// Returns `true` if the container has exclusive access to the value.
+    #[inline(always)]
+    pub(crate) fn has_exclusive_access(&self) -> bool {
+        match self {
+            Self::Owned(variant) => !variant.raw_lock().is_locked(),
+            Self::Scoped(_) => false,
+        }
+    }
+
+    #[inline]
+    pub(crate) fn try_borrow_scoped<R>(&self, f: impl FnOnce(&T) -> R) -> Result<R> {
+        match self {
+            Self::Owned(data) => data.try_borrow_scoped(f),
+            Self::Scoped(ScopedUserDataVariant::Ref(value)) => Ok(f(unsafe { &**value })),
+            Self::Scoped(ScopedUserDataVariant::RefMut(value) | ScopedUserDataVariant::Boxed(value)) => {
+                let t = value.try_borrow().map_err(|_| Error::UserDataBorrowError)?;
+                Ok(f(unsafe { &**t }))
+            }
+        }
+    }
+
+    #[inline]
+    pub(crate) fn try_borrow_scoped_mut<R>(&self, f: impl FnOnce(&mut T) -> R) -> Result<R> {
+        match self {
+            Self::Owned(data) => data.try_borrow_scoped_mut(f),
+            Self::Scoped(ScopedUserDataVariant::Ref(_)) => Err(Error::UserDataBorrowMutError),
+            Self::Scoped(ScopedUserDataVariant::RefMut(value) | ScopedUserDataVariant::Boxed(value)) => {
+                let mut t = value
+                    .try_borrow_mut()
+                    .map_err(|_| Error::UserDataBorrowMutError)?;
+                Ok(f(unsafe { &mut **t }))
+            }
+        }
     }
 }
-
-#[cfg(test)]
-mod assertions {
-    use super::*;
-
-    #[cfg(feature = "send")]
-    static_assertions::assert_impl_all!(UserDataRef<()>: Send, Sync);
-    #[cfg(feature = "send")]
-    static_assertions::assert_not_impl_all!(UserDataRef<std::rc::Rc<()>>: Send, Sync);
-    #[cfg(feature = "send")]
-    static_assertions::assert_impl_all!(UserDataRefMut<()>: Sync, Send);
-    #[cfg(feature = "send")]
-    static_assertions::assert_not_impl_all!(UserDataRefMut<std::rc::Rc<()>>: Send, Sync);
-    #[cfg(feature = "send")]
-    static_assertions::assert_impl_all!(UserDataBorrowRef<'_, ()>: Send, Sync);
-    #[cfg(feature = "send")]
-    static_assertions::assert_impl_all!(UserDataBorrowMut<'_, ()>: Send, Sync);
-
-    #[cfg(not(feature = "send"))]
-    static_assertions::assert_not_impl_all!(UserDataRef<()>: Send, Sync);
-    #[cfg(not(feature = "send"))]
-    static_assertions::assert_not_impl_all!(UserDataRefMut<()>: Send, Sync);
-    #[cfg(not(feature = "send"))]
-    static_assertions::assert_not_impl_all!(UserDataBorrowRef<'_, ()>: Send, Sync);
-    #[cfg(not(feature = "send"))]
-    static_assertions::assert_not_impl_all!(UserDataBorrowMut<'_, ()>: Send, Sync);
-}

src/userdata/lock.rs

@@ -1,16 +1,57 @@
 pub(crate) trait UserDataLock {
     const INIT: Self;
 
+    fn is_locked(&self) -> bool;
     fn try_lock_shared(&self) -> bool;
     fn try_lock_exclusive(&self) -> bool;
 
     unsafe fn unlock_shared(&self);
     unsafe fn unlock_exclusive(&self);
+
+    fn try_lock_shared_guarded(&self) -> Result<LockGuard<'_, Self>, ()> {
+        if self.try_lock_shared() {
+            Ok(LockGuard {
+                lock: self,
+                exclusive: false,
+            })
+        } else {
+            Err(())
+        }
+    }
+
+    fn try_lock_exclusive_guarded(&self) -> Result<LockGuard<'_, Self>, ()> {
+        if self.try_lock_exclusive() {
+            Ok(LockGuard {
+                lock: self,
+                exclusive: true,
+            })
+        } else {
+            Err(())
+        }
+    }
+}
+
+pub(crate) struct LockGuard<'a, L: UserDataLock + ?Sized> {
+    lock: &'a L,
+    exclusive: bool,
+}
+
+impl<L: UserDataLock + ?Sized> Drop for LockGuard<'_, L> {
+    fn drop(&mut self) {
+        unsafe {
+            if self.exclusive {
+                self.lock.unlock_exclusive();
+            } else {
+                self.lock.unlock_shared();
+            }
+        }
+    }
 }
 
 pub(crate) use lock_impl::RawLock;
 
 #[cfg(not(feature = "send"))]
+#[cfg(not(tarpaulin_include))]
 mod lock_impl {
     use std::cell::Cell;
 
@@ -24,6 +65,11 @@ mod lock_impl {
         #[allow(clippy::declare_interior_mutable_const)]
         const INIT: Self = Cell::new(UNUSED);
 
+        #[inline(always)]
+        fn is_locked(&self) -> bool {
+            self.get() != UNUSED
+        }
+
         #[inline(always)]
         fn try_lock_shared(&self) -> bool {
             let flag = self.get().wrapping_add(1);
@@ -62,32 +108,37 @@ mod lock_impl {
 
 #[cfg(feature = "send")]
 mod lock_impl {
-    use parking_lot::lock_api::RawMutex;
+    use parking_lot::lock_api::RawRwLock;
 
-    pub(crate) type RawLock = parking_lot::RawMutex;
+    pub(crate) type RawLock = parking_lot::RawRwLock;
 
     impl super::UserDataLock for RawLock {
         #[allow(clippy::declare_interior_mutable_const)]
-        const INIT: Self = <Self as parking_lot::lock_api::RawMutex>::INIT;
+        const INIT: Self = <Self as parking_lot::lock_api::RawRwLock>::INIT;
+
+        #[inline(always)]
+        fn is_locked(&self) -> bool {
+            RawRwLock::is_locked(self)
+        }
 
         #[inline(always)]
         fn try_lock_shared(&self) -> bool {
-            RawLock::try_lock(self)
+            RawRwLock::try_lock_shared(self)
         }
 
         #[inline(always)]
         fn try_lock_exclusive(&self) -> bool {
-            RawLock::try_lock(self)
+            RawRwLock::try_lock_exclusive(self)
         }
 
         #[inline(always)]
         unsafe fn unlock_shared(&self) {
-            RawLock::unlock(self)
+            RawRwLock::unlock_shared(self)
         }
 
         #[inline(always)]
         unsafe fn unlock_exclusive(&self) {
-            RawLock::unlock(self)
+            RawRwLock::unlock_exclusive(self)
         }
     }
 }

src/userdata/object.rs

@@ -2,13 +2,13 @@ use std::string::String as StdString;
 
 use crate::error::{Error, Result};
 use crate::table::Table;
-use crate::traits::ObjectLike;
+use crate::traits::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, ObjectLike};
 use crate::userdata::AnyUserData;
-use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, Value};
+use crate::value::Value;
 use crate::Function;
 
 #[cfg(feature = "async")]
-use futures_util::future::{self, Either, Future};
+use crate::function::AsyncCallFuture;
 
 impl ObjectLike for AnyUserData {
     #[inline]
@@ -35,7 +35,7 @@ impl ObjectLike for AnyUserData {
 
     #[cfg(feature = "async")]
     #[inline]
-    fn call_async<R>(&self, args: impl IntoLuaMulti) -> impl Future<Output = Result<R>>
+    fn call_async<R>(&self, args: impl IntoLuaMulti) -> AsyncCallFuture<R>
     where
         R: FromLuaMulti,
     {
@@ -51,7 +51,7 @@ impl ObjectLike for AnyUserData {
     }
 
     #[cfg(feature = "async")]
-    fn call_async_method<R>(&self, name: &str, args: impl IntoLuaMulti) -> impl Future<Output = Result<R>>
+    fn call_async_method<R>(&self, name: &str, args: impl IntoLuaMulti) -> AsyncCallFuture<R>
     where
         R: FromLuaMulti,
     {
@@ -72,22 +72,22 @@ impl ObjectLike for AnyUserData {
     }
 
     #[cfg(feature = "async")]
-    fn call_async_function<R>(&self, name: &str, args: impl IntoLuaMulti) -> impl Future<Output = Result<R>>
+    fn call_async_function<R>(&self, name: &str, args: impl IntoLuaMulti) -> AsyncCallFuture<R>
     where
         R: FromLuaMulti,
     {
         match self.get(name) {
-            Ok(Value::Function(func)) => Either::Left(func.call_async(args)),
+            Ok(Value::Function(func)) => func.call_async(args),
             Ok(val) => {
                 let msg = format!("attempt to call a {} value (function '{name}')", val.type_name());
-                Either::Right(future::ready(Err(Error::RuntimeError(msg))))
+                AsyncCallFuture::error(Error::RuntimeError(msg))
             }
-            Err(err) => Either::Right(future::ready(Err(err))),
+            Err(err) => AsyncCallFuture::error(err),
         }
     }
 
     #[inline]
     fn to_string(&self) -> Result<StdString> {
-        Value::UserData(AnyUserData(self.0.copy(), self.1)).to_string()
+        Value::UserData(AnyUserData(self.0.copy())).to_string()
     }
 }

src/userdata/ref.rs

@@ -0,0 +1,474 @@
+use std::any::{type_name, TypeId};
+use std::ops::{Deref, DerefMut};
+use std::os::raw::c_int;
+use std::{fmt, mem};
+
+use crate::error::{Error, Result};
+use crate::state::{Lua, RawLua};
+use crate::traits::FromLua;
+use crate::userdata::AnyUserData;
+use crate::util::get_userdata;
+use crate::value::Value;
+
+use super::cell::{UserDataStorage, UserDataVariant};
+use super::lock::{LockGuard, RawLock, UserDataLock};
+use super::util::is_sync;
+
+#[cfg(feature = "userdata-wrappers")]
+use {
+    parking_lot::{
+        Mutex as MutexPL, MutexGuard as MutexGuardPL, RwLock as RwLockPL,
+        RwLockReadGuard as RwLockReadGuardPL, RwLockWriteGuard as RwLockWriteGuardPL,
+    },
+    std::sync::Arc,
+};
+#[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+use {
+    std::cell::{Ref, RefCell, RefMut},
+    std::rc::Rc,
+};
+
+/// A wrapper type for a userdata value that provides read access.
+///
+/// It implements [`FromLua`] and can be used to receive a typed userdata from Lua.
+pub struct UserDataRef<T: 'static> {
+    // It's important to drop the guard first, as it refers to the `inner` data.
+    _guard: LockGuard<'static, RawLock>,
+    inner: UserDataRefInner<T>,
+}
+
+impl<T> Deref for UserDataRef<T> {
+    type Target = T;
+
+    #[inline]
+    fn deref(&self) -> &T {
+        &self.inner
+    }
+}
+
+impl<T: fmt::Debug> fmt::Debug for UserDataRef<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
+impl<T: fmt::Display> fmt::Display for UserDataRef<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
+impl<T> TryFrom<UserDataVariant<T>> for UserDataRef<T> {
+    type Error = Error;
+
+    #[inline]
+    fn try_from(variant: UserDataVariant<T>) -> Result<Self> {
+        let guard = if cfg!(not(feature = "send")) || is_sync::<T>() {
+            variant.raw_lock().try_lock_shared_guarded()
+        } else {
+            variant.raw_lock().try_lock_exclusive_guarded()
+        };
+        let guard = guard.map_err(|_| Error::UserDataBorrowError)?;
+        let guard = unsafe { mem::transmute::<LockGuard<_>, LockGuard<'static, _>>(guard) };
+        Ok(UserDataRef::from_parts(UserDataRefInner::Default(variant), guard))
+    }
+}
+
+impl<T: 'static> FromLua for UserDataRef<T> {
+    fn from_lua(value: Value, _: &Lua) -> Result<Self> {
+        try_value_to_userdata::<T>(value)?.borrow()
+    }
+
+    #[inline]
+    unsafe fn from_stack(idx: c_int, lua: &RawLua) -> Result<Self> {
+        Self::borrow_from_stack(lua, lua.state(), idx)
+    }
+}
+
+impl<T: 'static> UserDataRef<T> {
+    #[inline(always)]
+    fn from_parts(inner: UserDataRefInner<T>, guard: LockGuard<'static, RawLock>) -> Self {
+        Self { _guard: guard, inner }
+    }
+
+    #[cfg(feature = "userdata-wrappers")]
+    fn remap<U>(
+        self,
+        f: impl FnOnce(UserDataVariant<T>) -> Result<UserDataRefInner<U>>,
+    ) -> Result<UserDataRef<U>> {
+        match &self.inner {
+            UserDataRefInner::Default(variant) => {
+                let inner = f(variant.clone())?;
+                Ok(UserDataRef::from_parts(inner, self._guard))
+            }
+            _ => Err(Error::UserDataTypeMismatch),
+        }
+    }
+
+    pub(crate) unsafe fn borrow_from_stack(
+        lua: &RawLua,
+        state: *mut ffi::lua_State,
+        idx: c_int,
+    ) -> Result<Self> {
+        let type_id = lua.get_userdata_type_id::<T>(state, idx)?;
+        match type_id {
+            Some(type_id) if type_id == TypeId::of::<T>() => {
+                let ud = get_userdata::<UserDataStorage<T>>(state, idx);
+                (*ud).try_borrow_owned()
+            }
+
+            #[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+            Some(type_id) if type_id == TypeId::of::<Rc<T>>() => {
+                let ud = get_userdata::<UserDataStorage<Rc<T>>>(state, idx);
+                ((*ud).try_borrow_owned()).and_then(|ud| ud.transform_rc())
+            }
+            #[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+            Some(type_id) if type_id == TypeId::of::<Rc<RefCell<T>>>() => {
+                let ud = get_userdata::<UserDataStorage<Rc<RefCell<T>>>>(state, idx);
+                ((*ud).try_borrow_owned()).and_then(|ud| ud.transform_rc_refcell())
+            }
+
+            #[cfg(feature = "userdata-wrappers")]
+            Some(type_id) if type_id == TypeId::of::<Arc<T>>() => {
+                let ud = get_userdata::<UserDataStorage<Arc<T>>>(state, idx);
+                ((*ud).try_borrow_owned()).and_then(|ud| ud.transform_arc())
+            }
+            #[cfg(feature = "userdata-wrappers")]
+            Some(type_id) if type_id == TypeId::of::<Arc<MutexPL<T>>>() => {
+                let ud = get_userdata::<UserDataStorage<Arc<MutexPL<T>>>>(state, idx);
+                ((*ud).try_borrow_owned()).and_then(|ud| ud.transform_arc_mutex_pl())
+            }
+            #[cfg(feature = "userdata-wrappers")]
+            Some(type_id) if type_id == TypeId::of::<Arc<RwLockPL<T>>>() => {
+                let ud = get_userdata::<UserDataStorage<Arc<RwLockPL<T>>>>(state, idx);
+                ((*ud).try_borrow_owned()).and_then(|ud| ud.transform_arc_rwlock_pl())
+            }
+            _ => Err(Error::UserDataTypeMismatch),
+        }
+    }
+}
+
+#[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+impl<T> UserDataRef<Rc<T>> {
+    fn transform_rc(self) -> Result<UserDataRef<T>> {
+        self.remap(|variant| Ok(UserDataRefInner::Rc(variant)))
+    }
+}
+
+#[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+impl<T> UserDataRef<Rc<RefCell<T>>> {
+    fn transform_rc_refcell(self) -> Result<UserDataRef<T>> {
+        self.remap(|variant| unsafe {
+            let obj = &*variant.as_ptr();
+            let r#ref = obj.try_borrow().map_err(|_| Error::UserDataBorrowError)?;
+            let borrow = std::mem::transmute::<Ref<T>, Ref<'static, T>>(r#ref);
+            Ok(UserDataRefInner::RcRefCell(borrow, variant))
+        })
+    }
+}
+
+#[cfg(feature = "userdata-wrappers")]
+impl<T> UserDataRef<Arc<T>> {
+    fn transform_arc(self) -> Result<UserDataRef<T>> {
+        self.remap(|variant| Ok(UserDataRefInner::Arc(variant)))
+    }
+}
+
+#[cfg(feature = "userdata-wrappers")]
+impl<T> UserDataRef<Arc<MutexPL<T>>> {
+    fn transform_arc_mutex_pl(self) -> Result<UserDataRef<T>> {
+        self.remap(|variant| unsafe {
+            let obj = &*variant.as_ptr();
+            let guard = obj.try_lock().ok_or(Error::UserDataBorrowError)?;
+            let borrow = std::mem::transmute::<MutexGuardPL<T>, MutexGuardPL<'static, T>>(guard);
+            Ok(UserDataRefInner::ArcMutexPL(borrow, variant))
+        })
+    }
+}
+
+#[cfg(feature = "userdata-wrappers")]
+impl<T> UserDataRef<Arc<RwLockPL<T>>> {
+    fn transform_arc_rwlock_pl(self) -> Result<UserDataRef<T>> {
+        self.remap(|variant| unsafe {
+            let obj = &*variant.as_ptr();
+            let guard = obj.try_read().ok_or(Error::UserDataBorrowError)?;
+            let borrow = std::mem::transmute::<RwLockReadGuardPL<T>, RwLockReadGuardPL<'static, T>>(guard);
+            Ok(UserDataRefInner::ArcRwLockPL(borrow, variant))
+        })
+    }
+}
+
+#[allow(unused)]
+enum UserDataRefInner<T: 'static> {
+    Default(UserDataVariant<T>),
+
+    #[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+    Rc(UserDataVariant<Rc<T>>),
+    #[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+    RcRefCell(Ref<'static, T>, UserDataVariant<Rc<RefCell<T>>>),
+
+    #[cfg(feature = "userdata-wrappers")]
+    Arc(UserDataVariant<Arc<T>>),
+    #[cfg(feature = "userdata-wrappers")]
+    ArcMutexPL(MutexGuardPL<'static, T>, UserDataVariant<Arc<MutexPL<T>>>),
+    #[cfg(feature = "userdata-wrappers")]
+    ArcRwLockPL(RwLockReadGuardPL<'static, T>, UserDataVariant<Arc<RwLockPL<T>>>),
+}
+
+impl<T> Deref for UserDataRefInner<T> {
+    type Target = T;
+
+    #[inline]
+    fn deref(&self) -> &T {
+        match self {
+            Self::Default(inner) => unsafe { &*inner.as_ptr() },
+
+            #[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+            Self::Rc(inner) => unsafe { &*Rc::as_ptr(&*inner.as_ptr()) },
+            #[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+            Self::RcRefCell(x, ..) => x,
+
+            #[cfg(feature = "userdata-wrappers")]
+            Self::Arc(inner) => unsafe { &*Arc::as_ptr(&*inner.as_ptr()) },
+            #[cfg(feature = "userdata-wrappers")]
+            Self::ArcMutexPL(x, ..) => x,
+            #[cfg(feature = "userdata-wrappers")]
+            Self::ArcRwLockPL(x, ..) => x,
+        }
+    }
+}
+
+/// A wrapper type for a userdata value that provides read and write access.
+///
+/// It implements [`FromLua`] and can be used to receive a typed userdata from Lua.
+pub struct UserDataRefMut<T: 'static> {
+    // It's important to drop the guard first, as it refers to the `inner` data.
+    _guard: LockGuard<'static, RawLock>,
+    inner: UserDataRefMutInner<T>,
+}
+
+impl<T> Deref for UserDataRefMut<T> {
+    type Target = T;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &self.inner
+    }
+}
+
+impl<T> DerefMut for UserDataRefMut<T> {
+    #[inline]
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.inner
+    }
+}
+
+impl<T: fmt::Debug> fmt::Debug for UserDataRefMut<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
+impl<T: fmt::Display> fmt::Display for UserDataRefMut<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
+impl<T> TryFrom<UserDataVariant<T>> for UserDataRefMut<T> {
+    type Error = Error;
+
+    #[inline]
+    fn try_from(variant: UserDataVariant<T>) -> Result<Self> {
+        let guard = variant.raw_lock().try_lock_exclusive_guarded();
+        let guard = guard.map_err(|_| Error::UserDataBorrowMutError)?;
+        let guard = unsafe { mem::transmute::<LockGuard<_>, LockGuard<'static, _>>(guard) };
+        Ok(UserDataRefMut::from_parts(
+            UserDataRefMutInner::Default(variant),
+            guard,
+        ))
+    }
+}
+
+impl<T: 'static> FromLua for UserDataRefMut<T> {
+    fn from_lua(value: Value, _: &Lua) -> Result<Self> {
+        try_value_to_userdata::<T>(value)?.borrow_mut()
+    }
+
+    unsafe fn from_stack(idx: c_int, lua: &RawLua) -> Result<Self> {
+        Self::borrow_from_stack(lua, lua.state(), idx)
+    }
+}
+
+impl<T: 'static> UserDataRefMut<T> {
+    #[inline(always)]
+    fn from_parts(inner: UserDataRefMutInner<T>, guard: LockGuard<'static, RawLock>) -> Self {
+        Self { _guard: guard, inner }
+    }
+
+    #[cfg(feature = "userdata-wrappers")]
+    fn remap<U>(
+        self,
+        f: impl FnOnce(UserDataVariant<T>) -> Result<UserDataRefMutInner<U>>,
+    ) -> Result<UserDataRefMut<U>> {
+        match &self.inner {
+            UserDataRefMutInner::Default(variant) => {
+                let inner = f(variant.clone())?;
+                Ok(UserDataRefMut::from_parts(inner, self._guard))
+            }
+            _ => Err(Error::UserDataTypeMismatch),
+        }
+    }
+
+    pub(crate) unsafe fn borrow_from_stack(
+        lua: &RawLua,
+        state: *mut ffi::lua_State,
+        idx: c_int,
+    ) -> Result<Self> {
+        let type_id = lua.get_userdata_type_id::<T>(state, idx)?;
+        match type_id {
+            Some(type_id) if type_id == TypeId::of::<T>() => {
+                let ud = get_userdata::<UserDataStorage<T>>(state, idx);
+                (*ud).try_borrow_owned_mut()
+            }
+
+            #[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+            Some(type_id) if type_id == TypeId::of::<Rc<T>>() => Err(Error::UserDataBorrowMutError),
+            #[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+            Some(type_id) if type_id == TypeId::of::<Rc<RefCell<T>>>() => {
+                let ud = get_userdata::<UserDataStorage<Rc<RefCell<T>>>>(state, idx);
+                ((*ud).try_borrow_owned_mut()).and_then(|ud| ud.transform_rc_refcell())
+            }
+
+            #[cfg(feature = "userdata-wrappers")]
+            Some(type_id) if type_id == TypeId::of::<Arc<T>>() => Err(Error::UserDataBorrowMutError),
+            #[cfg(feature = "userdata-wrappers")]
+            Some(type_id) if type_id == TypeId::of::<Arc<MutexPL<T>>>() => {
+                let ud = get_userdata::<UserDataStorage<Arc<MutexPL<T>>>>(state, idx);
+                ((*ud).try_borrow_owned_mut()).and_then(|ud| ud.transform_arc_mutex_pl())
+            }
+            #[cfg(feature = "userdata-wrappers")]
+            Some(type_id) if type_id == TypeId::of::<Arc<RwLockPL<T>>>() => {
+                let ud = get_userdata::<UserDataStorage<Arc<RwLockPL<T>>>>(state, idx);
+                ((*ud).try_borrow_owned_mut()).and_then(|ud| ud.transform_arc_rwlock_pl())
+            }
+            _ => Err(Error::UserDataTypeMismatch),
+        }
+    }
+}
+
+#[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+impl<T> UserDataRefMut<Rc<RefCell<T>>> {
+    fn transform_rc_refcell(self) -> Result<UserDataRefMut<T>> {
+        self.remap(|variant| unsafe {
+            let obj = &*variant.as_ptr();
+            let refmut = obj.try_borrow_mut().map_err(|_| Error::UserDataBorrowMutError)?;
+            let borrow = std::mem::transmute::<RefMut<T>, RefMut<'static, T>>(refmut);
+            Ok(UserDataRefMutInner::RcRefCell(borrow, variant))
+        })
+    }
+}
+
+#[cfg(feature = "userdata-wrappers")]
+impl<T> UserDataRefMut<Arc<MutexPL<T>>> {
+    fn transform_arc_mutex_pl(self) -> Result<UserDataRefMut<T>> {
+        self.remap(|variant| unsafe {
+            let obj = &*variant.as_ptr();
+            let guard = obj.try_lock().ok_or(Error::UserDataBorrowMutError)?;
+            let borrow = std::mem::transmute::<MutexGuardPL<T>, MutexGuardPL<'static, T>>(guard);
+            Ok(UserDataRefMutInner::ArcMutexPL(borrow, variant))
+        })
+    }
+}
+
+#[cfg(feature = "userdata-wrappers")]
+impl<T> UserDataRefMut<Arc<RwLockPL<T>>> {
+    fn transform_arc_rwlock_pl(self) -> Result<UserDataRefMut<T>> {
+        self.remap(|variant| unsafe {
+            let obj = &*variant.as_ptr();
+            let guard = obj.try_write().ok_or(Error::UserDataBorrowMutError)?;
+            let borrow = std::mem::transmute::<RwLockWriteGuardPL<T>, RwLockWriteGuardPL<'static, T>>(guard);
+            Ok(UserDataRefMutInner::ArcRwLockPL(borrow, variant))
+        })
+    }
+}
+
+#[allow(unused)]
+enum UserDataRefMutInner<T: 'static> {
+    Default(UserDataVariant<T>),
+
+    #[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+    RcRefCell(RefMut<'static, T>, UserDataVariant<Rc<RefCell<T>>>),
+
+    #[cfg(feature = "userdata-wrappers")]
+    ArcMutexPL(MutexGuardPL<'static, T>, UserDataVariant<Arc<MutexPL<T>>>),
+    #[cfg(feature = "userdata-wrappers")]
+    ArcRwLockPL(RwLockWriteGuardPL<'static, T>, UserDataVariant<Arc<RwLockPL<T>>>),
+}
+
+impl<T> Deref for UserDataRefMutInner<T> {
+    type Target = T;
+
+    #[inline]
+    fn deref(&self) -> &T {
+        match self {
+            Self::Default(inner) => unsafe { &*inner.as_ptr() },
+
+            #[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+            Self::RcRefCell(x, ..) => x,
+
+            #[cfg(feature = "userdata-wrappers")]
+            Self::ArcMutexPL(x, ..) => x,
+            #[cfg(feature = "userdata-wrappers")]
+            Self::ArcRwLockPL(x, ..) => x,
+        }
+    }
+}
+
+impl<T> DerefMut for UserDataRefMutInner<T> {
+    #[inline]
+    fn deref_mut(&mut self) -> &mut T {
+        match self {
+            Self::Default(inner) => unsafe { &mut *inner.as_ptr() },
+
+            #[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+            Self::RcRefCell(x, ..) => x,
+
+            #[cfg(feature = "userdata-wrappers")]
+            Self::ArcMutexPL(x, ..) => x,
+            #[cfg(feature = "userdata-wrappers")]
+            Self::ArcRwLockPL(x, ..) => x,
+        }
+    }
+}
+
+#[inline]
+fn try_value_to_userdata<T>(value: Value) -> Result<AnyUserData> {
+    match value {
+        Value::UserData(ud) => Ok(ud),
+        _ => Err(Error::FromLuaConversionError {
+            from: value.type_name(),
+            to: "userdata".to_string(),
+            message: Some(format!("expected userdata of type {}", type_name::<T>())),
+        }),
+    }
+}
+
+#[cfg(test)]
+mod assertions {
+    use super::*;
+
+    #[cfg(feature = "send")]
+    static_assertions::assert_impl_all!(UserDataRef<()>: Send, Sync);
+    #[cfg(feature = "send")]
+    static_assertions::assert_not_impl_all!(UserDataRef<std::rc::Rc<()>>: Send, Sync);
+    #[cfg(feature = "send")]
+    static_assertions::assert_impl_all!(UserDataRefMut<()>: Sync, Send);
+    #[cfg(feature = "send")]
+    static_assertions::assert_not_impl_all!(UserDataRefMut<std::rc::Rc<()>>: Send, Sync);
+
+    #[cfg(not(feature = "send"))]
+    static_assertions::assert_not_impl_all!(UserDataRef<()>: Send, Sync);
+    #[cfg(not(feature = "send"))]
+    static_assertions::assert_not_impl_all!(UserDataRefMut<()>: Send, Sync);
+}

