v0.10.0-beta.2

They are immutable and don't require holding a lock

.github/workflows/main.yml

@@ -27,7 +27,8 @@ jobs:
       - name: Build ${{ matrix.lua }} vendored
         run: |
           cargo build --features "${{ matrix.lua }},vendored"
-          cargo build --features "${{ matrix.lua }},vendored,async,send,serialize,macros,parking_lot,unstable"
+          cargo build --features "${{ matrix.lua }},vendored,async,serialize,macros"
+          cargo build --features "${{ matrix.lua }},vendored,async,serialize,macros,send"
         shell: bash
       - name: Build ${{ matrix.lua }} pkg-config
         if: ${{ matrix.os == 'ubuntu-22.04' }}
@@ -50,7 +51,7 @@ jobs:
           toolchain: stable
           target: aarch64-apple-darwin
       - name: Cross-compile
-        run: cargo build --target aarch64-apple-darwin --features "${{ matrix.lua }},vendored,async,send,serialize,macros,parking_lot,unstable"
+        run: cargo build --target aarch64-apple-darwin --features "${{ matrix.lua }},vendored,async,send,serialize,macros"
 
   build_aarch64_cross_ubuntu:
     name: Cross-compile to aarch64-unknown-linux-gnu
@@ -71,7 +72,7 @@ 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 "${{ matrix.lua }},vendored,async,send,serialize,macros,parking_lot,unstable"
+        run: cargo build --target aarch64-unknown-linux-gnu --features "${{ matrix.lua }},vendored,async,send,serialize,macros"
         shell: bash
 
   build_armv7_cross_ubuntu:
@@ -93,7 +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 "${{ matrix.lua }},vendored,async,send,serialize,macros,parking_lot,unstable"
+        run: cargo build --target armv7-unknown-linux-gnueabihf --features "${{ matrix.lua }},vendored,async,send,serialize,macros"
         shell: bash
 
   test:
@@ -122,14 +123,14 @@ jobs:
       - name: Run ${{ matrix.lua }} tests
         run: |
           cargo test --features "${{ matrix.lua }},vendored"
-          cargo test --features "${{ matrix.lua }},vendored,async,send,serialize,macros,parking_lot"
-          cargo test --features "${{ matrix.lua }},vendored,async,serialize,macros,parking_lot,unstable"
+          cargo test --features "${{ matrix.lua }},vendored,async,serialize,macros"
+          cargo test --features "${{ matrix.lua }},vendored,async,serialize,macros,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 "${{ matrix.lua }},vendored,async,send,serialize,macros,parking_lot,unstable" -- --ignored
+          TRYBUILD=overwrite cargo test --features "${{ matrix.lua }},vendored,async,send,serialize,macros" -- --ignored
         shell: bash
 
   test_with_sanitizer:
@@ -153,7 +154,8 @@ jobs:
       - uses: Swatinem/rust-cache@v2
       - name: Run ${{ matrix.lua }} tests with address sanitizer
         run: |
-            cargo test --tests --features "${{ matrix.lua }},vendored,async,send,serialize,macros,parking_lot,unstable" --target x86_64-unknown-linux-gnu -- --skip test_too_many_recursions
+          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
         shell: bash
         env:
           RUSTFLAGS: -Z sanitizer=address
@@ -226,17 +228,15 @@ jobs:
       - name: Run ${{ matrix.lua }} tests
         run: |
           cargo test --tests --features "${{ matrix.lua }},vendored"
-          cargo test --tests --features "${{ matrix.lua }},vendored,async,send,serialize,macros,parking_lot"
-          cargo test --tests --features "${{ matrix.lua }},vendored,async,serialize,macros,parking_lot,unstable"
+          cargo test --tests --features "${{ matrix.lua }},vendored,async,serialize,macros"
 
   rustfmt:
     name: Rustfmt
     runs-on: ubuntu-22.04
     steps:
       - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@stable
+      - uses: dtolnay/rust-toolchain@nightly
         with:
-          toolchain: stable
           components: rustfmt
       - run: cargo fmt -- --check
 
@@ -255,4 +255,4 @@ jobs:
       - uses: giraffate/clippy-action@v1
         with:
           reporter: 'github-pr-review'
-          clippy_flags: --features "${{ matrix.lua }},vendored,async,send,serialize,macros,parking_lot,unstable"
+          clippy_flags: --features "${{ matrix.lua }},vendored,async,send,serialize,macros"

CHANGELOG.md

@@ -1,3 +1,72 @@
+## v0.10.0-beta.2
+
+- Updated `ThreadStatus` enum to include `Running` and `Finished` variants.
+- `Error::CoroutineInactive` renamed to `Error::CoroutineUnresumable`.
+- `IntoLua`/`IntoLuaMulti` now uses `impl trait` syntax for args (shorten from `a.get::<_, T>` to `a.get::<T>`).
+- Removed undocumented `Lua::into_static`/`from_static` methods.
+- Futures now require `Send` bound if `send` feature is enabled.
+- Dropped lifetime from `UserDataMethods` and `UserDataFields` traits.
+- `Compiler::compile()` now returns `Result` (Luau).
+- Removed `Clone` requirement from `UserDataFields::add_field()`.
+- `TableExt` and `AnyUserDataExt` traits were combined into `ObjectLike` trait.
+- Disabled `send` feature in module mode (since we don't have exclusive access to Lua).
+- `Chunk::set_environment()` takes `Table` instead of `IntoLua` type.
+- Reduced the compile time contribution of `next_key_seed` and `next_value_seed`.
+- Reduced the compile time contribution of `serde_userdata`.
+- Performance improvements.
+
+## v0.10.0-beta.1
+
+- Dropped `'lua` lifetime (subtypes now store a weak reference to Lua)
+- Removed (experimental) owned types (they no longer needed)
+- Make Lua types truly `Send` and `Sync` (when enabling `send` feature flag)
+- Removed `UserData` impl for Rc/Arc types ("any" userdata functions can be used instead)
+- `Lua::replace_registry_value` takes `&mut RegistryKey`
+- `Lua::scope` temporary disabled (will be re-added in the next release)
+
+## v0.9.9
+
+- Minimal Luau updated to 0.629
+- Fixed bug when attempting to reset or resume already running coroutines (#416).
+- Added `RegistryKey::id()` method to get the underlying Lua registry key id.
+
+## v0.9.8
+
+- Fixed serializing same table multiple times (#408)
+- Use `mlua-sys` v0.6 (to support Luau 0.624+)
+- Fixed cross compilation of windows dlls from unix (#394)
+
+## v0.9.7
+
+- Implemented `IntoLua` for `RegistryKey`
+- Mark `__idiv` metamethod as available for luau
+- Added `Function::deep_clone()` method (Luau)
+- Added `SerializeOptions::detect_serde_json_arbitrary_precision` option
+- Added `Lua::create_buffer()` method (Luau)
+- Support serializing buffer type as a byte slice (Luau)
+- Perf: Implemented `push_into_stack`/`from_stack` for `Option<T>`
+- Added `Lua::create_ser_any_userdata()` method
+
+## v0.9.6
+
+- Added `to_pointer` function to `Function`/`Table`/`Thread`
+- Implemented `IntoLua` for `&Value`
+- Implemented `FromLua` for `RegistryKey`
+- Faster (~5%) table array traversal during serialization
+- Some performance improvements for bool/int types
+
+## v0.9.5
+
+- Minimal Luau updated to 0.609
+- Luau max stack size increased to 1M (from 100K)
+- Implemented `IntoLua` for refs to `String`/`Table`/`Function`/`AnyUserData`/`Thread` + `RegistryKey`
+- Implemented `IntoLua` and `FromLua` for `OwnedThread`/`OwnedString`
+- Fixed `FromLua` derive proc macro to cover more cases
+
+## v0.9.4
+
+- Fixed loading all-in-one modules under mixed states (eg. main state and coroutines)
+
 ## v0.9.3
 
 - WebAssembly support (`wasm32-unknown-emscripten` target)