src/userdata/registry.rs

@@ -3,35 +3,47 @@
 use std::any::TypeId;
 use std::cell::RefCell;
 use std::marker::PhantomData;
-use std::os::raw::c_int;
+use std::os::raw::c_void;
 use std::string::String as StdString;
 
 use crate::error::{Error, Result};
-use crate::state::{Lua, RawLua};
+use crate::state::{Lua, LuaGuard};
+use crate::traits::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti};
 use crate::types::{Callback, MaybeSend};
 use crate::userdata::{
-    AnyUserData, MetaMethod, UserData, UserDataFields, UserDataMethods, UserDataRef, UserDataRefMut,
+    borrow_userdata_scoped, borrow_userdata_scoped_mut, AnyUserData, MetaMethod, TypeIdHints, UserData,
+    UserDataFields, UserDataMethods, UserDataStorage,
 };
-use crate::util::{get_userdata, short_type_name};
-use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, Value};
-
-use super::cell::{UserDataBorrowMut, UserDataBorrowRef, UserDataVariant};
+use crate::util::short_type_name;
+use crate::value::Value;
 
 #[cfg(feature = "async")]
 use {
     crate::types::AsyncCallback,
+    crate::userdata::{UserDataRef, UserDataRefMut},
     std::future::{self, Future},
 };
 
-type StaticFieldCallback = Box<dyn FnOnce(&RawLua) -> Result<()> + 'static>;
+#[derive(Clone, Copy)]
+enum UserDataType {
+    Shared(TypeIdHints),
+    Unique(*mut c_void),
+}
 
 /// Handle to registry for userdata methods and metamethods.
-pub struct UserDataRegistry<T: 'static> {
+pub struct UserDataRegistry<T> {
+    lua: LuaGuard,
+    raw: RawUserDataRegistry,
+    r#type: UserDataType,
+    _phantom: PhantomData<T>,
+}
+
+pub(crate) struct RawUserDataRegistry {
     // Fields
-    pub(crate) fields: Vec<(String, StaticFieldCallback)>,
+    pub(crate) fields: Vec<(String, Result<Value>)>,
     pub(crate) field_getters: Vec<(String, Callback)>,
     pub(crate) field_setters: Vec<(String, Callback)>,
-    pub(crate) meta_fields: Vec<(String, StaticFieldCallback)>,
+    pub(crate) meta_fields: Vec<(String, Result<Value>)>,
 
     // Methods
     pub(crate) methods: Vec<(String, Callback)>,
@@ -41,12 +53,40 @@ pub struct UserDataRegistry<T: 'static> {
     #[cfg(feature = "async")]
     pub(crate) async_meta_methods: Vec<(String, AsyncCallback)>,
 
-    _type: PhantomData<T>,
+    pub(crate) destructor: ffi::lua_CFunction,
+    pub(crate) type_id: Option<TypeId>,
+    pub(crate) type_name: StdString,
 }
 
+impl UserDataType {
+    #[inline]
+    pub(crate) fn type_id(&self) -> Option<TypeId> {
+        match self {
+            UserDataType::Shared(hints) => Some(hints.type_id()),
+            UserDataType::Unique(_) => None,
+        }
+    }
+}
+
+#[cfg(feature = "send")]
+unsafe impl Send for UserDataType {}
+
 impl<T: 'static> UserDataRegistry<T> {
-    pub(crate) const fn new() -> Self {
-        UserDataRegistry {
+    #[inline(always)]
+    pub(crate) fn new(lua: &Lua) -> Self {
+        Self::with_type(lua, UserDataType::Shared(TypeIdHints::new::<T>()))
+    }
+}
+
+impl<T> UserDataRegistry<T> {
+    #[inline(always)]
+    pub(crate) fn new_unique(lua: &Lua, ud_ptr: *mut c_void) -> Self {
+        Self::with_type(lua, UserDataType::Unique(ud_ptr))
+    }
+
+    #[inline(always)]
+    fn with_type(lua: &Lua, r#type: UserDataType) -> Self {
+        let raw = RawUserDataRegistry {
             fields: Vec::new(),
             field_getters: Vec::new(),
             field_setters: Vec::new(),
@@ -57,11 +97,20 @@ impl<T: 'static> UserDataRegistry<T> {
             meta_methods: Vec::new(),
             #[cfg(feature = "async")]
             async_meta_methods: Vec::new(),
-            _type: PhantomData,
+            destructor: super::util::destroy_userdata_storage::<T>,
+            type_id: r#type.type_id(),
+            type_name: short_type_name::<T>(),
+        };
+
+        UserDataRegistry {
+            lua: lua.lock_arc(),
+            raw,
+            r#type,
+            _phantom: PhantomData,
         }
     }
 
-    fn box_method<M, A, R>(name: &str, method: M) -> Callback
+    fn box_method<M, A, R>(&self, name: &str, method: M) -> Callback
     where
         M: Fn(&Lua, &T, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti,
@@ -74,6 +123,7 @@ impl<T: 'static> UserDataRegistry<T> {
             };
         }
 
+        let target_type = self.r#type;
         Box::new(move |rawlua, nargs| unsafe {
             if nargs == 0 {
                 let err = Error::from_lua_conversion("missing argument", "userdata", None);
@@ -85,17 +135,29 @@ impl<T: 'static> UserDataRegistry<T> {
             // Self was at position 1, so we pass 2 here
             let args = A::from_stack_args(nargs - 1, 2, Some(&name), rawlua);
 
-            match try_self_arg!(rawlua.get_userdata_type_id(self_index)) {
-                Some(id) if id == TypeId::of::<T>() => {
-                    let ud = try_self_arg!(borrow_userdata_ref::<T>(state, self_index));
-                    method(rawlua.lua(), &ud, args?)?.push_into_stack_multi(rawlua)
+            match target_type {
+                #[rustfmt::skip]
+                UserDataType::Shared(type_hints) => {
+                    let type_id = try_self_arg!(rawlua.get_userdata_type_id::<T>(state, self_index));
+                    try_self_arg!(borrow_userdata_scoped(state, self_index, type_id, type_hints, |ud| {
+                        method(rawlua.lua(), ud, args?)?.push_into_stack_multi(rawlua)
+                    }))
+                }
+                UserDataType::Unique(target_ptr) if ffi::lua_touserdata(state, self_index) == target_ptr => {
+                    let ud = target_ptr as *mut UserDataStorage<T>;
+                    try_self_arg!((*ud).try_borrow_scoped(|ud| {
+                        method(rawlua.lua(), ud, args?)?.push_into_stack_multi(rawlua)
+                    }))
+                }
+                UserDataType::Unique(_) => {
+                    try_self_arg!(rawlua.get_userdata_type_id::<T>(state, self_index));
+                    Err(Error::bad_self_argument(&name, Error::UserDataTypeMismatch))
                 }
-                _ => Err(Error::bad_self_argument(&name, Error::UserDataTypeMismatch)),
             }
         })
     }
 
-    fn box_method_mut<M, A, R>(name: &str, method: M) -> Callback
+    fn box_method_mut<M, A, R>(&self, name: &str, method: M) -> Callback
     where
         M: FnMut(&Lua, &mut T, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti,
@@ -109,6 +171,7 @@ impl<T: 'static> UserDataRegistry<T> {
         }
 
         let method = RefCell::new(method);
+        let target_type = self.r#type;
         Box::new(move |rawlua, nargs| unsafe {
             let mut method = method.try_borrow_mut().map_err(|_| Error::RecursiveMutCallback)?;
             if nargs == 0 {
@@ -121,19 +184,32 @@ impl<T: 'static> UserDataRegistry<T> {
             // Self was at position 1, so we pass 2 here
             let args = A::from_stack_args(nargs - 1, 2, Some(&name), rawlua);
 
-            match try_self_arg!(rawlua.get_userdata_type_id(self_index)) {
-                Some(id) if id == TypeId::of::<T>() => {
-                    let mut ud = try_self_arg!(borrow_userdata_mut::<T>(state, self_index));
-                    method(rawlua.lua(), &mut ud, args?)?.push_into_stack_multi(rawlua)
+            match target_type {
+                #[rustfmt::skip]
+                UserDataType::Shared(type_hints) => {
+                    let type_id = try_self_arg!(rawlua.get_userdata_type_id::<T>(state, self_index));
+                    try_self_arg!(borrow_userdata_scoped_mut(state, self_index, type_id, type_hints, |ud| {
+                        method(rawlua.lua(), ud, args?)?.push_into_stack_multi(rawlua)
+                    }))
+                }
+                UserDataType::Unique(target_ptr) if ffi::lua_touserdata(state, self_index) == target_ptr => {
+                    let ud = target_ptr as *mut UserDataStorage<T>;
+                    try_self_arg!((*ud).try_borrow_scoped_mut(|ud| {
+                        method(rawlua.lua(), ud, args?)?.push_into_stack_multi(rawlua)
+                    }))
+                }
+                UserDataType::Unique(_) => {
+                    try_self_arg!(rawlua.get_userdata_type_id::<T>(state, self_index));
+                    Err(Error::bad_self_argument(&name, Error::UserDataTypeMismatch))
                 }
-                _ => Err(Error::bad_self_argument(&name, Error::UserDataTypeMismatch)),
             }
         })
     }
 
     #[cfg(feature = "async")]
-    fn box_async_method<M, A, MR, R>(name: &str, method: M) -> AsyncCallback
+    fn box_async_method<M, A, MR, R>(&self, name: &str, method: M) -> AsyncCallback
     where
+        T: 'static,
         M: Fn(Lua, UserDataRef<T>, A) -> MR + MaybeSend + 'static,
         A: FromLuaMulti,
         MR: Future<Output = Result<R>> + MaybeSend + 'static,
@@ -171,8 +247,9 @@ impl<T: 'static> UserDataRegistry<T> {
     }
 
     #[cfg(feature = "async")]
-    fn box_async_method_mut<M, A, MR, R>(name: &str, method: M) -> AsyncCallback
+    fn box_async_method_mut<M, A, MR, R>(&self, name: &str, method: M) -> AsyncCallback
     where
+        T: 'static,
         M: Fn(Lua, UserDataRefMut<T>, A) -> MR + MaybeSend + 'static,
         A: FromLuaMulti,
         MR: Future<Output = Result<R>> + MaybeSend + 'static,
@@ -209,7 +286,7 @@ impl<T: 'static> UserDataRegistry<T> {
         })
     }
 
-    fn box_function<F, A, R>(name: &str, function: F) -> Callback
+    fn box_function<F, A, R>(&self, name: &str, function: F) -> Callback
     where
         F: Fn(&Lua, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti,
@@ -222,7 +299,7 @@ impl<T: 'static> UserDataRegistry<T> {
         })
     }
 
-    fn box_function_mut<F, A, R>(name: &str, function: F) -> Callback
+    fn box_function_mut<F, A, R>(&self, name: &str, function: F) -> Callback
     where
         F: FnMut(&Lua, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti,
@@ -240,7 +317,7 @@ impl<T: 'static> UserDataRegistry<T> {
     }
 
     #[cfg(feature = "async")]
-    fn box_async_function<F, A, FR, R>(name: &str, function: F) -> AsyncCallback
+    fn box_async_function<F, A, FR, R>(&self, name: &str, function: F) -> AsyncCallback
     where
         F: Fn(Lua, A) -> FR + MaybeSend + 'static,
         A: FromLuaMulti,
@@ -275,6 +352,11 @@ impl<T: 'static> UserDataRegistry<T> {
         }
         value.into_lua(lua)
     }
+
+    #[inline(always)]
+    pub(crate) fn into_raw(self) -> RawUserDataRegistry {
+        self.raw
+    }
 }
 
 // Returns function name for the type `T`, without the module path
@@ -282,295 +364,267 @@ fn get_function_name<T>(name: &str) -> StdString {
     format!("{}.{name}", short_type_name::<T>())
 }
 
-impl<T: 'static> UserDataFields<T> for UserDataRegistry<T> {
-    fn add_field<V>(&mut self, name: impl ToString, value: V)
+impl<T> UserDataFields<T> for UserDataRegistry<T> {
+    fn add_field<V>(&mut self, name: impl Into<StdString>, value: V)
     where
         V: IntoLua + 'static,
     {
-        let name = name.to_string();
-        self.fields.push((
-            name,
-            Box::new(move |rawlua| unsafe { value.push_into_stack(rawlua) }),
-        ));
+        let name = name.into();
+        self.raw.fields.push((name, value.into_lua(self.lua.lua())));
     }
 
-    fn add_field_method_get<M, R>(&mut self, name: impl ToString, method: M)
+    fn add_field_method_get<M, R>(&mut self, name: impl Into<StdString>, method: M)
     where
         M: Fn(&Lua, &T) -> Result<R> + MaybeSend + 'static,
         R: IntoLua,
     {
-        let name = name.to_string();
-        let callback = Self::box_method(&name, move |lua, data, ()| method(lua, data));
-        self.field_getters.push((name, callback));
+        let name = name.into();
+        let callback = self.box_method(&name, move |lua, data, ()| method(lua, data));
+        self.raw.field_getters.push((name, callback));
     }
 
-    fn add_field_method_set<M, A>(&mut self, name: impl ToString, method: M)
+    fn add_field_method_set<M, A>(&mut self, name: impl Into<StdString>, method: M)
     where
         M: FnMut(&Lua, &mut T, A) -> Result<()> + MaybeSend + 'static,
         A: FromLua,
     {
-        let name = name.to_string();
-        let callback = Self::box_method_mut(&name, method);
-        self.field_setters.push((name, callback));
+        let name = name.into();
+        let callback = self.box_method_mut(&name, method);
+        self.raw.field_setters.push((name, callback));
     }
 
-    fn add_field_function_get<F, R>(&mut self, name: impl ToString, function: F)
+    fn add_field_function_get<F, R>(&mut self, name: impl Into<StdString>, function: F)
     where
         F: Fn(&Lua, AnyUserData) -> Result<R> + MaybeSend + 'static,
         R: IntoLua,
     {
-        let name = name.to_string();
-        let callback = Self::box_function(&name, function);
-        self.field_getters.push((name, callback));
+        let name = name.into();
+        let callback = self.box_function(&name, function);
+        self.raw.field_getters.push((name, callback));
     }
 