Cargo.toml

@@ -1,8 +1,8 @@
 [package]
 name = "mlua"
-version = "0.9.3" # remember to update mlua_derive
-authors = ["Aleksandr Orlenko <zxteam@pm.me>", "kyren <catherine@chucklefish.org>"]
-rust-version = "1.71"
+version = "0.10.0-beta.2" # 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"
 documentation = "https://docs.rs/mlua"
@@ -16,7 +16,7 @@ with async/await features and support of writing native Lua modules in Rust.
 """
 
 [package.metadata.docs.rs]
-features = ["lua54", "vendored", "async", "send", "serialize", "macros", "parking_lot", "unstable"]
+features = ["lua54", "vendored", "async", "send", "serialize", "macros"]
 rustdoc-args = ["--cfg", "docsrs"]
 
 [workspace]
@@ -32,51 +32,53 @@ lua52 = ["ffi/lua52"]
 lua51 = ["ffi/lua51"]
 luajit = ["ffi/luajit"]
 luajit52 = ["luajit", "ffi/luajit52"]
-luau = ["ffi/luau", "libloading"]
+luau = ["ffi/luau", "dep:libloading"]
 luau-jit = ["luau", "ffi/luau-codegen"]
 luau-vector4 = ["luau", "ffi/luau-vector4"]
 vendored = ["ffi/vendored"]
-module = ["mlua_derive", "ffi/module"]
-async = ["futures-util"]
-send = []
-serialize = ["serde", "erased-serde", "serde-value"]
+module = ["dep:mlua_derive", "ffi/module"]
+async = ["dep:futures-util"]
+send = ["parking_lot/send_guard"]
+serialize = ["dep:serde", "dep:erased-serde", "dep:serde-value"]
 macros = ["mlua_derive/macros"]
-unstable = []
 
 [dependencies]
-mlua_derive = { version = "=0.9.0", optional = true, path = "mlua_derive" }
-bstr = { version = "1.0", features = ["std"], default_features = false }
-once_cell = { version = "1.0" }
+mlua_derive = { version = "=0.10.0-beta.1", optional = true, path = "mlua_derive" }
+bstr = { version = "1.0", features = ["std"], default-features = false }
 num-traits = { version = "0.2.14" }
-rustc-hash = "1.0"
+rustc-hash = "2.0"
 futures-util = { version = "0.3", optional = true, default-features = false, features = ["std"] }
 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", optional = true }
+parking_lot = { version = "0.12", features = ["arc_lock"] }
 
-ffi = { package = "mlua-sys", version = "0.5.0", path = "mlua-sys" }
+ffi = { package = "mlua-sys", version = "0.6.3", path = "mlua-sys" }
 
 [target.'cfg(unix)'.dependencies]
 libloading = { version = "0.8", optional = true }
 
 [dev-dependencies]
 trybuild = "1.0"
-futures = "0.3.5"
-hyper = { version = "0.14", features = ["client", "server"] }
-reqwest = { version = "0.11", features = ["json"] }
+hyper = { version = "1.2", features = ["full"] }
+hyper-util = { version = "0.1.3", features = ["full"] }
+http-body-util = "0.1.1"
+reqwest = { version = "0.12", features = ["json"] }
 tokio = { version = "1.0", features = ["macros", "rt", "time"] }
 serde = { version = "1.0", features = ["derive"] }
-serde_json = "1.0"
+serde_json = { version = "1.0", features = ["arbitrary_precision"] }
 maplit = "1.0"
 tempfile = "3"
 static_assertions = "1.0"
 
 [target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]
 criterion = { version = "0.5", features = ["async_tokio"] }
-rustyline = "13.0"
+rustyline = "14.0"
 tokio = { version = "1.0", features = ["full"] }
 
+[lints.rust]
+unexpected_cfgs = { level = "allow", check-cfg = ['cfg(tarpaulin_include)'] }
+
 [[bench]]
 name = "benchmark"
 harness = false
@@ -97,11 +99,11 @@ required-features = ["async", "serialize", "macros"]
 
 [[example]]
 name = "async_http_server"
-required-features = ["async", "macros"]
+required-features = ["async", "macros", "send"]
 
 [[example]]
 name = "async_tcp_server"
-required-features = ["async", "macros"]
+required-features = ["async", "macros", "send"]
 
 [[example]]
 name = "guided_tour"

README.md

@@ -7,8 +7,8 @@
 [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/khvzak/mlua/branch/master/graph/badge.svg?token=99339FS1CG
-[codecov.io]: https://codecov.io/gh/khvzak/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
 
 [Guided Tour] | [Benchmarks] | [FAQ]
@@ -17,9 +17,7 @@
 [Benchmarks]: https://github.com/khvzak/script-bench-rs
 [FAQ]: FAQ.md
 
-> **Note**
->
-> See v0.9 [release notes](https://github.com/khvzak/mlua/blob/master/docs/release_notes/v0.9.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 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.
@@ -40,23 +38,21 @@ WebAssembly (WASM) is supported through `wasm32-unknown-emscripten` target for a
 `mlua` uses feature flags to reduce the amount of dependencies, 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`: activate Lua [5.4] support
-* `lua53`: activate Lua [5.3] support
-* `lua52`: activate Lua [5.2] support
-* `lua51`: activate Lua [5.1] support
-* `luajit`: activate [LuaJIT] support
-* `luajit52`: activate [LuaJIT] support with partial compatibility with Lua 5.2
-* `luau`: activate [Luau] support (auto vendored mode)
-* `luau-jit`: activate [Luau] support with JIT backend.
-* `luau-vector4`: activate [Luau] support with 4-dimensional vector.
+* `lua54`: enable Lua [5.4] support
+* `lua53`: enable Lua [5.3] support
+* `lua52`: enable Lua [5.2] support
+* `lua51`: enable Lua [5.1] support
+* `luajit`: enable [LuaJIT] support
+* `luajit52`: enable [LuaJIT] support with partial compatibility with Lua 5.2
+* `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
 * `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` transferable across thread boundaries (adds [`Send`] requirement to `mlua::Function` and `mlua::UserData`)
+* `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
 * `macros`: enable procedural macros (such as `chunk!`)
-* `parking_lot`: support UserData types wrapped in [parking_lot]'s primitives (`Arc<Mutex>` and `Arc<RwLock>`)
-* `unstable`: enable **unstable** features. The public API of these features may break between releases.
 
 [5.4]: https://www.lua.org/manual/5.4/manual.html
 [5.3]: https://www.lua.org/manual/5.3/manual.html
@@ -70,7 +66,6 @@ Below is a list of the available feature flags. By default `mlua` does not enabl
 [async-std]: https://github.com/async-rs/async-std
 [`Send`]: https://doc.rust-lang.org/std/marker/trait.Send.html
 [serde]: https://github.com/serde-rs/serde
-[parking_lot]: https://github.com/Amanieu/parking_lot
 
 ### Async/await support
 
@@ -84,6 +79,20 @@ This works using Lua [coroutines](https://www.lua.org/manual/5.3/manual.html#2.6
 - [HTTP Server](examples/async_http_server.rs)
 - [TCP Server](examples/async_tcp_server.rs)
 
+
+**shell command examples**:
+```shell
+# async http client (hyper)
+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
+
+# async http server
+cargo run --example async_http_server --features=lua54,async,macros,send
+curl -v http://localhost:3000
+```
+
 ### Serialization (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).
@@ -119,7 +128,7 @@ Add to `Cargo.toml` :
 
 ``` toml
 [dependencies]
-mlua = { version = "0.9.1", features = ["lua54", "vendored"] }
+mlua = { version = "0.9.9", features = ["lua54", "vendored"] }
 ```
 
 `main.rs`
@@ -154,7 +163,7 @@ Add to `Cargo.toml` :
 crate-type = ["cdylib"]
 
 [dependencies]
-mlua = { version = "0.9.1", features = ["lua54", "module"] }
+mlua = { version = "0.9.9", features = ["lua54", "module"] }
 ```
 
 `lib.rs` :
@@ -184,7 +193,7 @@ $ lua5.4 -e 'require("my_module").hello("world")'
 hello, world!
 ```
 