-    fn add_field_function_set<F, A>(&mut self, name: impl ToString, mut function: F)
+    fn add_field_function_set<F, A>(&mut self, name: impl Into<StdString>, mut function: F)
     where
         F: FnMut(&Lua, AnyUserData, A) -> Result<()> + MaybeSend + 'static,
         A: FromLua,
     {
-        let name = name.to_string();
-        let callback = Self::box_function_mut(&name, move |lua, (data, val)| function(lua, data, val));
-        self.field_setters.push((name, callback));
+        let name = name.into();
+        let callback = self.box_function_mut(&name, move |lua, (data, val)| function(lua, data, val));
+        self.raw.field_setters.push((name, callback));
     }
 
-    fn add_meta_field<V>(&mut self, name: impl ToString, value: V)
+    fn add_meta_field<V>(&mut self, name: impl Into<StdString>, value: V)
     where
         V: IntoLua + 'static,
     {
-        let name = name.to_string();
-        self.meta_fields.push((
-            name.clone(),
-            Box::new(move |rawlua| unsafe {
-                Self::check_meta_field(rawlua.lua(), &name, value)?.push_into_stack(rawlua)
-            }),
-        ));
+        let lua = self.lua.lua();
+        let name = name.into();
+        let field = Self::check_meta_field(lua, &name, value).and_then(|v| v.into_lua(lua));
+        self.raw.meta_fields.push((name, field));
     }
 
-    fn add_meta_field_with<F, R>(&mut self, name: impl ToString, f: F)
+    fn add_meta_field_with<F, R>(&mut self, name: impl Into<StdString>, f: F)
     where
         F: FnOnce(&Lua) -> Result<R> + 'static,
         R: IntoLua,
     {
-        let name = name.to_string();
-        self.meta_fields.push((
-            name.clone(),
-            Box::new(move |rawlua| unsafe {
-                let lua = rawlua.lua();
-                Self::check_meta_field(lua, &name, f(lua)?)?.push_into_stack(rawlua)
-            }),
-        ));
+        let lua = self.lua.lua();
+        let name = name.into();
+        let field = f(lua).and_then(|v| Self::check_meta_field(lua, &name, v).and_then(|v| v.into_lua(lua)));
+        self.raw.meta_fields.push((name, field));
     }
 }
 
-impl<T: 'static> UserDataMethods<T> for UserDataRegistry<T> {
-    fn add_method<M, A, R>(&mut self, name: impl ToString, method: M)
+impl<T> UserDataMethods<T> for UserDataRegistry<T> {
+    fn add_method<M, A, R>(&mut self, name: impl Into<StdString>, method: M)
     where
         M: Fn(&Lua, &T, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti,
         R: IntoLuaMulti,
     {
-        let name = name.to_string();
-        let callback = Self::box_method(&name, method);
-        self.methods.push((name, callback));
+        let name = name.into();
+        let callback = self.box_method(&name, method);
+        self.raw.methods.push((name, callback));
     }
 
-    fn add_method_mut<M, A, R>(&mut self, name: impl ToString, method: M)
+    fn add_method_mut<M, A, R>(&mut self, name: impl Into<StdString>, method: M)
     where
         M: FnMut(&Lua, &mut T, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti,
         R: IntoLuaMulti,
     {
-        let name = name.to_string();
-        let callback = Self::box_method_mut(&name, method);
-        self.methods.push((name, callback));
+        let name = name.into();
+        let callback = self.box_method_mut(&name, method);
+        self.raw.methods.push((name, callback));
     }
 
     #[cfg(feature = "async")]
-    fn add_async_method<M, A, MR, R>(&mut self, name: impl ToString, method: M)
+    fn add_async_method<M, A, MR, R>(&mut self, name: impl Into<StdString>, method: M)
     where
+        T: 'static,
         M: Fn(Lua, UserDataRef<T>, A) -> MR + MaybeSend + 'static,
         A: FromLuaMulti,
         MR: Future<Output = Result<R>> + MaybeSend + 'static,
         R: IntoLuaMulti,
     {
-        let name = name.to_string();
-        let callback = Self::box_async_method(&name, method);
-        self.async_methods.push((name, callback));
+        let name = name.into();
+        let callback = self.box_async_method(&name, method);
+        self.raw.async_methods.push((name, callback));
     }
 
     #[cfg(feature = "async")]
-    fn add_async_method_mut<M, A, MR, R>(&mut self, name: impl ToString, method: M)
+    fn add_async_method_mut<M, A, MR, R>(&mut self, name: impl Into<StdString>, method: M)
     where
+        T: 'static,
         M: Fn(Lua, UserDataRefMut<T>, A) -> MR + MaybeSend + 'static,
         A: FromLuaMulti,
         MR: Future<Output = Result<R>> + MaybeSend + 'static,
         R: IntoLuaMulti,
     {
-        let name = name.to_string();
-        let callback = Self::box_async_method_mut(&name, method);
-        self.async_methods.push((name, callback));
+        let name = name.into();
+        let callback = self.box_async_method_mut(&name, method);
+        self.raw.async_methods.push((name, callback));
     }
 
-    fn add_function<F, A, R>(&mut self, name: impl ToString, function: F)
+    fn add_function<F, A, R>(&mut self, name: impl Into<StdString>, function: F)
     where
         F: Fn(&Lua, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti,
         R: IntoLuaMulti,
     {
-        let name = name.to_string();
-        let callback = Self::box_function(&name, function);
-        self.methods.push((name, callback));
+        let name = name.into();
+        let callback = self.box_function(&name, function);
+        self.raw.methods.push((name, callback));
     }
 
-    fn add_function_mut<F, A, R>(&mut self, name: impl ToString, function: F)
+    fn add_function_mut<F, A, R>(&mut self, name: impl Into<StdString>, function: F)
     where
         F: FnMut(&Lua, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti,
         R: IntoLuaMulti,
     {
-        let name = name.to_string();
-        let callback = Self::box_function_mut(&name, function);
-        self.methods.push((name, callback));
+        let name = name.into();
+        let callback = self.box_function_mut(&name, function);
+        self.raw.methods.push((name, callback));
     }
 
     #[cfg(feature = "async")]
-    fn add_async_function<F, A, FR, R>(&mut self, name: impl ToString, function: F)
+    fn add_async_function<F, A, FR, R>(&mut self, name: impl Into<StdString>, function: F)
     where
         F: Fn(Lua, A) -> FR + MaybeSend + 'static,
         A: FromLuaMulti,
         FR: Future<Output = Result<R>> + MaybeSend + 'static,
         R: IntoLuaMulti,
     {
-        let name = name.to_string();
-        let callback = Self::box_async_function(&name, function);
-        self.async_methods.push((name, callback));
+        let name = name.into();
+        let callback = self.box_async_function(&name, function);
+        self.raw.async_methods.push((name, callback));
     }
 
-    fn add_meta_method<M, A, R>(&mut self, name: impl ToString, method: M)
+    fn add_meta_method<M, A, R>(&mut self, name: impl Into<StdString>, method: M)
     where
         M: Fn(&Lua, &T, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti,
         R: IntoLuaMulti,
     {
-        let name = name.to_string();
-        let callback = Self::box_method(&name, method);
-        self.meta_methods.push((name, callback));
+        let name = name.into();
+        let callback = self.box_method(&name, method);
+        self.raw.meta_methods.push((name, callback));
     }
 
-    fn add_meta_method_mut<M, A, R>(&mut self, name: impl ToString, method: M)
+    fn add_meta_method_mut<M, A, R>(&mut self, name: impl Into<StdString>, method: M)
     where
         M: FnMut(&Lua, &mut T, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti,
         R: IntoLuaMulti,
     {
-        let name = name.to_string();
-        let callback = Self::box_method_mut(&name, method);
-        self.meta_methods.push((name, callback));
+        let name = name.into();
+        let callback = self.box_method_mut(&name, method);
+        self.raw.meta_methods.push((name, callback));
     }
 
     #[cfg(all(feature = "async", not(any(feature = "lua51", feature = "luau"))))]
-    fn add_async_meta_method<M, A, MR, R>(&mut self, name: impl ToString, method: M)
+    fn add_async_meta_method<M, A, MR, R>(&mut self, name: impl Into<StdString>, method: M)
     where
+        T: 'static,
         M: Fn(Lua, UserDataRef<T>, A) -> MR + MaybeSend + 'static,
         A: FromLuaMulti,
         MR: Future<Output = Result<R>> + MaybeSend + 'static,
         R: IntoLuaMulti,
     {
-        let name = name.to_string();
-        let callback = Self::box_async_method(&name, method);
-        self.async_meta_methods.push((name, callback));
+        let name = name.into();
+        let callback = self.box_async_method(&name, method);
+        self.raw.async_meta_methods.push((name, callback));
     }
 
     #[cfg(all(feature = "async", not(any(feature = "lua51", feature = "luau"))))]
-    fn add_async_meta_method_mut<M, A, MR, R>(&mut self, name: impl ToString, method: M)
+    fn add_async_meta_method_mut<M, A, MR, R>(&mut self, name: impl Into<StdString>, method: M)
     where
+        T: 'static,
         M: Fn(Lua, UserDataRefMut<T>, A) -> MR + MaybeSend + 'static,
         A: FromLuaMulti,
         MR: Future<Output = Result<R>> + MaybeSend + 'static,
         R: IntoLuaMulti,
     {
-        let name = name.to_string();
-        let callback = Self::box_async_method_mut(&name, method);
-        self.async_meta_methods.push((name, callback));
+        let name = name.into();
+        let callback = self.box_async_method_mut(&name, method);
+        self.raw.async_meta_methods.push((name, callback));
     }
 
-    fn add_meta_function<F, A, R>(&mut self, name: impl ToString, function: F)
+    fn add_meta_function<F, A, R>(&mut self, name: impl Into<StdString>, function: F)
     where
         F: Fn(&Lua, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti,
         R: IntoLuaMulti,
     {
-        let name = name.to_string();
-        let callback = Self::box_function(&name, function);
-        self.meta_methods.push((name, callback));
+        let name = name.into();
+        let callback = self.box_function(&name, function);
+        self.raw.meta_methods.push((name, callback));
     }
 
-    fn add_meta_function_mut<F, A, R>(&mut self, name: impl ToString, function: F)
+    fn add_meta_function_mut<F, A, R>(&mut self, name: impl Into<StdString>, function: F)
     where
         F: FnMut(&Lua, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti,
         R: IntoLuaMulti,
     {
-        let name = name.to_string();
-        let callback = Self::box_function_mut(&name, function);
-        self.meta_methods.push((name, callback));
+        let name = name.into();
+        let callback = self.box_function_mut(&name, function);
+        self.raw.meta_methods.push((name, callback));
     }
 
     #[cfg(all(feature = "async", not(any(feature = "lua51", feature = "luau"))))]
-    fn add_async_meta_function<F, A, FR, R>(&mut self, name: impl ToString, function: F)
+    fn add_async_meta_function<F, A, FR, R>(&mut self, name: impl Into<StdString>, function: F)
     where
         F: Fn(Lua, A) -> FR + MaybeSend + 'static,
         A: FromLuaMulti,
         FR: Future<Output = Result<R>> + MaybeSend + 'static,
         R: IntoLuaMulti,
     {
-        let name = name.to_string();
-        let callback = Self::box_async_function(&name, function);
-        self.async_meta_methods.push((name, callback));
+        let name = name.into();
+        let callback = self.box_async_function(&name, function);
+        self.raw.async_meta_methods.push((name, callback));
     }
 }
 
-// Borrow the userdata in-place from the Lua stack
-#[inline(always)]
-unsafe fn borrow_userdata_ref<'a, T>(
-    state: *mut ffi::lua_State,
-    index: c_int,
-) -> Result<UserDataBorrowRef<'a, T>> {
-    let ud = get_userdata::<UserDataVariant<T>>(state, index);
-    (*ud).try_borrow()
-}
-
-// Borrow the userdata mutably in-place from the Lua stack
-#[inline(always)]
-unsafe fn borrow_userdata_mut<'a, T>(
-    state: *mut ffi::lua_State,
-    index: c_int,
-) -> Result<UserDataBorrowMut<'a, T>> {
-    let ud = get_userdata::<UserDataVariant<T>>(state, index);
-    (*ud).try_borrow_mut()
-}
-
 macro_rules! lua_userdata_impl {
     ($type:ty) => {
         impl<T: UserData + 'static> UserData for $type {
             fn register(registry: &mut UserDataRegistry<Self>) {
-                let mut orig_registry = UserDataRegistry::new();
+                let mut orig_registry = UserDataRegistry::new(registry.lua.lua());
                 T::register(&mut orig_registry);
 
                 // Copy all fields, methods, etc. from the original registry
-                registry.fields.extend(orig_registry.fields);
-                registry.field_getters.extend(orig_registry.field_getters);
-                registry.field_setters.extend(orig_registry.field_setters);
-                registry.meta_fields.extend(orig_registry.meta_fields);
-                registry.methods.extend(orig_registry.methods);
+                (registry.raw.fields).extend(orig_registry.raw.fields);
+                (registry.raw.field_getters).extend(orig_registry.raw.field_getters);
+                (registry.raw.field_setters).extend(orig_registry.raw.field_setters);
+                (registry.raw.meta_fields).extend(orig_registry.raw.meta_fields);
+                (registry.raw.methods).extend(orig_registry.raw.methods);
                 #[cfg(feature = "async")]
-                registry.async_methods.extend(orig_registry.async_methods);
-                registry.meta_methods.extend(orig_registry.meta_methods);
+                (registry.raw.async_methods).extend(orig_registry.raw.async_methods);
+                (registry.raw.meta_methods).extend(orig_registry.raw.meta_methods);
                 #[cfg(feature = "async")]
-                registry
-                    .async_meta_methods
-                    .extend(orig_registry.async_meta_methods);
+                (registry.raw.async_meta_methods).extend(orig_registry.raw.async_meta_methods);
             }
         }
     };
@@ -580,3 +634,24 @@ macro_rules! lua_userdata_impl {
 pub(crate) struct UserDataProxy<T>(pub(crate) PhantomData<T>);
 
 lua_userdata_impl!(UserDataProxy<T>);
+
+#[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+lua_userdata_impl!(std::rc::Rc<T>);
+#[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+lua_userdata_impl!(std::rc::Rc<std::cell::RefCell<T>>);
+#[cfg(feature = "userdata-wrappers")]
+lua_userdata_impl!(std::sync::Arc<T>);
+#[cfg(feature = "userdata-wrappers")]
+lua_userdata_impl!(std::sync::Arc<std::sync::Mutex<T>>);
+#[cfg(feature = "userdata-wrappers")]
+lua_userdata_impl!(std::sync::Arc<std::sync::RwLock<T>>);
+#[cfg(feature = "userdata-wrappers")]
+lua_userdata_impl!(std::sync::Arc<parking_lot::Mutex<T>>);
+#[cfg(feature = "userdata-wrappers")]
+lua_userdata_impl!(std::sync::Arc<parking_lot::RwLock<T>>);
+
+#[cfg(test)]
+mod assertions {
+    #[cfg(feature = "send")]
+    static_assertions::assert_impl_all!(super::RawUserDataRegistry: Send);
+}