-On macOS, you need to set additional linker arguments. One option is to compile with `cargo rustc --release -- -C link-arg=-undefined -C link-arg=dynamic_lookup`, the other is to create a `.cargo/config` with the following content:
+On macOS, you need to set additional linker arguments. One option is to compile with `cargo rustc --release -- -C link-arg=-undefined -C link-arg=dynamic_lookup`, the other is to create a `.cargo/config.toml` with the following content:
 ``` toml
 [target.x86_64-apple-darwin]
 rustflags = [
@@ -210,7 +219,11 @@ Module builds don't require Lua lib or headers to be installed on the system.
 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)
 - [`lua-ryaml`](https://github.com/khvzak/lua-ryaml)
+- [`tiktoken_core`](https://github.com/gptlang/lua-tiktoken)
+- [`toml-edit`](https://github.com/vhyrro/toml-edit.lua)
+- [`typst-lua`](https://github.com/rousbound/typst-lua)
 
 [`luarocks-build-rust-mlua`]: https://luarocks.org/modules/khvzak/luarocks-build-rust-mlua
 

benches/benchmark.rs

@@ -1,5 +1,7 @@
-use criterion::{criterion_group, criterion_main, BatchSize, Criterion};
+use std::sync::atomic::{AtomicUsize, Ordering};
 use std::time::Duration;
+
+use criterion::{criterion_group, criterion_main, BatchSize, Criterion};
 use tokio::runtime::Runtime;
 use tokio::task;
 
@@ -10,10 +12,10 @@ fn collect_gc_twice(lua: &Lua) {
     lua.gc_collect().unwrap();
 }
 
-fn create_table(c: &mut Criterion) {
+fn table_create_empty(c: &mut Criterion) {
     let lua = Lua::new();
 
-    c.bench_function("create [table empty]", |b| {
+    c.bench_function("table [create empty]", |b| {
         b.iter_batched(
             || collect_gc_twice(&lua),
             |_| {
@@ -24,35 +26,33 @@ fn create_table(c: &mut Criterion) {
     });
 }
 
-fn create_array(c: &mut Criterion) {
+fn table_create_array(c: &mut Criterion) {
     let lua = Lua::new();
 
-    c.bench_function("create [array] 10", |b| {
+    c.bench_function("table [create array]", |b| {
         b.iter_batched(
             || collect_gc_twice(&lua),
             |_| {
-                let table = lua.create_table().unwrap();
-                for i in 1..=10 {
-                    table.set(i, i).unwrap();
-                }
+                lua.create_sequence_from(1..=10).unwrap();
             },
             BatchSize::SmallInput,
         );
     });
 }
 
-fn create_string_table(c: &mut Criterion) {
+fn table_create_hash(c: &mut Criterion) {
     let lua = Lua::new();
 
-    c.bench_function("create [table string] 10", |b| {
+    c.bench_function("table [create hash]", |b| {
         b.iter_batched(
             || collect_gc_twice(&lua),
             |_| {
-                let table = lua.create_table().unwrap();
-                for &s in &["1", "2", "3", "4", "5", "6", "7", "8", "9", "10"] {
-                    let s = lua.create_string(s).unwrap();
-                    table.set(s.clone(), s).unwrap();
-                }
+                lua.create_table_from(
+                    ["1", "2", "3", "4", "5", "6", "7", "8", "9", "10"]
+                        .into_iter()
+                        .map(|s| (s, s)),
+                )
+                .unwrap();
             },
             BatchSize::SmallInput,
         );
@@ -62,21 +62,19 @@ fn create_string_table(c: &mut Criterion) {
 fn table_get_set(c: &mut Criterion) {
     let lua = Lua::new();
 
-    let table = lua.create_table().unwrap();
-
-    c.bench_function("table raw_get and raw_set [10]", |b| {
+    c.bench_function("table [get and set]", |b| {
         b.iter_batched(
             || {
                 collect_gc_twice(&lua);
-                table.clear().unwrap();
+                lua.create_table().unwrap()
             },
-            |_| {
-                for (i, &s) in ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j"]
-                    .iter()
+            |table| {