src/userdata/util.rs

@@ -0,0 +1,469 @@
+use std::any::TypeId;
+use std::cell::Cell;
+use std::marker::PhantomData;
+use std::os::raw::c_int;
+use std::ptr;
+
+use super::UserDataStorage;
+use crate::error::{Error, Result};
+use crate::util::{get_userdata, rawget_field, rawset_field, take_userdata};
+
+// This is a trick to check if a type is `Sync` or not.
+// It uses leaked specialization feature from stdlib.
+struct IsSync<'a, T> {
+    is_sync: &'a Cell<bool>,
+    _marker: PhantomData<T>,
+}
+
+impl<T> Clone for IsSync<'_, T> {
+    fn clone(&self) -> Self {
+        self.is_sync.set(false);
+        IsSync {
+            is_sync: self.is_sync,
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl<T: Sync> Copy for IsSync<'_, T> {}
+
+pub(crate) fn is_sync<T>() -> bool {
+    let is_sync = Cell::new(true);
+    let _ = [IsSync::<T> {
+        is_sync: &is_sync,
+        _marker: PhantomData,
+    }]
+    .clone();
+    is_sync.get()
+}
+
+// Userdata type hints,  used to match types of wrapped userdata
+#[derive(Clone, Copy)]
+pub(crate) struct TypeIdHints {
+    t: TypeId,
+
+    #[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+    rc: TypeId,
+    #[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+    rc_refcell: TypeId,
+
+    #[cfg(feature = "userdata-wrappers")]
+    arc: TypeId,
+    #[cfg(feature = "userdata-wrappers")]
+    arc_mutex: TypeId,
+    #[cfg(feature = "userdata-wrappers")]
+    arc_rwlock: TypeId,
+    #[cfg(feature = "userdata-wrappers")]
+    arc_pl_mutex: TypeId,
+    #[cfg(feature = "userdata-wrappers")]
+    arc_pl_rwlock: TypeId,
+}
+
+impl TypeIdHints {
+    pub(crate) fn new<T: 'static>() -> Self {
+        Self {
+            t: TypeId::of::<T>(),
+
+            #[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+            rc: TypeId::of::<std::rc::Rc<T>>(),
+            #[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+            rc_refcell: TypeId::of::<std::rc::Rc<std::cell::RefCell<T>>>(),
+
+            #[cfg(feature = "userdata-wrappers")]
+            arc: TypeId::of::<std::sync::Arc<T>>(),
+            #[cfg(feature = "userdata-wrappers")]
+            arc_mutex: TypeId::of::<std::sync::Arc<std::sync::Mutex<T>>>(),
+            #[cfg(feature = "userdata-wrappers")]
+            arc_rwlock: TypeId::of::<std::sync::Arc<std::sync::RwLock<T>>>(),
+            #[cfg(feature = "userdata-wrappers")]
+            arc_pl_mutex: TypeId::of::<std::sync::Arc<parking_lot::Mutex<T>>>(),
+            #[cfg(feature = "userdata-wrappers")]
+            arc_pl_rwlock: TypeId::of::<std::sync::Arc<parking_lot::RwLock<T>>>(),
+        }
+    }
+
+    #[inline(always)]
+    pub(crate) fn type_id(&self) -> TypeId {
+        self.t
+    }
+}
+
+pub(crate) unsafe fn borrow_userdata_scoped<T, R>(
+    state: *mut ffi::lua_State,
+    idx: c_int,
+    type_id: Option<TypeId>,
+    type_hints: TypeIdHints,
+    f: impl FnOnce(&T) -> R,
+) -> Result<R> {
+    match type_id {
+        Some(type_id) if type_id == type_hints.t => {
+            let ud = get_userdata::<UserDataStorage<T>>(state, idx);
+            (*ud).try_borrow_scoped(|ud| f(ud))
+        }
+
+        #[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+        Some(type_id) if type_id == type_hints.rc => {
+            let ud = get_userdata::<UserDataStorage<std::rc::Rc<T>>>(state, idx);
+            (*ud).try_borrow_scoped(|ud| f(ud))
+        }
+        #[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+        Some(type_id) if type_id == type_hints.rc_refcell => {
+            let ud = get_userdata::<UserDataStorage<std::rc::Rc<std::cell::RefCell<T>>>>(state, idx);
+            (*ud).try_borrow_scoped(|ud| {
+                let ud = ud.try_borrow().map_err(|_| Error::UserDataBorrowError)?;
+                Ok(f(&ud))
+            })?
+        }
+
+        #[cfg(feature = "userdata-wrappers")]
+        Some(type_id) if type_id == type_hints.arc => {
+            let ud = get_userdata::<UserDataStorage<std::sync::Arc<T>>>(state, idx);
+            (*ud).try_borrow_scoped(|ud| f(ud))
+        }
+        #[cfg(feature = "userdata-wrappers")]
+        Some(type_id) if type_id == type_hints.arc_mutex => {
+            let ud = get_userdata::<UserDataStorage<std::sync::Arc<std::sync::Mutex<T>>>>(state, idx);
+            (*ud).try_borrow_scoped(|ud| {
+                let ud = ud.try_lock().map_err(|_| Error::UserDataBorrowError)?;
+                Ok(f(&ud))
+            })?
+        }
+        #[cfg(feature = "userdata-wrappers")]
+        Some(type_id) if type_id == type_hints.arc_rwlock => {
+            let ud = get_userdata::<UserDataStorage<std::sync::Arc<std::sync::RwLock<T>>>>(state, idx);
+            (*ud).try_borrow_scoped(|ud| {
+                let ud = ud.try_read().map_err(|_| Error::UserDataBorrowError)?;
+                Ok(f(&ud))
+            })?
+        }
+        #[cfg(feature = "userdata-wrappers")]
+        Some(type_id) if type_id == type_hints.arc_pl_mutex => {
+            let ud = get_userdata::<UserDataStorage<std::sync::Arc<parking_lot::Mutex<T>>>>(state, idx);
+            (*ud).try_borrow_scoped(|ud| {
+                let ud = ud.try_lock().ok_or(Error::UserDataBorrowError)?;
+                Ok(f(&ud))
+            })?
+        }
+        #[cfg(feature = "userdata-wrappers")]
+        Some(type_id) if type_id == type_hints.arc_pl_rwlock => {
+            let ud = get_userdata::<UserDataStorage<std::sync::Arc<parking_lot::RwLock<T>>>>(state, idx);
+            (*ud).try_borrow_scoped(|ud| {
+                let ud = ud.try_read().ok_or(Error::UserDataBorrowError)?;
+                Ok(f(&ud))
+            })?
+        }
+        _ => Err(Error::UserDataTypeMismatch),
+    }
+}
+
+pub(crate) unsafe fn borrow_userdata_scoped_mut<T, R>(
+    state: *mut ffi::lua_State,
+    idx: c_int,
+    type_id: Option<TypeId>,
+    type_hints: TypeIdHints,
+    f: impl FnOnce(&mut T) -> R,
+) -> Result<R> {
+    match type_id {
+        Some(type_id) if type_id == type_hints.t => {
+            let ud = get_userdata::<UserDataStorage<T>>(state, idx);
+            (*ud).try_borrow_scoped_mut(|ud| f(ud))
+        }
+
+        #[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+        Some(type_id) if type_id == type_hints.rc => {
+            let ud = get_userdata::<UserDataStorage<std::rc::Rc<T>>>(state, idx);
+            (*ud).try_borrow_scoped_mut(|ud| match std::rc::Rc::get_mut(ud) {
+                Some(ud) => Ok(f(ud)),
+                None => Err(Error::UserDataBorrowMutError),
+            })?
+        }
+        #[cfg(all(feature = "userdata-wrappers", not(feature = "send")))]
+        Some(type_id) if type_id == type_hints.rc_refcell => {
+            let ud = get_userdata::<UserDataStorage<std::rc::Rc<std::cell::RefCell<T>>>>(state, idx);
+            (*ud).try_borrow_scoped(|ud| {
+                let mut ud = ud.try_borrow_mut().map_err(|_| Error::UserDataBorrowMutError)?;
+                Ok(f(&mut ud))
+            })?
+        }
+
+        #[cfg(feature = "userdata-wrappers")]
+        Some(type_id) if type_id == type_hints.arc => {
+            let ud = get_userdata::<UserDataStorage<std::sync::Arc<T>>>(state, idx);
+            (*ud).try_borrow_scoped_mut(|ud| match std::sync::Arc::get_mut(ud) {
+                Some(ud) => Ok(f(ud)),
+                None => Err(Error::UserDataBorrowMutError),
+            })?
+        }
+        #[cfg(feature = "userdata-wrappers")]
+        Some(type_id) if type_id == type_hints.arc_mutex => {
+            let ud = get_userdata::<UserDataStorage<std::sync::Arc<std::sync::Mutex<T>>>>(state, idx);
+            (*ud).try_borrow_scoped_mut(|ud| {
+                let mut ud = ud.try_lock().map_err(|_| Error::UserDataBorrowMutError)?;
+                Ok(f(&mut ud))
+            })?
+        }
+        #[cfg(feature = "userdata-wrappers")]
+        Some(type_id) if type_id == type_hints.arc_rwlock => {
+            let ud = get_userdata::<UserDataStorage<std::sync::Arc<std::sync::RwLock<T>>>>(state, idx);
+            (*ud).try_borrow_scoped_mut(|ud| {
+                let mut ud = ud.try_write().map_err(|_| Error::UserDataBorrowMutError)?;
+                Ok(f(&mut ud))
+            })?
+        }
+        #[cfg(feature = "userdata-wrappers")]
+        Some(type_id) if type_id == type_hints.arc_pl_mutex => {
+            let ud = get_userdata::<UserDataStorage<std::sync::Arc<parking_lot::Mutex<T>>>>(state, idx);
+            (*ud).try_borrow_scoped_mut(|ud| {
+                let mut ud = ud.try_lock().ok_or(Error::UserDataBorrowMutError)?;
+                Ok(f(&mut ud))
+            })?
+        }
+        #[cfg(feature = "userdata-wrappers")]
+        Some(type_id) if type_id == type_hints.arc_pl_rwlock => {
+            let ud = get_userdata::<UserDataStorage<std::sync::Arc<parking_lot::RwLock<T>>>>(state, idx);
+            (*ud).try_borrow_scoped_mut(|ud| {
+                let mut ud = ud.try_write().ok_or(Error::UserDataBorrowMutError)?;
+                Ok(f(&mut ud))
+            })?
+        }
+        _ => Err(Error::UserDataTypeMismatch),
+    }
+}
+
+// Populates the given table with the appropriate members to be a userdata metatable for the given
+// type. This function takes the given table at the `metatable` index, and adds an appropriate
+// `__gc` member to it for the given type and a `__metatable` entry to protect the table from script
+// access. The function also, if given a `field_getters` or `methods` tables, will create an
+// `__index` metamethod (capturing previous one) to lookup in `field_getters` first, then `methods`
+// and falling back to the captured `__index` if no matches found.
+// The same is also applicable for `__newindex` metamethod and `field_setters` table.
+// Internally uses 9 stack spaces and does not call checkstack.
+pub(crate) unsafe fn init_userdata_metatable(
+    state: *mut ffi::lua_State,
+    metatable: c_int,
+    field_getters: Option<c_int>,
+    field_setters: Option<c_int>,
+    methods: Option<c_int>,
+) -> Result<()> {
+    if field_getters.is_some() || methods.is_some() {
+        // Push `__index` generator function
+        init_userdata_metatable_index(state)?;
+
+        let index_type = rawget_field(state, metatable, "__index")?;
+        match index_type {
+            ffi::LUA_TNIL | ffi::LUA_TTABLE | ffi::LUA_TFUNCTION => {
+                for &idx in &[field_getters, methods] {
+                    if let Some(idx) = idx {
+                        ffi::lua_pushvalue(state, idx);
+                    } else {
+                        ffi::lua_pushnil(state);
+                    }
+                }
+
+                // Generate `__index`
+                protect_lua!(state, 4, 1, fn(state) ffi::lua_call(state, 3, 1))?;
+            }
+            _ => mlua_panic!("improper `__index` type: {}", index_type),
+        }
+
+        rawset_field(state, metatable, "__index")?;
+    }
+
+    if let Some(field_setters) = field_setters {
+        // Push `__newindex` generator function
+        init_userdata_metatable_newindex(state)?;
+
+        let newindex_type = rawget_field(state, metatable, "__newindex")?;
+        match newindex_type {
+            ffi::LUA_TNIL | ffi::LUA_TTABLE | ffi::LUA_TFUNCTION => {
+                ffi::lua_pushvalue(state, field_setters);
+                // Generate `__newindex`
+                protect_lua!(state, 3, 1, fn(state) ffi::lua_call(state, 2, 1))?;
+            }
+            _ => mlua_panic!("improper `__newindex` type: {}", newindex_type),
+        }
+
+        rawset_field(state, metatable, "__newindex")?;
+    }
+
+    ffi::lua_pushboolean(state, 0);
+    rawset_field(state, metatable, "__metatable")?;
+
+    Ok(())
+}
+
+unsafe extern "C-unwind" fn lua_error_impl(state: *mut ffi::lua_State) -> c_int {
+    ffi::lua_error(state);
+}
+
+unsafe extern "C-unwind" fn lua_isfunction_impl(state: *mut ffi::lua_State) -> c_int {
+    ffi::lua_pushboolean(state, ffi::lua_isfunction(state, -1));
+    1
+}
+
+unsafe extern "C-unwind" fn lua_istable_impl(state: *mut ffi::lua_State) -> c_int {
+    ffi::lua_pushboolean(state, ffi::lua_istable(state, -1));
+    1
+}
+
+unsafe fn init_userdata_metatable_index(state: *mut ffi::lua_State) -> Result<()> {
+    let index_key = &USERDATA_METATABLE_INDEX as *const u8 as *const _;
+    if ffi::lua_rawgetp(state, ffi::LUA_REGISTRYINDEX, index_key) == ffi::LUA_TFUNCTION {
+        return Ok(());
+    }
+    ffi::lua_pop(state, 1);
+
+    // Create and cache `__index` generator
+    let code = cr#"
+        local error, isfunction, istable = ...
+        return function (__index, field_getters, methods)
+            -- Common case: has field getters and index is a table
+            if field_getters ~= nil and methods == nil and istable(__index) then
+                return function (self, key)
+                    local field_getter = field_getters[key]
+                    if field_getter ~= nil then
+                        return field_getter(self)
+                    end
+                    return __index[key]
+                end
+            end
+
+            return function (self, key)
+                if field_getters ~= nil then
+                    local field_getter = field_getters[key]
+                    if field_getter ~= nil then
+                        return field_getter(self)
+                    end
+                end
+
+                if methods ~= nil then
+                    local method = methods[key]
+                    if method ~= nil then
+                        return method
+                    end
+                end
+
+                if isfunction(__index) then
+                    return __index(self, key)
+                elseif __index == nil then
+                    error("attempt to get an unknown field '"..key.."'")
+                else
+                    return __index[key]
+                end
+            end
+        end
+    "#;
+    protect_lua!(state, 0, 1, |state| {
+        let ret = ffi::luaL_loadbuffer(state, code.as_ptr(), code.count_bytes(), cstr!("=__mlua_index"));
+        if ret != ffi::LUA_OK {
+            ffi::lua_error(state);
+        }
+        ffi::lua_pushcfunction(state, lua_error_impl);
+        ffi::lua_pushcfunction(state, lua_isfunction_impl);
+        ffi::lua_pushcfunction(state, lua_istable_impl);
+        ffi::lua_call(state, 3, 1);
+
+        #[cfg(feature = "luau-jit")]
+        if ffi::luau_codegen_supported() != 0 {
+            ffi::luau_codegen_compile(state, -1);
+        }
+
+        // Store in the registry
+        ffi::lua_pushvalue(state, -1);
+        ffi::lua_rawsetp(state, ffi::LUA_REGISTRYINDEX, index_key);
+    })
+}
+
+unsafe fn init_userdata_metatable_newindex(state: *mut ffi::lua_State) -> Result<()> {
+    let newindex_key = &USERDATA_METATABLE_NEWINDEX as *const u8 as *const _;
+    if ffi::lua_rawgetp(state, ffi::LUA_REGISTRYINDEX, newindex_key) == ffi::LUA_TFUNCTION {
+        return Ok(());
+    }
+    ffi::lua_pop(state, 1);
+
+    // Create and cache `__newindex` generator
+    let code = cr#"
+        local error, isfunction = ...
+        return function (__newindex, field_setters)
+            return function (self, key, value)
+                if field_setters ~= nil then
+                    local field_setter = field_setters[key]
+                    if field_setter ~= nil then
+                        field_setter(self, value)
+                        return
+                    end
+                end
+
+                if isfunction(__newindex) then
+                    __newindex(self, key, value)
+                elseif __newindex == nil then
+                    error("attempt to set an unknown field '"..key.."'")
+                else
+                    __newindex[key] = value
+                end
+            end
+        end
+    "#;
+    protect_lua!(state, 0, 1, |state| {
+        let code_len = code.count_bytes();
+        let ret = ffi::luaL_loadbuffer(state, code.as_ptr(), code_len, cstr!("=__mlua_newindex"));
+        if ret != ffi::LUA_OK {
+            ffi::lua_error(state);
+        }
+        ffi::lua_pushcfunction(state, lua_error_impl);
+        ffi::lua_pushcfunction(state, lua_isfunction_impl);
+        ffi::lua_call(state, 2, 1);
+
+        #[cfg(feature = "luau-jit")]
+        if ffi::luau_codegen_supported() != 0 {
+            ffi::luau_codegen_compile(state, -1);
+        }
+
+        // Store in the registry
+        ffi::lua_pushvalue(state, -1);
+        ffi::lua_rawsetp(state, ffi::LUA_REGISTRYINDEX, newindex_key);
+    })
+}
+
+// This method is called by Lua GC when it's time to collect the userdata.
+//
+// This method is usually used to collect internal userdata.
+#[cfg(not(feature = "luau"))]
+pub(crate) unsafe extern "C-unwind" fn collect_userdata<T>(state: *mut ffi::lua_State) -> c_int {
+    let ud = get_userdata::<T>(state, -1);
+    ptr::drop_in_place(ud);
+    0
+}
+
+// This method is called by Luau GC when it's time to collect the userdata.
+#[cfg(feature = "luau")]
+pub(crate) unsafe extern "C" fn collect_userdata<T>(
+    state: *mut ffi::lua_State,
+    ud: *mut std::os::raw::c_void,
+) {
+    // Almost none Lua operations are allowed when destructor is running,
+    // so we need to set a flag to prevent calling any Lua functions
+    let extra = (*ffi::lua_callbacks(state)).userdata as *mut crate::state::ExtraData;
+    (*extra).running_gc = true;
+    // Luau does not support _any_ panics in destructors (they are declared as "C", NOT as "C-unwind"),
+    // so any panics will trigger `abort()`.
+    ptr::drop_in_place(ud as *mut T);
+    (*extra).running_gc = false;
+}
+
+// This method can be called by user or Lua GC to destroy the userdata.
+// It checks if the userdata is safe to destroy and sets the "destroyed" metatable
+// to prevent further GC collection.
+pub(super) unsafe extern "C-unwind" fn destroy_userdata_storage<T>(state: *mut ffi::lua_State) -> c_int {
+    let ud = get_userdata::<UserDataStorage<T>>(state, 1);
+    if (*ud).is_safe_to_destroy() {
+        take_userdata::<UserDataStorage<T>>(state, 1);
+        ffi::lua_pushboolean(state, 1);
+    } else {
+        ffi::lua_pushboolean(state, 0);
+    }
+    1
+}
+
+static USERDATA_METATABLE_INDEX: u8 = 0;
+static USERDATA_METATABLE_NEWINDEX: u8 = 0;

src/util/error.rs

@@ -9,9 +9,8 @@ use std::sync::Arc;
 use crate::error::{Error, Result};
 use crate::memory::MemoryState;
 use crate::util::{
-    check_stack, get_internal_metatable, get_internal_userdata, init_internal_metatable,
-    push_internal_userdata, push_string, push_table, rawset_field, to_string, TypeKey,
-    DESTRUCTED_USERDATA_METATABLE,
+    check_stack, get_internal_userdata, init_internal_metatable, push_internal_userdata, push_string,
+    push_table, rawset_field, to_string, TypeKey, DESTRUCTED_USERDATA_METATABLE,
 };
 
 static WRAPPED_FAILURE_TYPE_KEY: u8 = 0;
@@ -31,12 +30,8 @@ impl TypeKey for WrappedFailure {
 
 impl WrappedFailure {
     pub(crate) unsafe fn new_userdata(state: *mut ffi::lua_State) -> *mut Self {
-        #[cfg(feature = "luau")]
-        let ud = ffi::lua_newuserdata_t::<Self>(state);
-        #[cfg(not(feature = "luau"))]
-        let ud = ffi::lua_newuserdata(state, std::mem::size_of::<Self>()) as *mut Self;
-        ptr::write(ud, WrappedFailure::None);
-        ud
+        // Unprotected calls always return `Ok`
+        push_internal_userdata(state, WrappedFailure::None, false).unwrap()
     }
 }
 
@@ -90,16 +85,11 @@ where
             let cause = Arc::new(err);
             let wrapped_error = WrappedFailure::Error(Error::CallbackError { traceback, cause });
             ptr::write(ud, wrapped_error);
-            get_internal_metatable::<WrappedFailure>(state);
-            ffi::lua_setmetatable(state, -2);
-
             ffi::lua_error(state)
         }
         Err(p) => {
             ffi::lua_settop(state, 1);
             ptr::write(ud, WrappedFailure::Panic(Some(p)));
-            get_internal_metatable::<WrappedFailure>(state);
-            ffi::lua_setmetatable(state, -2);
             ffi::lua_error(state)
         }
     }
@@ -204,24 +194,25 @@ pub(crate) unsafe fn protect_lua_closure<F, R>(
     f: F,
 ) -> Result<R>
 where
-    F: Fn(*mut ffi::lua_State) -> R,
+    F: FnOnce(*mut ffi::lua_State) -> R,
     R: Copy,
 {
     struct Params<F, R: Copy> {
-        function: F,
+        function: Option<F>,
         result: MaybeUninit<R>,
         nresults: c_int,
     }
 
     unsafe extern "C-unwind" fn do_call<F, R>(state: *mut ffi::lua_State) -> c_int
     where
-        F: Fn(*mut ffi::lua_State) -> R,
+        F: FnOnce(*mut ffi::lua_State) -> R,
         R: Copy,
     {
         let params = ffi::lua_touserdata(state, -1) as *mut Params<F, R>;
         ffi::lua_pop(state, 1);
 
-        (*params).result.write(((*params).function)(state));
+        let f = (*params).function.take().unwrap();
+        (*params).result.write(f(state));
 
         if (*params).nresults == ffi::LUA_MULTRET {
             ffi::lua_gettop(state)
@@ -241,7 +232,7 @@ where
     }
 
     let mut params = Params {
-        function: f,
+        function: Some(f),
         result: MaybeUninit::uninit(),
         nresults,
     };
@@ -261,7 +252,7 @@ where
 
 pub(crate) unsafe extern "C-unwind" fn error_traceback(state: *mut ffi::lua_State) -> c_int {
     // Luau calls error handler for memory allocation errors, skip it
-    // See https://github.com/Roblox/luau/issues/880
+    // See https://github.com/luau-lang/luau/issues/880
     #[cfg(feature = "luau")]
     if MemoryState::limit_reached(state) {
         return 0;
@@ -324,7 +315,7 @@ pub(crate) unsafe fn init_error_registry(state: *mut ffi::lua_State) -> Result<(
                     let _ = write!(&mut (*err_buf), "{error}");
                     Ok(err_buf)
                 }
-                Some(WrappedFailure::Panic(Some(ref panic))) => {
+                Some(WrappedFailure::Panic(Some(panic))) => {
                     let err_buf_key = &ERROR_PRINT_BUFFER_KEY as *const u8 as *const c_void;
                     ffi::lua_rawgetp(state, ffi::LUA_REGISTRYINDEX, err_buf_key);
                     let err_buf = ffi::lua_touserdata(state, -1) as *mut String;
@@ -358,14 +349,18 @@ pub(crate) unsafe fn init_error_registry(state: *mut ffi::lua_State) -> Result<(
         state,
         Some(|state| {
             ffi::lua_pushcfunction(state, error_tostring);
-            rawset_field(state, -2, "__tostring")
+            ffi::lua_setfield(state, -2, cstr!("__tostring"));
+
+            // This is mostly for Luau typeof() function
+            ffi::lua_pushstring(state, cstr!("error"));
+            ffi::lua_setfield(state, -2, cstr!("__type"));
         }),
     )?;
 
     // Create destructed userdata metatable
 
     unsafe extern "C-unwind" fn destructed_error(state: *mut ffi::lua_State) -> c_int {
-        callback_error(state, |_| Err(Error::CallbackDestructed))
+        callback_error(state, |_| Err(Error::UserDataDestructed))
     }
 
     push_table(state, 0, 26, true)?;

src/util/mod.rs

@@ -1,6 +1,6 @@
 use std::borrow::Cow;
 use std::ffi::CStr;
-use std::os::raw::{c_char, c_int};
+use std::os::raw::{c_char, c_int, c_void};
 use std::{ptr, slice, str};
 
 use crate::error::{Error, Result};
@@ -13,17 +13,12 @@ pub(crate) use short_names::short_type_name;
 pub(crate) use types::TypeKey;
 pub(crate) use userdata::{
     get_destructed_userdata_metatable, get_internal_metatable, get_internal_userdata, get_userdata,
-    init_internal_metatable, init_userdata_metatable, push_internal_userdata, take_userdata,
+    init_internal_metatable, push_internal_userdata, push_userdata, take_userdata,
     DESTRUCTED_USERDATA_METATABLE,
 };
 
-#[cfg(not(feature = "lua54"))]
-pub(crate) use userdata::push_userdata;
-#[cfg(feature = "lua54")]
-pub(crate) use userdata::push_userdata_uv;
-
 #[cfg(not(feature = "luau"))]
-pub(crate) use userdata::userdata_destructor;
+pub(crate) use userdata::push_uninit_userdata;
 
 // Checks that Lua has enough free stack space for future stack operations. On failure, this will
 // panic with an internal error message.
@@ -67,9 +62,15 @@ impl StackGuard {
     pub(crate) fn with_top(state: *mut ffi::lua_State, top: c_int) -> StackGuard {
         StackGuard { state, top }
     }
+
+    #[inline]
+    pub(crate) fn keep(&mut self, n: c_int) {
+        self.top += n;
+    }
 }
 
 impl Drop for StackGuard {
+    #[track_caller]
     fn drop(&mut self) {
         unsafe {
             let top = ffi::lua_gettop(self.state);
@@ -87,7 +88,7 @@ impl Drop for StackGuard {
 #[inline(always)]
 pub(crate) unsafe fn push_string(state: *mut ffi::lua_State, s: &[u8], protect: bool) -> Result<()> {
     // Always use protected mode if the string is too long
-    if protect || s.len() > (1 << 30) {
+    if protect || s.len() >= const { 1 << 30 } {
         protect_lua!(state, 0, 1, |state| {
             ffi::lua_pushlstring(state, s.as_ptr() as *const c_char, s.len());
         })
@@ -121,7 +122,7 @@ pub(crate) unsafe fn push_table(
 ) -> Result<()> {
     let narr: c_int = narr.try_into().unwrap_or(c_int::MAX);
     let nrec: c_int = nrec.try_into().unwrap_or(c_int::MAX);
-    if protect {
+    if protect || narr >= const { 1 << 30 } || nrec >= const { 1 << 27 } {
         protect_lua!(state, 0, 1, |state| ffi::lua_createtable(state, narr, nrec))
     } else {
         ffi::lua_createtable(state, narr, nrec);
@@ -129,6 +130,15 @@ pub(crate) unsafe fn push_table(
     }
 }
 
+// Uses 4 stack spaces, does not call checkstack.
+pub(crate) unsafe fn rawget_field(state: *mut ffi::lua_State, table: c_int, field: &str) -> Result<c_int> {
+    ffi::lua_pushvalue(state, table);
+    protect_lua!(state, 1, 1, |state| {
+        ffi::lua_pushlstring(state, field.as_ptr() as *const c_char, field.len());
+        ffi::lua_rawget(state, -2)
+    })
+}
+
 // Uses 4 stack spaces, does not call checkstack.
 pub(crate) unsafe fn rawset_field(state: *mut ffi::lua_State, table: c_int, field: &str) -> Result<()> {
     ffi::lua_pushvalue(state, table);
@@ -275,9 +285,25 @@ pub(crate) unsafe fn to_string(state: *mut ffi::lua_State, index: c_int) -> Stri
         ffi::LUA_TTHREAD => format!("<thread {:?}>", ffi::lua_topointer(state, index)),
         #[cfg(feature = "luau")]
         ffi::LUA_TBUFFER => format!("<buffer {:?}>", ffi::lua_topointer(state, index)),
-        #[cfg(feature = "luajit")]
-        ffi::LUA_TCDATA => format!("<cdata {:?}>", ffi::lua_topointer(state, index)),
-        _ => "<unknown>".to_string(),
+        type_id => {
+            let type_name = CStr::from_ptr(ffi::lua_typename(state, type_id)).to_string_lossy();
+            format!("<{type_name} {:?}>", ffi::lua_topointer(state, index))
+        }
+    }
+}
+
+#[inline(always)]
+pub(crate) unsafe fn get_metatable_ptr(state: *mut ffi::lua_State, index: c_int) -> *const c_void {
+    #[cfg(feature = "luau")]
+    return ffi::lua_getmetatablepointer(state, index);
+
+    #[cfg(not(feature = "luau"))]
+    if ffi::lua_getmetatable(state, index) == 0 {
+        ptr::null()
+    } else {
+        let p = ffi::lua_topointer(state, -1);
+        ffi::lua_pop(state, 1);
+        p
     }
 }
 

src/util/types.rs

@@ -10,73 +10,71 @@ pub(crate) trait TypeKey: Any {
     fn type_key() -> *const c_void;
 }
 
-static STRING_TYPE_KEY: u8 = 0;
-
 impl TypeKey for String {
     #[inline(always)]
     fn type_key() -> *const c_void {
+        static STRING_TYPE_KEY: u8 = 0;
         &STRING_TYPE_KEY as *const u8 as *const c_void
     }
 }
 
-static CALLBACK_TYPE_KEY: u8 = 0;
-
 impl TypeKey for Callback {
     #[inline(always)]
     fn type_key() -> *const c_void {
+        static CALLBACK_TYPE_KEY: u8 = 0;
         &CALLBACK_TYPE_KEY as *const u8 as *const c_void
     }
 }
 
-static CALLBACK_UPVALUE_TYPE_KEY: u8 = 0;
-
 impl TypeKey for CallbackUpvalue {
     #[inline(always)]
     fn type_key() -> *const c_void {
+        static CALLBACK_UPVALUE_TYPE_KEY: u8 = 0;
         &CALLBACK_UPVALUE_TYPE_KEY as *const u8 as *const c_void
     }
 }
 
-#[cfg(feature = "async")]
-static ASYNC_CALLBACK_TYPE_KEY: u8 = 0;
+#[cfg(not(feature = "luau"))]
+impl TypeKey for crate::types::HookCallback {
+    #[inline(always)]
+    fn type_key() -> *const c_void {
+        static HOOK_CALLBACK_TYPE_KEY: u8 = 0;
+        &HOOK_CALLBACK_TYPE_KEY as *const u8 as *const c_void
+    }
+}
 
 #[cfg(feature = "async")]
 impl TypeKey for AsyncCallback {
     #[inline(always)]
     fn type_key() -> *const c_void {
+        static ASYNC_CALLBACK_TYPE_KEY: u8 = 0;
         &ASYNC_CALLBACK_TYPE_KEY as *const u8 as *const c_void
     }
 }
 
-#[cfg(feature = "async")]
-static ASYNC_CALLBACK_UPVALUE_TYPE_KEY: u8 = 0;
-
 #[cfg(feature = "async")]
 impl TypeKey for AsyncCallbackUpvalue {
     #[inline(always)]
     fn type_key() -> *const c_void {
+        static ASYNC_CALLBACK_UPVALUE_TYPE_KEY: u8 = 0;
         &ASYNC_CALLBACK_UPVALUE_TYPE_KEY as *const u8 as *const c_void
     }
 }
 
-#[cfg(feature = "async")]
-static ASYNC_POLL_UPVALUE_TYPE_KEY: u8 = 0;
-
 #[cfg(feature = "async")]
 impl TypeKey for AsyncPollUpvalue {
     #[inline(always)]
     fn type_key() -> *const c_void {
+        static ASYNC_POLL_UPVALUE_TYPE_KEY: u8 = 0;
         &ASYNC_POLL_UPVALUE_TYPE_KEY as *const u8 as *const c_void
     }
 }
 
-#[cfg(feature = "async")]
-static WAKER_TYPE_KEY: u8 = 0;
-
 #[cfg(feature = "async")]
 impl TypeKey for Option<std::task::Waker> {
     #[inline(always)]
     fn type_key() -> *const c_void {
+        static WAKER_TYPE_KEY: u8 = 0;
         &WAKER_TYPE_KEY as *const u8 as *const c_void
     }
 }

src/util/userdata.rs

@@ -1,9 +1,9 @@
-use std::ffi::CStr;
 use std::os::raw::{c_int, c_void};
-use std::{ptr, str};
+use std::{mem, ptr};
 
 use crate::error::Result;
-use crate::util::{check_stack, push_string, push_table, rawset_field, TypeKey};
+use crate::userdata::collect_userdata;
+use crate::util::{check_stack, get_metatable_ptr, push_table, rawset_field, TypeKey};
 
 // Pushes the userdata and attaches a metatable with __gc method.
 // Internally uses 3 stack spaces, does not call checkstack.
@@ -11,11 +11,30 @@ pub(crate) unsafe fn push_internal_userdata<T: TypeKey>(
     state: *mut ffi::lua_State,
     t: T,
     protect: bool,
-) -> Result<()> {
-    push_userdata(state, t, protect)?;
+) -> Result<*mut T> {
+    #[cfg(not(feature = "luau"))]
+    let ud_ptr = if protect {
+        protect_lua!(state, 0, 1, move |state| {
+            let ud_ptr = ffi::lua_newuserdata(state, const { mem::size_of::<T>() }) as *mut T;
+            ptr::write(ud_ptr, t);
+            ud_ptr
+        })?
+    } else {
+        let ud_ptr = ffi::lua_newuserdata(state, const { mem::size_of::<T>() }) as *mut T;
+        ptr::write(ud_ptr, t);
+        ud_ptr
+    };
+
+    #[cfg(feature = "luau")]
+    let ud_ptr = if protect {
+        protect_lua!(state, 0, 1, move |state| ffi::lua_newuserdata_t::<T>(state, t))?
+    } else {
+        ffi::lua_newuserdata_t::<T>(state, t)
+    };
+
     get_internal_metatable::<T>(state);
     ffi::lua_setmetatable(state, -2);
-    Ok(())
+    Ok(ud_ptr)
 }
 
 #[track_caller]
@@ -28,7 +47,7 @@ pub(crate) unsafe fn get_internal_metatable<T: TypeKey>(state: *mut ffi::lua_Sta
 // Uses 6 stack spaces and calls checkstack.
 pub(crate) unsafe fn init_internal_metatable<T: TypeKey>(
     state: *mut ffi::lua_State,
-    customize_fn: Option<fn(*mut ffi::lua_State) -> Result<()>>,
+    customize_fn: Option<fn(*mut ffi::lua_State)>,
 ) -> Result<()> {
     check_stack(state, 6)?;
 
@@ -36,117 +55,113 @@ pub(crate) unsafe fn init_internal_metatable<T: TypeKey>(
 
     #[cfg(not(feature = "luau"))]
     {
-        ffi::lua_pushcfunction(state, userdata_destructor::<T>);
+        ffi::lua_pushcfunction(state, collect_userdata::<T>);
         rawset_field(state, -2, "__gc")?;
     }
 
     ffi::lua_pushboolean(state, 0);
     rawset_field(state, -2, "__metatable")?;
 
-    if let Some(f) = customize_fn {
-        f(state)?;
-    }
-
     protect_lua!(state, 1, 0, |state| {
+        if let Some(f) = customize_fn {
+            f(state);
+        }
+
         ffi::lua_rawsetp(state, ffi::LUA_REGISTRYINDEX, T::type_key());
     })?;
 
     Ok(())
 }
 
-// Uses 2 stack spaces, does not call checkstack
+// Uses up to 1 stack space, does not call `checkstack`
 pub(crate) unsafe fn get_internal_userdata<T: TypeKey>(
     state: *mut ffi::lua_State,
     index: c_int,
-    type_mt_ptr: *const c_void,
+    mut type_mt_ptr: *const c_void,
 ) -> *mut T {
     let ud = ffi::lua_touserdata(state, index) as *mut T;
-    if ud.is_null() || ffi::lua_getmetatable(state, index) == 0 {
+    if ud.is_null() {
         return ptr::null_mut();
     }
-    if !type_mt_ptr.is_null() {
-        let ud_mt_ptr = ffi::lua_topointer(state, -1);
-        ffi::lua_pop(state, 1);
-        if ud_mt_ptr != type_mt_ptr {
-            return ptr::null_mut();
-        }
-    } else {
+    let mt_ptr = get_metatable_ptr(state, index);
+    if type_mt_ptr.is_null() {
         get_internal_metatable::<T>(state);
-        let res = ffi::lua_rawequal(state, -1, -2);
-        ffi::lua_pop(state, 2);
-        if res == 0 {
-            return ptr::null_mut();
-        }
+        type_mt_ptr = ffi::lua_topointer(state, -1);
+        ffi::lua_pop(state, 1);
+    }
+    if mt_ptr != type_mt_ptr {
+        return ptr::null_mut();
     }
     ud
 }
 
 // Internally uses 3 stack spaces, does not call checkstack.
 #[inline]
-pub(crate) unsafe fn push_userdata<T>(state: *mut ffi::lua_State, t: T, protect: bool) -> Result<()> {
-    #[cfg(not(feature = "luau"))]
-    let ud = if protect {
+#[cfg(not(feature = "luau"))]
+pub(crate) unsafe fn push_uninit_userdata<T>(state: *mut ffi::lua_State, protect: bool) -> Result<*mut T> {
+    if protect {
         protect_lua!(state, 0, 1, |state| {
-            ffi::lua_newuserdata(state, std::mem::size_of::<T>()) as *mut T
-        })?
+            ffi::lua_newuserdata(state, const { mem::size_of::<T>() }) as *mut T
+        })
     } else {
-        ffi::lua_newuserdata(state, std::mem::size_of::<T>()) as *mut T
-    };
-    #[cfg(feature = "luau")]
-    let ud = if protect {
-        protect_lua!(state, 0, 1, |state| { ffi::lua_newuserdata_t::<T>(state) })?
-    } else {
-        ffi::lua_newuserdata_t::<T>(state)
-    };
-    ptr::write(ud, t);
-    Ok(())
+        Ok(ffi::lua_newuserdata(state, const { mem::size_of::<T>() }) as *mut T)
+    }
 }
 
 // Internally uses 3 stack spaces, does not call checkstack.
-#[cfg(feature = "lua54")]
 #[inline]
-pub(crate) unsafe fn push_userdata_uv<T>(
-    state: *mut ffi::lua_State,
-    t: T,
-    nuvalue: c_int,
-    protect: bool,
-) -> Result<()> {
-    let ud = if protect {
+pub(crate) unsafe fn push_userdata<T>(state: *mut ffi::lua_State, t: T, protect: bool) -> Result<*mut T> {
+    let size = const { mem::size_of::<T>() };
+
+    #[cfg(not(feature = "luau"))]
+    let ud_ptr = if protect {
+        protect_lua!(state, 0, 1, move |state| ffi::lua_newuserdata(state, size))?
+    } else {
+        ffi::lua_newuserdata(state, size)
+    } as *mut T;
+
+    #[cfg(feature = "luau")]
+    let ud_ptr = if protect {
         protect_lua!(state, 0, 1, |state| {
-            ffi::lua_newuserdatauv(state, std::mem::size_of::<T>(), nuvalue) as *mut T
+            ffi::lua_newuserdatadtor(state, size, collect_userdata::<T>)
         })?
     } else {
-        ffi::lua_newuserdatauv(state, std::mem::size_of::<T>(), nuvalue) as *mut T
-    };
-    ptr::write(ud, t);
-    Ok(())
+        ffi::lua_newuserdatadtor(state, size, collect_userdata::<T>)
+    } as *mut T;
+
+    ptr::write(ud_ptr, t);
+    Ok(ud_ptr)
 }
 
 #[inline]
+#[track_caller]
 pub(crate) unsafe fn get_userdata<T>(state: *mut ffi::lua_State, index: c_int) -> *mut T {
     let ud = ffi::lua_touserdata(state, index) as *mut T;
     mlua_debug_assert!(!ud.is_null(), "userdata pointer is null");
     ud
 }
 
-// Pops the userdata off of the top of the stack and returns it to rust, invalidating the lua
-// userdata and gives it the special "destructed" userdata metatable. Userdata must not have been
-// previously invalidated, and this method does not check for this.
-// Uses 1 extra stack space and does not call checkstack.
-pub(crate) unsafe fn take_userdata<T>(state: *mut ffi::lua_State) -> T {
-    // We set the metatable of userdata on __gc to a special table with no __gc method and with
-    // metamethods that trigger an error on access. We do this so that it will not be double
-    // dropped, and also so that it cannot be used or identified as any particular userdata type
-    // after the first call to __gc.
+/// Unwraps `T` from the Lua userdata and invalidating it by setting the special "destructed"
+/// metatable.
+///
+/// This method does not check that userdata is of type `T` and was not previously invalidated.
+///
+/// Uses 1 extra stack space, does not call checkstack.
+pub(crate) unsafe fn take_userdata<T>(state: *mut ffi::lua_State, idx: c_int) -> T {
+    #[rustfmt::skip]
+    let idx = if idx < 0 { ffi::lua_absindex(state, idx) } else { idx };
+
+    // Update the metatable of this userdata to a special one with no `__gc` method and with
+    // metamethods that trigger an error on access.
+    // We do this so that it will not be double dropped or used after being dropped.
     get_destructed_userdata_metatable(state);
-    ffi::lua_setmetatable(state, -2);
-    let ud = get_userdata::<T>(state, -1);
+    ffi::lua_setmetatable(state, idx);
+    let ud = get_userdata::<T>(state, idx);
 
     // Update userdata tag to disable destructor and mark as destructed
     #[cfg(feature = "luau")]
-    ffi::lua_setuserdatatag(state, -1, 1);
+    ffi::lua_setuserdatatag(state, idx, 1);
 
-    ffi::lua_pop(state, 1);
     ptr::read(ud)
 }
 
@@ -155,226 +170,4 @@ pub(crate) unsafe fn get_destructed_userdata_metatable(state: *mut ffi::lua_Stat
     ffi::lua_rawgetp(state, ffi::LUA_REGISTRYINDEX, key);
 }
 
-// Populates the given table with the appropriate members to be a userdata metatable for the given
-// type. This function takes the given table at the `metatable` index, and adds an appropriate
-// `__gc` member to it for the given type and a `__metatable` entry to protect the table from script
-// access. The function also, if given a `field_getters` or `methods` tables, will create an
-// `__index` metamethod (capturing previous one) to lookup in `field_getters` first, then `methods`
-// and falling back to the captured `__index` if no matches found.
-// The same is also applicable for `__newindex` metamethod and `field_setters` table.
-// Internally uses 9 stack spaces and does not call checkstack.
-pub(crate) unsafe fn init_userdata_metatable(
-    state: *mut ffi::lua_State,
-    metatable: c_int,
-    field_getters: Option<c_int>,
-    field_setters: Option<c_int>,
-    methods: Option<c_int>,
-    extra_init: Option<fn(*mut ffi::lua_State) -> Result<()>>,
-) -> Result<()> {
-    ffi::lua_pushvalue(state, metatable);
-
-    if field_getters.is_some() || methods.is_some() {
-        // Push `__index` generator function
-        init_userdata_metatable_index(state)?;
-
-        push_string(state, b"__index", true)?;
-        let index_type = ffi::lua_rawget(state, -3);
-        match index_type {
-            ffi::LUA_TNIL | ffi::LUA_TTABLE | ffi::LUA_TFUNCTION => {
-                for &idx in &[field_getters, methods] {
-                    if let Some(idx) = idx {
-                        ffi::lua_pushvalue(state, idx);
-                    } else {
-                        ffi::lua_pushnil(state);
-                    }
-                }
-
-                // Generate `__index`
-                protect_lua!(state, 4, 1, fn(state) ffi::lua_call(state, 3, 1))?;
-            }
-            _ => mlua_panic!("improper __index type {}", index_type),
-        }
-
-        rawset_field(state, -2, "__index")?;
-    }
-
-    if let Some(field_setters) = field_setters {
-        // Push `__newindex` generator function
-        init_userdata_metatable_newindex(state)?;
-
-        push_string(state, b"__newindex", true)?;
-        let newindex_type = ffi::lua_rawget(state, -3);
-        match newindex_type {
-            ffi::LUA_TNIL | ffi::LUA_TTABLE | ffi::LUA_TFUNCTION => {
-                ffi::lua_pushvalue(state, field_setters);
-                // Generate `__newindex`
-                protect_lua!(state, 3, 1, fn(state) ffi::lua_call(state, 2, 1))?;
-            }
-            _ => mlua_panic!("improper __newindex type {}", newindex_type),
-        }
-
-        rawset_field(state, -2, "__newindex")?;
-    }
-
-    // Additional initialization
-    if let Some(extra_init) = extra_init {
-        extra_init(state)?;
-    }
-
-    ffi::lua_pushboolean(state, 0);
-    rawset_field(state, -2, "__metatable")?;
-
-    ffi::lua_pop(state, 1);
-
-    Ok(())
-}
-
-unsafe extern "C-unwind" fn lua_error_impl(state: *mut ffi::lua_State) -> c_int {
-    ffi::lua_error(state);
-}
-
-unsafe extern "C-unwind" fn lua_isfunction_impl(state: *mut ffi::lua_State) -> c_int {
-    ffi::lua_pushboolean(state, ffi::lua_isfunction(state, -1));
-    1
-}
-
-unsafe extern "C-unwind" fn lua_istable_impl(state: *mut ffi::lua_State) -> c_int {
-    ffi::lua_pushboolean(state, ffi::lua_istable(state, -1));
-    1
-}
-
-unsafe fn init_userdata_metatable_index(state: *mut ffi::lua_State) -> Result<()> {
-    let index_key = &USERDATA_METATABLE_INDEX as *const u8 as *const _;
-    if ffi::lua_rawgetp(state, ffi::LUA_REGISTRYINDEX, index_key) == ffi::LUA_TFUNCTION {
-        return Ok(());
-    }
-    ffi::lua_pop(state, 1);
-
-    // Create and cache `__index` generator
-    let code = cstr!(
-        r#"
-            local error, isfunction, istable = ...
-            return function (__index, field_getters, methods)
-                -- Common case: has field getters and index is a table
-                if field_getters ~= nil and methods == nil and istable(__index) then
-                    return function (self, key)
-                        local field_getter = field_getters[key]
-                        if field_getter ~= nil then
-                            return field_getter(self)
-                        end
-                        return __index[key]
-                    end
-                end
-
-                return function (self, key)
-                    if field_getters ~= nil then
-                        local field_getter = field_getters[key]
-                        if field_getter ~= nil then
-                            return field_getter(self)
-                        end
-                    end
-
-                    if methods ~= nil then
-                        local method = methods[key]
-                        if method ~= nil then
-                            return method
-                        end
-                    end
-
-                    if isfunction(__index) then
-                        return __index(self, key)
-                    elseif __index == nil then
-                        error("attempt to get an unknown field '"..key.."'")
-                    else
-                        return __index[key]
-                    end
-                end
-            end
-    "#
-    );
-    let code_len = CStr::from_ptr(code).to_bytes().len();
-    protect_lua!(state, 0, 1, |state| {
-        let ret = ffi::luaL_loadbuffer(state, code, code_len, cstr!("__mlua_index"));
-        if ret != ffi::LUA_OK {
-            ffi::lua_error(state);
-        }
-        ffi::lua_pushcfunction(state, lua_error_impl);
-        ffi::lua_pushcfunction(state, lua_isfunction_impl);
-        ffi::lua_pushcfunction(state, lua_istable_impl);
-        ffi::lua_call(state, 3, 1);
-
-        #[cfg(feature = "luau-jit")]
-        if ffi::luau_codegen_supported() != 0 {
-            ffi::luau_codegen_compile(state, -1);
-        }
-
-        // Store in the registry
-        ffi::lua_pushvalue(state, -1);
-        ffi::lua_rawsetp(state, ffi::LUA_REGISTRYINDEX, index_key);
-    })
-}
-
-unsafe fn init_userdata_metatable_newindex(state: *mut ffi::lua_State) -> Result<()> {
-    let newindex_key = &USERDATA_METATABLE_NEWINDEX as *const u8 as *const _;
-    if ffi::lua_rawgetp(state, ffi::LUA_REGISTRYINDEX, newindex_key) == ffi::LUA_TFUNCTION {
-        return Ok(());
-    }
-    ffi::lua_pop(state, 1);
-
-    // Create and cache `__newindex` generator
-    let code = cstr!(
-        r#"
-            local error, isfunction = ...
-            return function (__newindex, field_setters)
-                return function (self, key, value)
-                    if field_setters ~= nil then
-                        local field_setter = field_setters[key]
-                        if field_setter ~= nil then
-                            field_setter(self, value)
-                            return
-                        end
-                    end
-
-                    if isfunction(__newindex) then
-                        __newindex(self, key, value)
-                    elseif __newindex == nil then
-                        error("attempt to set an unknown field '"..key.."'")
-                    else
-                        __newindex[key] = value
-                    end
-                end
-            end
-    "#
-    );
-    let code_len = CStr::from_ptr(code).to_bytes().len();
-    protect_lua!(state, 0, 1, |state| {
-        let ret = ffi::luaL_loadbuffer(state, code, code_len, cstr!("__mlua_newindex"));
-        if ret != ffi::LUA_OK {
-            ffi::lua_error(state);
-        }
-        ffi::lua_pushcfunction(state, lua_error_impl);
-        ffi::lua_pushcfunction(state, lua_isfunction_impl);
-        ffi::lua_call(state, 2, 1);
-
-        #[cfg(feature = "luau-jit")]
-        if ffi::luau_codegen_supported() != 0 {
-            ffi::luau_codegen_compile(state, -1);
-        }
-
-        // Store in the registry
-        ffi::lua_pushvalue(state, -1);
-        ffi::lua_rawsetp(state, ffi::LUA_REGISTRYINDEX, newindex_key);
-    })
-}
-
-#[cfg(not(feature = "luau"))]
-pub(crate) unsafe extern "C-unwind" fn userdata_destructor<T>(state: *mut ffi::lua_State) -> c_int {
-    // It's probably NOT a good idea to catch Rust panics in finalizer
-    // Lua 5.4 ignores it, other versions generates `LUA_ERRGCMM` without calling message handler
-    take_userdata::<T>(state);
-    0
-}
-
 pub(crate) static DESTRUCTED_USERDATA_METATABLE: u8 = 0;
-static USERDATA_METATABLE_INDEX: u8 = 0;
-static USERDATA_METATABLE_NEWINDEX: u8 = 0;

src/value.rs

@@ -1,35 +1,33 @@
-use std::cell::RefCell;
 use std::cmp::Ordering;
-use std::collections::{vec_deque, HashSet, VecDeque};
-use std::ops::{Deref, DerefMut};
-use std::os::raw::{c_int, c_void};
+use std::collections::HashSet;
+use std::os::raw::c_void;
 use std::string::String as StdString;
-use std::sync::Arc;
-use std::{fmt, mem, ptr, str};
+use std::{fmt, ptr, str};
 
 use num_traits::FromPrimitive;
 
 use crate::error::{Error, Result};
 use crate::function::Function;
-use crate::state::{Lua, RawLua};
 use crate::string::{BorrowedStr, String};
 use crate::table::Table;
 use crate::thread::Thread;
-use crate::types::{Integer, LightUserData, Number, SubtypeId};
+use crate::types::{Integer, LightUserData, Number, ValueRef};
 use crate::userdata::AnyUserData;
 use crate::util::{check_stack, StackGuard};
 
-#[cfg(feature = "serialize")]
+#[cfg(feature = "serde")]
 use {
     crate::table::SerializableTable,
     rustc_hash::FxHashSet,
     serde::ser::{self, Serialize, Serializer},
-    std::{rc::Rc, result::Result as StdResult},
+    std::{cell::RefCell, rc::Rc, result::Result as StdResult},
 };
 
-/// A dynamically typed Lua value. The `String`, `Table`, `Function`, `Thread`, and `UserData`
-/// variants contain handle types into the internal Lua state. It is a logic error to mix handle
-/// types between separate `Lua` instances, and doing so will result in a panic.
+/// A dynamically typed Lua value.
+///
+/// The non-primitive variants (eg. string/table/function/thread/userdata) contain handle types
+/// into the internal Lua state. It is a logic error to mix handle types between separate
+/// `Lua` instances, and doing so will result in a panic.
 #[derive(Clone)]
 pub enum Value {
     /// The Lua value `nil`.
@@ -47,7 +45,7 @@ pub enum Value {
     /// A Luau vector.
     #[cfg(any(feature = "luau", doc))]
     #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
-    Vector(crate::types::Vector),
+    Vector(crate::Vector),
     /// An interned string, managed by Lua.
     ///
     /// Unlike Rust strings, Lua strings may not be valid UTF-8.
@@ -59,10 +57,17 @@ pub enum Value {
     /// Reference to a Lua thread (or coroutine).
     Thread(Thread),
     /// Reference to a userdata object that holds a custom type which implements `UserData`.
+    ///
     /// Special builtin userdata types will be represented as other `Value` variants.
     UserData(AnyUserData),
+    /// A Luau buffer.
+    #[cfg(any(feature = "luau", doc))]
+    #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
+    Buffer(crate::Buffer),
     /// `Error` is a special builtin userdata type. When received from Lua it is implicitly cloned.
     Error(Box<Error>),
+    /// Any other value not known to mlua (eg. LuaJIT CData).
+    Other(#[doc(hidden)] ValueRef),
 }
 
 pub use self::Value::Nil;
@@ -74,7 +79,7 @@ impl Value {
     pub const NULL: Value = Value::LightUserData(LightUserData(ptr::null_mut()));
 
     /// Returns type name of this value.
-    pub const fn type_name(&self) -> &'static str {
+    pub fn type_name(&self) -> &'static str {
         match *self {
             Value::Nil => "nil",
             Value::Boolean(_) => "boolean",
@@ -87,27 +92,26 @@ impl Value {
             Value::Table(_) => "table",
             Value::Function(_) => "function",
             Value::Thread(_) => "thread",
-            Value::UserData(AnyUserData(_, SubtypeId::None)) => "userdata",
+            Value::UserData(_) => "userdata",
             #[cfg(feature = "luau")]
-            Value::UserData(AnyUserData(_, SubtypeId::Buffer)) => "buffer",
-            #[cfg(feature = "luajit")]
-            Value::UserData(AnyUserData(_, SubtypeId::CData)) => "cdata",
+            Value::Buffer(_) => "buffer",
             Value::Error(_) => "error",
+            Value::Other(_) => "other",
         }
     }
 
     /// Compares two values for equality.
     ///
     /// Equality comparisons do not convert strings to numbers or vice versa.
-    /// Tables, Functions, Threads, and Userdata are compared by reference:
+    /// Tables, functions, threads, and userdata are compared by reference:
     /// two objects are considered equal only if they are the same object.
     ///
-    /// If Tables or Userdata have `__eq` metamethod then mlua will try to invoke it.
+    /// If table or userdata have `__eq` metamethod then mlua will try to invoke it.
     /// The first value is checked first. If that value does not define a metamethod
     /// for `__eq`, then mlua will check the second value.
     /// Then mlua calls the metamethod with the two values as arguments, if found.
-    pub fn equals<T: AsRef<Self>>(&self, other: T) -> Result<bool> {
-        match (self, other.as_ref()) {
+    pub fn equals(&self, other: &Self) -> Result<bool> {
+        match (self, other) {
             (Value::Table(a), Value::Table(b)) => a.equals(b),
             (Value::UserData(a), Value::UserData(b)) => a.equals(b),
             (a, b) => Ok(a == b),
@@ -124,21 +128,42 @@ impl Value {
     #[inline]
     pub fn to_pointer(&self) -> *const c_void {
         match self {
+            Value::String(String(vref)) => {
+                // In Lua < 5.4 (excluding Luau), string pointers are NULL
+                // Use alternative approach
+                let lua = vref.lua.lock();
+                unsafe { ffi::lua_tostring(lua.ref_thread(), vref.index) as *const c_void }
+            }
             Value::LightUserData(ud) => ud.0,
-            Value::String(String(r))
-            | Value::Table(Table(r))
-            | Value::Function(Function(r))
-            | Value::Thread(Thread(r, ..))
-            | Value::UserData(AnyUserData(r, ..)) => r.to_pointer(),
+            Value::Table(Table(vref))
+            | Value::Function(Function(vref))
+            | Value::Thread(Thread(vref, ..))
+            | Value::UserData(AnyUserData(vref))
+            | Value::Other(vref) => vref.to_pointer(),
+            #[cfg(feature = "luau")]
+            Value::Buffer(crate::Buffer(vref)) => vref.to_pointer(),
             _ => ptr::null(),
         }
     }
 
     /// Converts the value to a string.
     ///
-    /// If the value has a metatable with a `__tostring` method, then it will be called to get the
-    /// result.
+    /// This might invoke the `__tostring` metamethod for non-primitive types (eg. tables,
+    /// functions).
     pub fn to_string(&self) -> Result<StdString> {
+        unsafe fn invoke_to_string(vref: &ValueRef) -> Result<StdString> {
+            let lua = vref.lua.lock();
+            let state = lua.state();
+            let _guard = StackGuard::new(state);
+            check_stack(state, 3)?;
+
+            lua.push_ref(vref);
+            protect_lua!(state, 1, 1, fn(state) {
+                ffi::luaL_tolstring(state, -1, ptr::null_mut());
+            })?;
+            Ok(String(lua.pop_ref()).to_str()?.to_string())
+        }
+
         match self {
             Value::Nil => Ok("nil".to_string()),
             Value::Boolean(b) => Ok(b.to_string()),
@@ -149,21 +174,13 @@ impl Value {
             #[cfg(feature = "luau")]
             Value::Vector(v) => Ok(v.to_string()),
             Value::String(s) => Ok(s.to_str()?.to_string()),
-            Value::Table(Table(r))
-            | Value::Function(Function(r))
-            | Value::Thread(Thread(r, ..))
-            | Value::UserData(AnyUserData(r, ..)) => unsafe {
-                let lua = r.lua.lock();
-                let state = lua.state();
-                let _guard = StackGuard::new(state);
-                check_stack(state, 3)?;
-
-                lua.push_ref(r);
-                protect_lua!(state, 1, 1, fn(state) {
-                    ffi::luaL_tolstring(state, -1, ptr::null_mut());
-                })?;
-                Ok(String(lua.pop_ref()).to_str()?.to_string())
-            },
+            Value::Table(Table(vref))
+            | Value::Function(Function(vref))
+            | Value::Thread(Thread(vref, ..))
+            | Value::UserData(AnyUserData(vref))
+            | Value::Other(vref) => unsafe { invoke_to_string(vref) },
+            #[cfg(feature = "luau")]
+            Value::Buffer(crate::Buffer(vref)) => unsafe { invoke_to_string(vref) },
             Value::Error(err) => Ok(err.to_string()),
         }
     }
@@ -175,6 +192,8 @@ impl Value {
     }
 
     /// Returns `true` if the value is a [`NULL`].
+    ///
+    /// [`NULL`]: Value::NULL
     #[inline]
     pub fn is_null(&self) -> bool {
         self == &Self::NULL
@@ -253,7 +272,10 @@ impl Value {
     /// If the value is a Lua [`Integer`], try to convert it to `i64` or return `None` otherwise.
     #[inline]
     pub fn as_i64(&self) -> Option<i64> {
-        self.as_integer().map(i64::from)
+        #[cfg(target_pointer_width = "64")]
+        return self.as_integer();
+        #[cfg(not(target_pointer_width = "64"))]
+        return self.as_integer().map(i64::from);
     }
 
     /// Cast the value to `u64`.
@@ -334,14 +356,22 @@ impl Value {
     ///
     /// If the value is a Lua [`String`], try to convert it to [`BorrowedStr`] or return `None`
     /// otherwise.
+    #[deprecated(
+        since = "0.11.0",
+        note = "This method does not follow Rust naming convention. Use `as_string().and_then(|s| s.to_str().ok())` instead."
+    )]
     #[inline]
-    pub fn as_str(&self) -> Option<BorrowedStr> {
+    pub fn as_str(&self) -> Option<BorrowedStr<'_>> {
         self.as_string().and_then(|s| s.to_str().ok())
     }
 
     /// Cast the value to [`StdString`].
     ///
     /// If the value is a Lua [`String`], converts it to [`StdString`] or returns `None` otherwise.
+    #[deprecated(
+        since = "0.11.0",
+        note = "This method does not follow Rust naming convention. Use `as_string().map(|s| s.to_string_lossy())` instead."
+    )]
     #[inline]
     pub fn as_string_lossy(&self) -> Option<StdString> {
         self.as_string().map(|s| s.to_string_lossy())
@@ -415,41 +445,60 @@ impl Value {
         }
     }
 
-    /// Returns `true` if the value is a Buffer wrapped in [`AnyUserData`].
+    /// Cast the value to a [`Buffer`].
+    ///
+    /// If the value is [`Buffer`], returns it or `None` otherwise.
+    ///
+    /// [`Buffer`]: crate::Buffer
     #[cfg(any(feature = "luau", doc))]
     #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
-    #[doc(hidden)]
     #[inline]
-    pub fn is_buffer(&self) -> bool {
-        self.as_userdata()
-            .map(|ud| ud.1 == SubtypeId::Buffer)
-            .unwrap_or_default()
+    pub fn as_buffer(&self) -> Option<&crate::Buffer> {
+        match self {
+            Value::Buffer(b) => Some(b),
+            _ => None,
+        }
     }
 
-    /// Returns `true` if the value is a CData wrapped in [`AnyUserData`].
-    #[cfg(any(feature = "luajit", doc))]
-    #[cfg_attr(docsrs, doc(cfg(feature = "luajit")))]
-    #[doc(hidden)]
+    /// Returns `true` if the value is a [`Buffer`].
+    ///
+    /// [`Buffer`]: crate::Buffer
+    #[cfg(any(feature = "luau", doc))]
+    #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
     #[inline]
-    pub fn is_cdata(&self) -> bool {
-        self.as_userdata()
-            .map(|ud| ud.1 == SubtypeId::CData)
-            .unwrap_or_default()
+    pub fn is_buffer(&self) -> bool {
+        self.as_buffer().is_some()
+    }
+
+    /// Returns `true` if the value is an [`Error`].
+    #[inline]
+    pub fn is_error(&self) -> bool {
+        self.as_error().is_some()
+    }
+
+    /// Cast the value to [`Error`].
+    ///
+    /// If the value is an [`Error`], returns it or `None` otherwise.
+    pub fn as_error(&self) -> Option<&Error> {
+        match self {
+            Value::Error(e) => Some(e),
+            _ => None,
+        }
     }
 
     /// Wrap reference to this Value into [`SerializableValue`].
     ///
     /// This allows customizing serialization behavior using serde.
-    #[cfg(feature = "serialize")]
-    #[cfg_attr(docsrs, doc(cfg(feature = "serialize")))]
+    #[cfg(feature = "serde")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
     #[doc(hidden)]
-    pub fn to_serializable(&self) -> SerializableValue {
+    pub fn to_serializable(&self) -> SerializableValue<'_> {
         SerializableValue::new(self, Default::default(), None)
     }
 
     // Compares two values.
     // Used to sort values for Debug printing.
-    pub(crate) fn cmp(&self, other: &Self) -> Ordering {
+    pub(crate) fn sort_cmp(&self, other: &Self) -> Ordering {
         fn cmp_num(a: Number, b: Number) -> Ordering {
             match (a, b) {
                 _ if a < b => Ordering::Less,
@@ -473,16 +522,19 @@ impl Value {
             (_, Value::Boolean(_)) => Ordering::Greater,
             // Integer && Number
             (Value::Integer(a), Value::Integer(b)) => a.cmp(b),
-            (&Value::Integer(a), &Value::Number(b)) => cmp_num(a as Number, b),
-            (&Value::Number(a), &Value::Integer(b)) => cmp_num(a, b as Number),
-            (&Value::Number(a), &Value::Number(b)) => cmp_num(a, b),
+            (Value::Integer(a), Value::Number(b)) => cmp_num(*a as Number, *b),
+            (Value::Number(a), Value::Integer(b)) => cmp_num(*a, *b as Number),
+            (Value::Number(a), Value::Number(b)) => cmp_num(*a, *b),
             (Value::Integer(_) | Value::Number(_), _) => Ordering::Less,
             (_, Value::Integer(_) | Value::Number(_)) => Ordering::Greater,
+            // Vector (Luau)
+            #[cfg(feature = "luau")]
+            (Value::Vector(a), Value::Vector(b)) => a.partial_cmp(b).unwrap_or(Ordering::Equal),
             // String
             (Value::String(a), Value::String(b)) => a.as_bytes().cmp(&b.as_bytes()),
             (Value::String(_), _) => Ordering::Less,
             (_, Value::String(_)) => Ordering::Greater,
-            // Other variants can be randomly ordered
+            // Other variants can be ordered by their pointer
             (a, b) => a.to_pointer().cmp(&b.to_pointer()),
         }
     }
@@ -519,17 +571,27 @@ impl Value {
                     .unwrap_or_else(|| format!("userdata: {:?}", u.to_pointer()));
                 write!(fmt, "{s}")
             }
+            #[cfg(feature = "luau")]
+            buf @ Value::Buffer(_) => write!(fmt, "buffer: {:?}", buf.to_pointer()),
             Value::Error(e) if recursive => write!(fmt, "{e:?}"),
             Value::Error(_) => write!(fmt, "error"),
+            Value::Other(v) => write!(fmt, "other: {:?}", v.to_pointer()),
         }
     }
 }
 
+impl Default for Value {
+    fn default() -> Self {
+        Self::Nil
+    }
+}
+
 impl fmt::Debug for Value {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         if fmt.alternate() {
             return self.fmt_pretty(fmt, true, 0, &mut HashSet::new());
         }
+
         match self {
             Value::Nil => write!(fmt, "Nil"),
             Value::Boolean(b) => write!(fmt, "Boolean({b})"),
@@ -543,7 +605,10 @@ impl fmt::Debug for Value {
             Value::Function(f) => write!(fmt, "{f:?}"),
             Value::Thread(t) => write!(fmt, "{t:?}"),
             Value::UserData(ud) => write!(fmt, "{ud:?}"),
+            #[cfg(feature = "luau")]
+            Value::Buffer(buf) => write!(fmt, "{buf:?}"),
             Value::Error(e) => write!(fmt, "Error({e:?})"),
+            Value::Other(v) => write!(fmt, "Other({v:?})"),
         }
     }
 }
@@ -565,21 +630,16 @@ impl PartialEq for Value {
             (Value::Function(a), Value::Function(b)) => a == b,
             (Value::Thread(a), Value::Thread(b)) => a == b,
             (Value::UserData(a), Value::UserData(b)) => a == b,
+            #[cfg(feature = "luau")]
+            (Value::Buffer(a), Value::Buffer(b)) => a == b,
             _ => false,
         }
     }
 }
 
-impl AsRef<Value> for Value {
-    #[inline]
-    fn as_ref(&self) -> &Self {
-        self
-    }
-}
-
 /// A wrapped [`Value`] with customized serialization behavior.
-#[cfg(feature = "serialize")]
-#[cfg_attr(docsrs, doc(cfg(feature = "serialize")))]
+#[cfg(feature = "serde")]
+#[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
 pub struct SerializableValue<'a> {
     value: &'a Value,
     options: crate::serde::de::Options,
@@ -587,7 +647,7 @@ pub struct SerializableValue<'a> {
     visited: Option<Rc<RefCell<FxHashSet<*const c_void>>>>,
 }
 
-#[cfg(feature = "serialize")]
+#[cfg(feature = "serde")]
 impl Serialize for Value {
     #[inline]
     fn serialize<S: Serializer>(&self, serializer: S) -> StdResult<S::Ok, S::Error> {
@@ -595,7 +655,7 @@ impl Serialize for Value {
     }
 }
 
-#[cfg(feature = "serialize")]
+#[cfg(feature = "serde")]
 impl<'a> SerializableValue<'a> {
     #[inline]
     pub(crate) fn new(
@@ -648,10 +708,19 @@ impl<'a> SerializableValue<'a> {
         self.options.sort_keys = enabled;
         self
     }
+
+    /// If true, empty Lua tables will be encoded as array, instead of map.
+    ///
+    /// Default: **false**
+    #[must_use]
+    pub const fn encode_empty_tables_as_array(mut self, enabled: bool) -> Self {
+        self.options.encode_empty_tables_as_array = enabled;
+        self
+    }
 }
 
-#[cfg(feature = "serialize")]
-impl<'a> Serialize for SerializableValue<'a> {
+#[cfg(feature = "serde")]
+impl Serialize for SerializableValue<'_> {
     fn serialize<S>(&self, serializer: S) -> StdResult<S::Ok, S::Error>
     where
         S: Serializer,
@@ -673,11 +742,14 @@ impl<'a> Serialize for SerializableValue<'a> {
             Value::UserData(ud) if ud.is_serializable() || self.options.deny_unsupported_types => {
                 ud.serialize(serializer)
             }
+            #[cfg(feature = "luau")]
+            Value::Buffer(buf) => buf.serialize(serializer),
             Value::Function(_)
             | Value::Thread(_)
             | Value::UserData(_)
             | Value::LightUserData(_)
-            | Value::Error(_) => {
+            | Value::Error(_)
+            | Value::Other(_) => {
                 if self.options.deny_unsupported_types {
                     let msg = format!("cannot serialize <{}>", self.value.type_name());
                     Err(ser::Error::custom(msg))
@@ -689,221 +761,12 @@ impl<'a> Serialize for SerializableValue<'a> {
     }
 }
 
-/// Trait for types convertible to `Value`.
-pub trait IntoLua: Sized {
-    /// Performs the conversion.
-    fn into_lua(self, lua: &Lua) -> Result<Value>;
-
-    /// Pushes the value into the Lua stack.
-    ///
-    /// # Safety
-    /// This method does not check Lua stack space.
-    #[doc(hidden)]
-    #[inline]
-    unsafe fn push_into_stack(self, lua: &RawLua) -> Result<()> {
-        lua.push_value(&self.into_lua(lua.lua())?)
-    }
-}
-
-/// Trait for types convertible from `Value`.
-pub trait FromLua: Sized {
-    /// Performs the conversion.
-    fn from_lua(value: Value, lua: &Lua) -> Result<Self>;
-
-    /// Performs the conversion for an argument (eg. function argument).
-    ///
-    /// `i` is the argument index (position),
-    /// `to` is a function name that received the argument.
-    #[doc(hidden)]
-    #[inline]
-    fn from_lua_arg(arg: Value, i: usize, to: Option<&str>, lua: &Lua) -> Result<Self> {
-        Self::from_lua(arg, lua).map_err(|err| Error::BadArgument {
-            to: to.map(|s| s.to_string()),
-            pos: i,
-            name: None,
-            cause: Arc::new(err),
-        })
-    }
-
-    /// Performs the conversion for a value in the Lua stack at index `idx`.
-    #[doc(hidden)]
-    #[inline]
-    unsafe fn from_stack(idx: c_int, lua: &RawLua) -> Result<Self> {
-        Self::from_lua(lua.stack_value(idx, None), lua.lua())
-    }
-
-    /// Same as `from_lua_arg` but for a value in the Lua stack at index `idx`.
-    #[doc(hidden)]
-    #[inline]
-    unsafe fn from_stack_arg(idx: c_int, i: usize, to: Option<&str>, lua: &RawLua) -> Result<Self> {
-        Self::from_stack(idx, lua).map_err(|err| Error::BadArgument {
-            to: to.map(|s| s.to_string()),
-            pos: i,
-            name: None,
-            cause: Arc::new(err),
-        })
-    }
-}
-
-/// Multiple Lua values used for both argument passing and also for multiple return values.
-#[derive(Default, Debug, Clone)]
-pub struct MultiValue(VecDeque<Value>);
-
-impl Deref for MultiValue {
-    type Target = VecDeque<Value>;
-
-    #[inline]
-    fn deref(&self) -> &Self::Target {
-        &self.0
-    }
-}
-
-impl DerefMut for MultiValue {
-    #[inline]
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        &mut self.0
-    }
-}
-
-impl MultiValue {
-    /// Creates an empty `MultiValue` containing no values.
-    #[inline]
-    pub const fn new() -> MultiValue {
-        MultiValue(VecDeque::new())
-    }
-
-    /// Creates an empty `MultiValue` container with space for at least `capacity` elements.
-    pub fn with_capacity(capacity: usize) -> MultiValue {
-        MultiValue(VecDeque::with_capacity(capacity))
-    }
-
-    #[inline]
-    pub(crate) fn from_lua_iter<T: IntoLua>(lua: &Lua, iter: impl IntoIterator<Item = T>) -> Result<Self> {
-        let iter = iter.into_iter();
-        let mut multi_value = MultiValue::with_capacity(iter.size_hint().0);
-        for value in iter {
-            multi_value.push_back(value.into_lua(lua)?);
-        }
-        Ok(multi_value)
-    }
-}
-
-impl FromIterator<Value> for MultiValue {
-    #[inline]
-    fn from_iter<I: IntoIterator<Item = Value>>(iter: I) -> Self {
-        let mut multi_value = MultiValue::new();
-        multi_value.extend(iter);
-        multi_value
-    }
-}
-
-impl IntoIterator for MultiValue {
-    type Item = Value;
-    type IntoIter = vec_deque::IntoIter<Value>;
-
-    #[inline]
-    fn into_iter(mut self) -> Self::IntoIter {
-        let deque = mem::take(&mut self.0);
-        mem::forget(self);
-        deque.into_iter()
-    }
-}
-
-impl<'a> IntoIterator for &'a MultiValue {
-    type Item = &'a Value;
-    type IntoIter = vec_deque::Iter<'a, Value>;
-
-    #[inline]
-    fn into_iter(self) -> Self::IntoIter {
-        self.0.iter()
-    }
-}
-
-/// Trait for types convertible to any number of Lua values.
-///
-/// This is a generalization of `IntoLua`, allowing any number of resulting Lua values instead of
-/// just one. Any type that implements `IntoLua` will automatically implement this trait.
-pub trait IntoLuaMulti: Sized {
-    /// Performs the conversion.
-    fn into_lua_multi(self, lua: &Lua) -> Result<MultiValue>;
-
-    /// Pushes the values into the Lua stack.
-    ///
-    /// Returns number of pushed values.
-    #[doc(hidden)]
-    #[inline]
-    unsafe fn push_into_stack_multi(self, lua: &RawLua) -> Result<c_int> {
-        let values = self.into_lua_multi(lua.lua())?;
-        let len: c_int = values.len().try_into().unwrap();
-        unsafe {
-            check_stack(lua.state(), len + 1)?;
-            for val in &values {
-                lua.push_value(val)?;
-            }
-        }
-        Ok(len)
-    }
-}
-
-/// Trait for types that can be created from an arbitrary number of Lua values.
-///
-/// This is a generalization of `FromLua`, allowing an arbitrary number of Lua values to participate
-/// in the conversion. Any type that implements `FromLua` will automatically implement this trait.
-pub trait FromLuaMulti: Sized {
-    /// Performs the conversion.
-    ///
-    /// In case `values` contains more values than needed to perform the conversion, the excess
-    /// values should be ignored. This reflects the semantics of Lua when calling a function or
-    /// assigning values. Similarly, if not enough values are given, conversions should assume that
-    /// any missing values are nil.
-    fn from_lua_multi(values: MultiValue, lua: &Lua) -> Result<Self>;
-
-    /// Performs the conversion for a list of arguments.
-    ///
-    /// `i` is an index (position) of the first argument,
-    /// `to` is a function name that received the arguments.
-    #[doc(hidden)]
-    #[inline]
-    fn from_lua_args(args: MultiValue, i: usize, to: Option<&str>, lua: &Lua) -> Result<Self> {
-        let _ = (i, to);
-        Self::from_lua_multi(args, lua)
-    }
-
-    /// Performs the conversion for a number of values in the Lua stack.
-    #[doc(hidden)]
-    #[inline]
-    unsafe fn from_stack_multi(nvals: c_int, lua: &RawLua) -> Result<Self> {
-        let mut values = MultiValue::with_capacity(nvals as usize);
-        for idx in 0..nvals {
-            values.push_back(lua.stack_value(-nvals + idx, None));
-        }
-        if nvals > 0 {
-            // It's safe to clear the stack as all references moved to ref thread
-            ffi::lua_pop(lua.state(), nvals);
-        }
-        Self::from_lua_multi(values, lua.lua())
-    }
-
-    /// Same as `from_lua_args` but for a number of values in the Lua stack.
-    #[doc(hidden)]
-    #[inline]
-    unsafe fn from_stack_args(nargs: c_int, i: usize, to: Option<&str>, lua: &RawLua) -> Result<Self> {
-        let _ = (i, to);
-        Self::from_stack_multi(nargs, lua)
-    }
-}
-
 #[cfg(test)]
 mod assertions {
     use super::*;
 
     #[cfg(not(feature = "send"))]
     static_assertions::assert_not_impl_any!(Value: Send);
-    #[cfg(not(feature = "send"))]
-    static_assertions::assert_not_impl_any!(MultiValue: Send);
-
     #[cfg(feature = "send")]
     static_assertions::assert_impl_all!(Value: Send, Sync);
-    #[cfg(feature = "send")]
-    static_assertions::assert_impl_all!(MultiValue: Send, Sync);
 }

src/vector.rs

@@ -1,6 +1,6 @@
 use std::fmt;
 
-#[cfg(all(any(feature = "luau", doc), feature = "serialize"))]
+#[cfg(feature = "serde")]
 use serde::ser::{Serialize, SerializeTupleStruct, Serializer};
 
 /// A Luau vector type.
@@ -8,7 +8,7 @@ use serde::ser::{Serialize, SerializeTupleStruct, Serializer};
 /// By default vectors are 3-dimensional, but can be 4-dimensional
 /// if the `luau-vector4` feature is enabled.
 #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
-#[derive(Debug, Default, Clone, Copy, PartialEq)]
+#[derive(Debug, Default, Clone, Copy, PartialEq, PartialOrd)]
 pub struct Vector(pub(crate) [f32; Self::SIZE]);
 
 impl fmt::Display for Vector {
@@ -21,6 +21,7 @@ impl fmt::Display for Vector {
     }
 }
 
+#[cfg_attr(not(feature = "luau"), allow(unused))]
 impl Vector {
     pub(crate) const SIZE: usize = if cfg!(feature = "luau-vector4") { 4 } else { 3 };
 
@@ -37,7 +38,6 @@ impl Vector {
     }
 
     /// Creates a new vector with all components set to `0.0`.
-    #[doc(hidden)]
     pub const fn zero() -> Self {
         Self([0.0; Self::SIZE])
     }
@@ -65,7 +65,7 @@ impl Vector {
     }
 }
 
-#[cfg(all(any(feature = "luau", doc), feature = "serialize"))]
+#[cfg(feature = "serde")]
 impl Serialize for Vector {
     fn serialize<S: Serializer>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error> {
         let mut ts = serializer.serialize_tuple_struct("Vector", Self::SIZE)?;
@@ -84,3 +84,8 @@ impl PartialEq<[f32; Self::SIZE]> for Vector {
         self.0 == *other
     }
 }
+
+#[cfg(feature = "luau")]
+impl crate::types::LuaType for Vector {
+    const TYPE_ID: std::os::raw::c_int = ffi::LUA_TVECTOR;
+}

tarpaulin.toml

@@ -1,8 +1,23 @@
-[lua54_coverage]
-features = "lua54,vendored,async,serialize,macros"
+[lua54]
+features = "lua54,vendored,async,send,serde,macros,anyhow,userdata-wrappers"
 
-[lua51_coverage]
-features = "lua51,vendored,async,serialize,macros"
+[lua54_non_send]
+features = "lua54,vendored,async,serde,macros,anyhow,userdata-wrappers"
 
-[luau_coverage]
-features = "luau,async,serialize,macros"
+[lua54_with_memory_limit]
+features = "lua54,vendored,async,send,serde,macros,anyhow,userdata-wrappers"
+rustflags = "--cfg force_memory_limit"
+
+[lua51]
+features = "lua51,vendored,async,send,serde,macros"
+
+[lua51_with_memory_limit]
+features = "lua51,vendored,async,send,serde,macros"
+rustflags = "--cfg force_memory_limit"
+
+[luau]
+features = "luau,async,send,serde,macros"
+
+[luau_with_memory_limit]
+features = "luau,async,send,serde,macros"
+rustflags = "--cfg force_memory_limit"

tests/async.rs

@@ -1,5 +1,6 @@
 #![cfg(feature = "async")]
 
+use std::string::String as StdString;
 use std::sync::Arc;
 use std::time::Duration;
 
@@ -8,7 +9,7 @@ use tokio::sync::Mutex;
 
 use mlua::{
     Error, Function, Lua, LuaOptions, MultiValue, ObjectLike, Result, StdLib, Table, UserData,
-    UserDataMethods, Value,
+    UserDataMethods, UserDataRef, Value,
 };
 
 #[cfg(not(target_arch = "wasm32"))]
@@ -39,12 +40,51 @@ async fn test_async_function() -> Result<()> {
 async fn test_async_function_wrap() -> Result<()> {
     let lua = Lua::new();
 
-    let f = Function::wrap_async(|_, s: String| async move { Ok(s) });
+    let f = Function::wrap_async(|s: StdString| async move {
+        tokio::task::yield_now().await;
+        Ok(s)
+    });
     lua.globals().set("f", f)?;
-
     let res: String = lua.load(r#"f("hello")"#).eval_async().await?;
     assert_eq!(res, "hello");
 
+    // Return error
+    let ferr = Function::wrap_async(|| async move { Err::<(), _>(Error::runtime("some async error")) });
+    lua.globals().set("ferr", ferr)?;
+    lua.load(
+        r#"
+        local ok, err = pcall(ferr)
+        assert(not ok and tostring(err):find("some async error"))
+    "#,
+    )
+    .exec_async()
+    .await
+    .unwrap();
+
+    Ok(())
+}
+
+#[tokio::test]
+async fn test_async_function_wrap_raw() -> Result<()> {
+    let lua = Lua::new();
+
+    let f = Function::wrap_raw_async(|s: StdString| async move {
+        tokio::task::yield_now().await;
+        s
+    });
+    lua.globals().set("f", f)?;
+    let res: String = lua.load(r#"f("hello")"#).eval_async().await?;
+    assert_eq!(res, "hello");
+
+    // Return error
+    let ferr = Function::wrap_raw_async(|| async move {
+        tokio::task::yield_now().await;
+        Err::<(), _>("some error")
+    });
+    lua.globals().set("ferr", ferr)?;
+    let (_, err): (Value, String) = lua.load(r#"ferr()"#).eval_async().await?;
+    assert_eq!(err, "some error");
+
     Ok(())
 }
 
@@ -233,7 +273,7 @@ async fn test_async_lua54_to_be_closed() -> Result<()> {
 
     // Don't close by default when awaiting async threads
     let co = lua.create_thread(f.clone())?;
-    let _ = co.clone().into_async::<()>(()).await;
+    let _ = co.clone().into_async::<()>(())?.await;
     assert_eq!(globals.get::<usize>("close_count")?, 1);
     let _ = co.reset(f);
     assert_eq!(globals.get::<usize>("close_count")?, 2);
@@ -260,7 +300,7 @@ async fn test_async_thread_stream() -> Result<()> {
         .eval()?,
     )?;
 
-    let mut stream = thread.into_async::<i64>(1);
+    let mut stream = thread.into_async::<i64>(1)?;
     let mut sum = 0;
     while let Some(n) = stream.try_next().await? {
         sum += n;
@@ -285,7 +325,7 @@ async fn test_async_thread() -> Result<()> {
         }
     })?;
 
-    let res: String = lua.create_thread(f)?.into_async(()).await?;
+    let res: String = lua.create_thread(f)?.into_async(())?.await?;
 
     assert_eq!(res, "done");
 
@@ -346,9 +386,16 @@ async fn test_async_table_object_like() -> Result<()> {
             table.get::<i64>("val")
         })?,
     )?;
-    table.set_metatable(Some(metatable));
+    table.set_metatable(Some(metatable))?;
     assert_eq!(table.call_async::<i64>(()).await.unwrap(), 15);
 
+    match table.call_async_method::<()>("non_existent", ()).await {
+        Err(Error::RuntimeError(err)) => {
+            assert!(err.contains("attempt to call a nil value (function 'non_existent')"))
+        }
+        r => panic!("expected RuntimeError, got {r:?}"),
+    }
+
     Ok(())
 }
 
@@ -500,6 +547,7 @@ async fn test_async_thread_error() -> Result<()> {
 
 #[tokio::test]
 async fn test_async_terminate() -> Result<()> {
+    // Future captures `Lua` instance and dropped all together
     let mutex = Arc::new(Mutex::new(0u32));
     {
         let lua = Lua::new();
@@ -518,5 +566,104 @@ async fn test_async_terminate() -> Result<()> {
     }
     assert!(mutex.try_lock().is_ok());
 
+    // Future is dropped, but `Lua` instance is still alive
+    let lua = Lua::new();
+    let func = lua.create_async_function(move |_, mutex: UserDataRef<Arc<Mutex<u32>>>| async move {
+        let _guard = mutex.lock().await;
+        sleep_ms(100).await;
+        Ok(())
+    })?;
+    let mutex2 = lua.create_any_userdata(mutex.clone())?;
+    let _ = tokio::time::timeout(Duration::from_millis(30), func.call_async::<()>(mutex2)).await;
+    assert!(mutex.try_lock().is_ok());
+
+    Ok(())
+}
+
+#[tokio::test]
+async fn test_async_task() -> Result<()> {
+    let lua = Lua::new();
+
+    let delay = lua.create_function(|lua, (secs, f, args): (f32, Function, MultiValue)| {
+        let thread = lua.create_thread(f)?;
+        let thread2 = thread.clone().into_async::<()>(args)?;
+        tokio::task::spawn_local(async move {
+            tokio::time::sleep(Duration::from_secs_f32(secs)).await;
+            _ = thread2.await;
+        });
+        Ok(thread)
+    })?;
+
+    lua.globals().set("delay", delay)?;
+    let local = tokio::task::LocalSet::new();
+    local
+        .run_until(async {
+            _ = lua
+                .load("delay(0.1, function(msg) global_msg = msg end, 'done')")
+                .exec_async()
+                .await;
+        })
+        .await;
+    local.await;
+    assert_eq!(lua.globals().get::<String>("global_msg")?, "done");
+
+    Ok(())
+}
+
+#[tokio::test]
+async fn test_async_task_abort() -> Result<()> {
+    let lua = Lua::new();
+
+    let sleep = lua.create_async_function(move |_lua, n: u64| async move {
+        sleep_ms(n).await;
+        Ok(())
+    })?;
+    lua.globals().set("sleep", sleep)?;
+
+    let local = tokio::task::LocalSet::new();
+    local
+        .run_until(async {
+            let lua2 = lua.clone();
+            let jh = tokio::task::spawn_local(async move {
+                lua2.load("sleep(200) result = 'done'")
+                    .exec_async()
+                    .await
+                    .unwrap();
+            });
+            sleep_ms(100).await; // Wait for the task to start
+            jh.abort();
+        })
+        .await;
+    local.await;
+    assert_eq!(lua.globals().get::<Value>("result")?, Value::Nil);
+
+    Ok(())
+}
+
+#[tokio::test]
+#[cfg(not(feature = "luau"))]
+async fn test_async_hook() -> Result<()> {
+    use std::sync::atomic::{AtomicBool, Ordering};
+
+    let lua = Lua::new();
+
+    static HOOK_CALLED: AtomicBool = AtomicBool::new(false);
+    lua.set_global_hook(mlua::HookTriggers::new().every_line(), move |_, _| {
+        if !HOOK_CALLED.swap(true, Ordering::Relaxed) {
+            #[cfg(any(feature = "lu53", feature = "lua54"))]
+            return Ok(mlua::VmState::Yield);
+        }
+        Ok(mlua::VmState::Continue)
+    })?;
+
+    let sleep = lua.create_async_function(move |_lua, n: u64| async move {
+        sleep_ms(n).await;
+        Ok(())
+    })?;
+    lua.globals().set("sleep", sleep)?;
+
+    lua.load(r"sleep(100)").exec_async().await?;
+    assert!(HOOK_CALLED.load(Ordering::Relaxed));
+
     Ok(())
 }

tests/buffer.rs

@@ -0,0 +1,57 @@
+#![cfg(feature = "luau")]
+
+use mlua::{Lua, Result, Value};
+
+#[test]
+fn test_buffer() -> Result<()> {
+    let lua = Lua::new();
+
+    let buf1 = lua
+        .load(
+            r#"
+        local buf = buffer.fromstring("hello")
+        assert(buffer.len(buf) == 5)
+        return buf
+    "#,
+        )
+        .eval::<Value>()?;
+    assert!(buf1.is_buffer());
+    assert_eq!(buf1.type_name(), "buffer");
+
+    let buf2 = lua.load("buffer.fromstring('hello')").eval::<Value>()?;
+    assert_ne!(buf1, buf2);
+
+    // Check that we can pass buffer type to Lua
+    let buf1 = buf1.as_buffer().unwrap();
+    let func = lua.create_function(|_, buf: Value| return buf.to_string())?;
+    assert!(func.call::<String>(buf1)?.starts_with("buffer:"));
+
+    // Check buffer methods
+    assert_eq!(buf1.len(), 5);
+    assert_eq!(buf1.to_vec(), b"hello");
+    assert_eq!(buf1.read_bytes::<3>(1), [b'e', b'l', b'l']);
+    buf1.write_bytes(1, b"i");
+    assert_eq!(buf1.to_vec(), b"hillo");
+
+    let buf3 = lua.create_buffer(b"")?;
+    assert!(buf3.is_empty());
+    assert!(!Value::Buffer(buf3).to_pointer().is_null());
+
+    Ok(())
+}
+
+#[test]
+#[should_panic(expected = "range end index 14 out of range for slice of length 13")]
+fn test_buffer_out_of_bounds_read() {
+    let lua = Lua::new();
+    let buf = lua.create_buffer(b"hello, world!").unwrap();
+    _ = buf.read_bytes::<1>(13);
+}
+
+#[test]
+#[should_panic(expected = "range end index 16 out of range for slice of length 13")]
+fn test_buffer_out_of_bounds_write() {
+    let lua = Lua::new();
+    let buf = lua.create_buffer(b"hello, world!").unwrap();
+    buf.write_bytes(14, b"!!");
+}

tests/chunk.rs

@@ -1,6 +1,24 @@
 use std::{fs, io};
 
-use mlua::{Lua, Result};
+use mlua::{Chunk, ChunkMode, Lua, Result};
+
+#[test]
+fn test_chunk_methods() -> Result<()> {
+    let lua = Lua::new();
+
+    #[cfg(unix)]
+    assert!(lua.load("return 123").name().starts_with("@tests/chunk.rs"));
+    let chunk2 = lua.load("return 123").set_name("@new_name");
+    assert_eq!(chunk2.name(), "@new_name");
+
+    let env = lua.create_table_from([("a", 987)])?;
+    let chunk3 = lua.load("return a").set_environment(env.clone());
+    assert_eq!(chunk3.environment().unwrap(), &env);
+    assert_eq!(chunk3.mode(), ChunkMode::Text);
+    assert_eq!(chunk3.call::<i32>(())?, 987);
+
+    Ok(())
+}
 
 #[test]
 fn test_chunk_path() -> Result<()> {
@@ -19,7 +37,7 @@ fn test_chunk_path() -> Result<()> {
         return 321
     "#,
     )?;
-    let i: i32 = lua.load(&*temp_dir.path().join("module.lua")).eval()?;
+    let i: i32 = lua.load(temp_dir.path().join("module.lua")).eval()?;
     assert_eq!(i, 321);
 
     match lua.load(&*temp_dir.path().join("module2.lua")).exec() {
@@ -27,6 +45,30 @@ fn test_chunk_path() -> Result<()> {
         res => panic!("expected io::Error, got {:?}", res),
     };
 
+    // &Path
+    assert_eq!(
+        (lua.load(&*temp_dir.path().join("module.lua").as_path())).eval::<i32>()?,
+        321
+    );
+
+    Ok(())
+}
+
+#[test]
+fn test_chunk_impls() -> Result<()> {
+    let lua = Lua::new();
+
+    // StdString
+    assert_eq!(lua.load(String::from("1")).eval::<i32>()?, 1);
+    assert_eq!(lua.load(&String::from("2")).eval::<i32>()?, 2);
+
+    // &[u8]
+    assert_eq!(lua.load(&b"3"[..]).eval::<i32>()?, 3);
+
+    // Vec<u8>
+    assert_eq!(lua.load(b"4".to_vec()).eval::<i32>()?, 4);
+    assert_eq!(lua.load(&b"5".to_vec()).eval::<i32>()?, 5);
+
     Ok(())
 }
 
@@ -42,7 +84,7 @@ fn test_chunk_macro() -> Result<()> {
     data.raw_set("num", 1)?;
 
     let ud = mlua::AnyUserData::wrap("hello");
-    let f = mlua::Function::wrap(|_lua, ()| Ok(()));
+    let f = mlua::Function::wrap(|| Ok(()));
 
     lua.globals().set("g", 123)?;
 
@@ -68,3 +110,71 @@ fn test_chunk_macro() -> Result<()> {
 
     Ok(())
 }
+
+#[cfg(feature = "luau")]
+#[test]
+fn test_compiler() -> Result<()> {
+    let compiler = mlua::Compiler::new()
+        .set_optimization_level(2)
+        .set_debug_level(2)
+        .set_type_info_level(1)
+        .set_coverage_level(2)
+        .set_vector_ctor("vector.new")
+        .set_vector_type("vector")
+        .set_mutable_globals(["mutable_global"])
+        .set_userdata_types(["MyUserdata"])
+        .set_disabled_builtins(["tostring"]);
+
+    assert!(compiler.compile("return tostring(vector.new(1, 2, 3))").is_ok());
+
+    // Error
+    match compiler.compile("%") {
+        Err(mlua::Error::SyntaxError { ref message, .. }) => {
+            assert!(message.contains("Expected identifier when parsing expression, got '%'"),);
+        }
+        res => panic!("expected result: {res:?}"),
+    }
+
+    Ok(())
+}
+
+#[cfg(feature = "luau")]
+#[test]
+fn test_compiler_library_constants() {
+    use mlua::{Compiler, Vector};
+
+    let compiler = Compiler::new()
+        .set_optimization_level(2)
+        .add_library_constant("mylib.const_bool", true)
+        .add_library_constant("mylib.const_num", 123.0)
+        .add_library_constant("mylib.const_vec", Vector::zero())
+        .add_library_constant("mylib.const_str", "value1");
+
+    let lua = Lua::new();
+    lua.set_compiler(compiler);
+    let const_bool = lua.load("return mylib.const_bool").eval::<bool>().unwrap();
+    assert_eq!(const_bool, true);
+    let const_num = lua.load("return mylib.const_num").eval::<f64>().unwrap();
+    assert_eq!(const_num, 123.0);
+    let const_vec = lua.load("return mylib.const_vec").eval::<Vector>().unwrap();
+    assert_eq!(const_vec, Vector::zero());
+    let const_str = lua.load("return mylib.const_str").eval::<String>();
+    assert_eq!(const_str.unwrap(), "value1");
+}
+
+#[test]
+fn test_chunk_wrap() -> Result<()> {
+    let lua = Lua::new();
+
+    let f = Chunk::wrap("return 123");
+    lua.globals().set("f", f)?;
+    lua.load("assert(f() == 123)").exec().unwrap();
+
+    lua.globals().set("f2", Chunk::wrap("c()"))?;
+    assert!(
+        (lua.load("f2()").exec().err().unwrap().to_string()).contains(file!()),
+        "wrong chunk location"
+    );
+
+    Ok(())
+}

tests/compile.rs

@@ -7,8 +7,6 @@ fn test_compilation() {
     t.compile_fail("tests/compile/lua_norefunwindsafe.rs");
     t.compile_fail("tests/compile/ref_nounwindsafe.rs");
     t.compile_fail("tests/compile/scope_callback_capture.rs");
-    t.compile_fail("tests/compile/scope_callback_inner.rs");
-    t.compile_fail("tests/compile/scope_callback_outer.rs");
     t.compile_fail("tests/compile/scope_invariance.rs");
     t.compile_fail("tests/compile/scope_mutable_aliasing.rs");
     t.compile_fail("tests/compile/scope_userdata_borrow.rs");
@@ -17,7 +15,6 @@ fn test_compilation() {
     {
         t.compile_fail("tests/compile/async_any_userdata_method.rs");
         t.compile_fail("tests/compile/async_nonstatic_userdata.rs");
-        t.compile_fail("tests/compile/async_userdata_method.rs");
     }
 
     #[cfg(feature = "send")]

tests/compile/async_any_userdata_method.rs

@@ -1,4 +1,4 @@
-use mlua::{UserDataMethods, Lua};
+use mlua::{Lua, UserDataMethods};
 
 fn main() {
     let lua = Lua::new();
@@ -6,9 +6,10 @@ fn main() {
     lua.register_userdata_type::<String>(|reg| {
         let s = String::new();
         let mut s = &s;
-        reg.add_async_method("t", |_, this: &String, ()| async {
-            s = this;
+        reg.add_async_method("t", |_, this, ()| async {
+            s = &*this;
             Ok(())
         });
-    }).unwrap();
+    })
+    .unwrap();
 }

tests/compile/async_any_userdata_method.stderr

@@ -1,20 +1,42 @@
 error[E0596]: cannot borrow `s` as mutable, as it is a captured variable in a `Fn` closure
-  --> tests/compile/async_any_userdata_method.rs:9:58
+  --> tests/compile/async_any_userdata_method.rs:9:49
    |
-9  |         reg.add_async_method("t", |_, this: &String, ()| async {
-   |                                                          ^^^^^ cannot borrow as mutable
-10 |             s = this;
+9  |         reg.add_async_method("t", |_, this, ()| async {
+   |                                                 ^^^^^ cannot borrow as mutable
+10 |             s = &*this;
    |             - mutable borrow occurs due to use of `s` in closure
 
-error: lifetime may not live long enough
-  --> tests/compile/async_any_userdata_method.rs:9:58
+error[E0373]: async block may outlive the current function, but it borrows `this`, which is owned by the current function
+  --> tests/compile/async_any_userdata_method.rs:9:49
    |
-9  |           reg.add_async_method("t", |_, this: &String, ()| async {
-   |  ___________________________________----------------------_^
-   | |                                   |                    |
-   | |                                   |                    return type of closure `{async block@$DIR/tests/compile/async_any_userdata_method.rs:9:58: 9:63}` contains a lifetime `'2`
+9  |         reg.add_async_method("t", |_, this, ()| async {
+   |                                                 ^^^^^ may outlive borrowed value `this`
+10 |             s = &*this;
+   |                   ---- `this` is borrowed here
+   |
+note: async block is returned here
+  --> tests/compile/async_any_userdata_method.rs:9:49
+   |
+9  |           reg.add_async_method("t", |_, this, ()| async {
+   |  _________________________________________________^
+10 | |             s = &*this;
+11 | |             Ok(())
+12 | |         });
+   | |_________^
+help: to force the async block to take ownership of `this` (and any other referenced variables), use the `move` keyword
+   |
+9  |         reg.add_async_method("t", |_, this, ()| async move {
+   |                                                       ++++
+
+error: lifetime may not live long enough
+  --> tests/compile/async_any_userdata_method.rs:9:49
+   |
+9  |           reg.add_async_method("t", |_, this, ()| async {
+   |  ___________________________________-------------_^
+   | |                                   |           |
+   | |                                   |           return type of closure `{async block@$DIR/tests/compile/async_any_userdata_method.rs:9:49: 9:54}` contains a lifetime `'2`
    | |                                   lifetime `'1` represents this closure's body
-10 | |             s = this;
+10 | |             s = &*this;
 11 | |             Ok(())
 12 | |         });
    | |_________^ returning this value requires that `'1` must outlive `'2`
@@ -28,53 +50,31 @@ error[E0597]: `s` does not live long enough
    |               - binding `s` declared here
 8  |           let mut s = &s;
    |                       ^^ borrowed value does not live long enough
-9  | /         reg.add_async_method("t", |_, this: &String, ()| async {
-10 | |             s = this;
+9  | /         reg.add_async_method("t", |_, this, ()| async {
+10 | |             s = &*this;
 11 | |             Ok(())
 12 | |         });
    | |__________- argument requires that `s` is borrowed for `'static`
-13 |       }).unwrap();
+13 |       })
    |       - `s` dropped here while still borrowed
 
-error[E0521]: borrowed data escapes outside of closure
-  --> tests/compile/async_any_userdata_method.rs:9:9
-   |
-6  |       lua.register_userdata_type::<String>(|reg| {
-   |                                             ---
-   |                                             |
-   |                                             `reg` is a reference that is only valid in the closure body
-   |                                             has type `&mut LuaUserDataRegistry<'1, std::string::String>`
-...
-9  | /         reg.add_async_method("t", |_, this: &String, ()| async {
-10 | |             s = this;
-11 | |             Ok(())
-12 | |         });
-   | |          ^
-   | |          |
-   | |__________`reg` escapes the closure body here
-   |            argument requires that `'1` must outlive `'static`
-   |
-   = note: requirement occurs because of a mutable reference to `LuaUserDataRegistry<'_, std::string::String>`
-   = note: mutable references are invariant over their type parameter
-   = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
-
 error[E0373]: closure may outlive the current function, but it borrows `s`, which is owned by the current function
   --> tests/compile/async_any_userdata_method.rs:9:35
    |
-9  |         reg.add_async_method("t", |_, this: &String, ()| async {
-   |                                   ^^^^^^^^^^^^^^^^^^^^^^ may outlive borrowed value `s`
-10 |             s = this;
+9  |         reg.add_async_method("t", |_, this, ()| async {
+   |                                   ^^^^^^^^^^^^^ may outlive borrowed value `s`
+10 |             s = &*this;
    |             - `s` is borrowed here
    |
 note: function requires argument type to outlive `'static`
   --> tests/compile/async_any_userdata_method.rs:9:9
    |
-9  | /         reg.add_async_method("t", |_, this: &String, ()| async {
-10 | |             s = this;
+9  | /         reg.add_async_method("t", |_, this, ()| async {
+10 | |             s = &*this;
 11 | |             Ok(())
 12 | |         });
    | |__________^
 help: to force the closure to take ownership of `s` (and any other referenced variables), use the `move` keyword
    |
-9  |         reg.add_async_method("t", move |_, this: &String, ()| async {
+9  |         reg.add_async_method("t", move |_, this, ()| async {
    |                                   ++++

tests/compile/async_nonstatic_userdata.rs

@@ -4,8 +4,8 @@ fn main() {
     #[derive(Clone)]
     struct MyUserData<'a>(&'a i64);
 
-    impl<'a> UserData for MyUserData<'a> {
-        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+    impl UserData for MyUserData<'_> {
+        fn add_methods<M: UserDataMethods<Self>>(methods: &mut M) {
             methods.add_async_method("print", |_, data, ()| async move {
                 println!("{}", data.0);
                 Ok(())

tests/compile/async_nonstatic_userdata.stderr

@@ -1,11 +1,11 @@
 error: lifetime may not live long enough
   --> tests/compile/async_nonstatic_userdata.rs:9:13
    |
-7  |       impl<'a> UserData for MyUserData<'a> {
-   |            -- lifetime `'a` defined here
-8  |           fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+7  |       impl UserData for MyUserData<'_> {
+   |                                    -- lifetime `'1` appears in the `impl`'s self type
+8  |           fn add_methods<M: UserDataMethods<Self>>(methods: &mut M) {
 9  | /             methods.add_async_method("print", |_, data, ()| async move {
 10 | |                 println!("{}", data.0);
 11 | |                 Ok(())
 12 | |             });
-   | |______________^ requires that `'a` must outlive `'static`
+   | |______________^ requires that `'1` must outlive `'static`

tests/compile/async_userdata_method.rs

@@ -1,14 +0,0 @@
-use mlua::{UserData, UserDataMethods};
-
-struct MyUserData;
-
-impl UserData for MyUserData {
-    fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
-        methods.add_async_method("method", |_, this: &'static Self, ()| async {
-            Ok(())
-        });
-        // ^ lifetime may not live long enough
-    }
-}
-
-fn main() {}

tests/compile/async_userdata_method.stderr

@@ -1,17 +0,0 @@
-warning: unused variable: `this`
- --> tests/compile/async_userdata_method.rs:7:48
-  |
-7 |         methods.add_async_method("method", |_, this: &'static Self, ()| async {
-  |                                                ^^^^ help: if this is intentional, prefix it with an underscore: `_this`
-  |
-  = note: `#[warn(unused_variables)]` on by default
-
-error: lifetime may not live long enough
- --> tests/compile/async_userdata_method.rs:7:9
-  |
-6 |       fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
-  |                      ---- lifetime `'lua` defined here
-7 | /         methods.add_async_method("method", |_, this: &'static Self, ()| async {
-8 | |             Ok(())
-9 | |         });
-  | |__________^ argument requires that `'lua` must outlive `'static`

tests/compile/function_borrow.rs

@@ -6,7 +6,5 @@ fn main() {
     let test = Test(0);
 
     let lua = Lua::new();
-    let _ = lua.create_function(|_, ()| -> Result<i32> {
-        Ok(test.0)
-    });
+    let _ = lua.create_function(|_, ()| -> Result<i32> { Ok(test.0) });
 }

tests/compile/function_borrow.stderr

@@ -1,20 +1,17 @@
 error[E0373]: closure may outlive the current function, but it borrows `test.0`, which is owned by the current function
-  --> tests/compile/function_borrow.rs:9:33
-   |
-9  |     let _ = lua.create_function(|_, ()| -> Result<i32> {
-   |                                 ^^^^^^^^^^^^^^^^^^^^^^ may outlive borrowed value `test.0`
-10 |         Ok(test.0)
-   |            ------ `test.0` is borrowed here
-   |
+ --> tests/compile/function_borrow.rs:9:33
+  |
+9 |     let _ = lua.create_function(|_, ()| -> Result<i32> { Ok(test.0) });
+  |                                 ^^^^^^^^^^^^^^^^^^^^^^      ------ `test.0` is borrowed here
+  |                                 |
+  |                                 may outlive borrowed value `test.0`
+  |
 note: function requires argument type to outlive `'static`
-  --> tests/compile/function_borrow.rs:9:13
-   |
-9  |       let _ = lua.create_function(|_, ()| -> Result<i32> {
-   |  _____________^
-10 | |         Ok(test.0)
-11 | |     });
-   | |______^
+ --> tests/compile/function_borrow.rs:9:13
+  |
+9 |     let _ = lua.create_function(|_, ()| -> Result<i32> { Ok(test.0) });
+  |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 help: to force the closure to take ownership of `test.0` (and any other referenced variables), use the `move` keyword
-   |
-9  |     let _ = lua.create_function(move |_, ()| -> Result<i32> {
-   |                                 ++++
+  |
+9 |     let _ = lua.create_function(move |_, ()| -> Result<i32> { Ok(test.0) });
+  |                                 ++++

tests/compile/lua_norefunwindsafe.stderr

@@ -6,7 +6,7 @@ error[E0277]: the type `UnsafeCell<*mut lua_State>` may contain interior mutabil
   |     |
   |     required by a bound introduced by this call
   |
-  = help: within `mlua::types::sync::inner::ReentrantMutex<mlua::state::raw::RawLua>`, the trait `RefUnwindSafe` is not implemented for `UnsafeCell<*mut lua_State>`, which is required by `{closure@$DIR/tests/compile/lua_norefunwindsafe.rs:7:18: 7:20}: UnwindSafe`
+  = help: within `mlua::types::sync::inner::ReentrantMutex<mlua::state::raw::RawLua>`, the trait `RefUnwindSafe` is not implemented for `UnsafeCell<*mut lua_State>`
 note: required because it appears within the type `Cell<*mut lua_State>`
  --> $RUST/core/src/cell.rs
   |
@@ -26,7 +26,7 @@ note: required because it appears within the type `mlua::types::sync::inner::Ree
 note: required because it appears within the type `Lua`
  --> src/state.rs
   |
-  | pub struct Lua(XRc<ReentrantMutex<RawLua>>);
+  | pub struct Lua {
   |            ^^^
   = note: required for `&Lua` to implement `UnwindSafe`
 note: required because it's used within this closure
@@ -48,7 +48,7 @@ error[E0277]: the type `UnsafeCell<mlua::state::extra::ExtraData>` may contain i
   |     |
   |     required by a bound introduced by this call
   |
-  = help: the trait `RefUnwindSafe` is not implemented for `UnsafeCell<mlua::state::extra::ExtraData>`, which is required by `{closure@$DIR/tests/compile/lua_norefunwindsafe.rs:7:18: 7:20}: UnwindSafe`
+  = help: the trait `RefUnwindSafe` is not implemented for `UnsafeCell<mlua::state::extra::ExtraData>`
   = note: required for `Rc<UnsafeCell<mlua::state::extra::ExtraData>>` to implement `RefUnwindSafe`
 note: required because it appears within the type `mlua::state::raw::RawLua`
  --> src/state/raw.rs
@@ -64,7 +64,7 @@ note: required because it appears within the type `mlua::types::sync::inner::Ree
 note: required because it appears within the type `Lua`
  --> src/state.rs
   |
-  | pub struct Lua(XRc<ReentrantMutex<RawLua>>);
+  | pub struct Lua {
   |            ^^^
   = note: required for `&Lua` to implement `UnwindSafe`
 note: required because it's used within this closure

tests/compile/non_send.rs

@@ -8,10 +8,8 @@ fn main() -> Result<()> {
 
     let data = Rc::new(Cell::new(0));
 
-    lua.create_function(move |_, ()| {
-        Ok(data.get())
-    })?
-    .call::<i32>(())?;
+    lua.create_function(move |_, ()| Ok(data.get()))?
+        .call::<i32>(())?;
 
     Ok(())
 }

tests/compile/non_send.stderr

@@ -1,28 +1,25 @@
 error[E0277]: `Rc<Cell<i32>>` cannot be sent between threads safely
   --> tests/compile/non_send.rs:11:25
    |
-11 |       lua.create_function(move |_, ()| {
-   |           --------------- ^-----------
-   |           |               |
-   |  _________|_______________within this `{closure@$DIR/tests/compile/non_send.rs:11:25: 11:37}`
-   | |         |
-   | |         required by a bound introduced by this call
-12 | |         Ok(data.get())
-13 | |     })?
-   | |_____^ `Rc<Cell<i32>>` cannot be sent between threads safely
+11 |     lua.create_function(move |_, ()| Ok(data.get()))?
+   |         --------------- ------------^^^^^^^^^^^^^^^
+   |         |               |
+   |         |               `Rc<Cell<i32>>` cannot be sent between threads safely
+   |         |               within this `{closure@$DIR/tests/compile/non_send.rs:11:25: 11:37}`
+   |         required by a bound introduced by this call
    |
    = help: within `{closure@$DIR/tests/compile/non_send.rs:11:25: 11:37}`, the trait `Send` is not implemented for `Rc<Cell<i32>>`
 note: required because it's used within this closure
   --> tests/compile/non_send.rs:11:25
    |
-11 |     lua.create_function(move |_, ()| {
+11 |     lua.create_function(move |_, ()| Ok(data.get()))?
    |                         ^^^^^^^^^^^^
-   = note: required for `{closure@$DIR/tests/compile/non_send.rs:11:25: 11:37}` to implement `mlua::types::MaybeSend`
+   = note: required for `{closure@$DIR/tests/compile/non_send.rs:11:25: 11:37}` to implement `MaybeSend`
 note: required by a bound in `Lua::create_function`
-  --> src/lua.rs
+  --> src/state.rs
    |
-   |     pub fn create_function<'lua, A, R, F>(&'lua self, func: F) -> Result<Function<'lua>>
+   |     pub fn create_function<F, A, R>(&self, func: F) -> Result<Function>
    |            --------------- required by a bound in this associated function
-...
-   |         F: Fn(&'lua Lua, A) -> Result<R> + MaybeSend + 'static,
-   |                                            ^^^^^^^^^ required by this bound in `Lua::create_function`
+   |     where
+   |         F: Fn(&Lua, A) -> Result<R> + MaybeSend + 'static,
+   |                                       ^^^^^^^^^ required by this bound in `Lua::create_function`