+                for (i, s) in ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j"]
+                    .into_iter()
                     .enumerate()
                 {
                     table.raw_set(s, i).unwrap();
-                    assert_eq!(table.raw_get::<_, usize>(s).unwrap(), i);
+                    assert_eq!(table.raw_get::<usize>(s).unwrap(), i);
                 }
             },
             BatchSize::SmallInput,
@@ -87,7 +85,7 @@ fn table_get_set(c: &mut Criterion) {
 fn table_traversal_pairs(c: &mut Criterion) {
     let lua = Lua::new();
 
-    c.bench_function("table traversal [pairs]", |b| {
+    c.bench_function("table [traversal pairs]", |b| {
         b.iter_batched(
             || lua.globals(),
             |globals| {
@@ -103,7 +101,7 @@ fn table_traversal_pairs(c: &mut Criterion) {
 fn table_traversal_for_each(c: &mut Criterion) {
     let lua = Lua::new();
 
-    c.bench_function("table traversal [for_each]", |b| {
+    c.bench_function("table [traversal for_each]", |b| {
         b.iter_batched(
             || lua.globals(),
             |globals| globals.for_each::<String, LuaValue>(|_k, _v| Ok(())),
@@ -117,7 +115,7 @@ fn table_traversal_sequence(c: &mut Criterion) {
 
     let table = lua.create_sequence_from(1..1000).unwrap();
 
-    c.bench_function("table traversal [sequence]", |b| {
+    c.bench_function("table [traversal sequence]", |b| {
         b.iter_batched(
             || table.clone(),
             |table| {
@@ -130,236 +128,257 @@ fn table_traversal_sequence(c: &mut Criterion) {
     });
 }
 
-fn create_function(c: &mut Criterion) {
+fn function_create(c: &mut Criterion) {
     let lua = Lua::new();
 
-    c.bench_function("create [function] 10", |b| {
+    c.bench_function("function [create Rust]", |b| {
         b.iter_batched(
             || collect_gc_twice(&lua),
             |_| {
-                for i in 0..10 {
-                    lua.create_function(move |_, ()| Ok(i)).unwrap();
-                }
+                lua.create_function(|_, ()| Ok(123)).unwrap();
             },
             BatchSize::SmallInput,
         );
     });
 }
 
-fn call_lua_function(c: &mut Criterion) {
+fn function_call_sum(c: &mut Criterion) {
     let lua = Lua::new();
 
-    c.bench_function("call Lua function [sum] 3 10", |b| {
-        b.iter_batched_ref(
-            || {
-                collect_gc_twice(&lua);
-                lua.load("function(a, b, c) return a + b + c end")
-                    .eval::<LuaFunction>()
-                    .unwrap()
-            },
-            |function| {
-                for i in 0..10 {
-                    let _result: i64 = function.call((i, i + 1, i + 2)).unwrap();
-                }
-            },
-            BatchSize::SmallInput,
-        );
-    });
-}
-
-fn call_sum_callback(c: &mut Criterion) {
-    let lua = Lua::new();
-    let callback = lua
-        .create_function(|_, (a, b, c): (i64, i64, i64)| Ok(a + b + c))
+    let sum = lua
+        .create_function(|_, (a, b, c): (i64, i64, i64)| Ok(a + b - c))
         .unwrap();
-    lua.globals().set("callback", callback).unwrap();
 
-    c.bench_function("call Rust callback [sum] 3 10", |b| {
-        b.iter_batched_ref(
-            || {
-                collect_gc_twice(&lua);
-                lua.load("function() for i = 1,10 do callback(i, i+1, i+2) end end")
-                    .eval::<LuaFunction>()
-                    .unwrap()
-            },
-            |function| {
-                function.call::<_, ()>(()).unwrap();
+    c.bench_function("function [call Rust sum]", |b| {
+        b.iter_batched(
+            || collect_gc_twice(&lua),
+            |_| {
+                assert_eq!(sum.call::<i64>((10, 20, 30)).unwrap(), 0);
             },
             BatchSize::SmallInput,
         );
     });
 }
 
-fn call_async_sum_callback(c: &mut Criterion) {
+fn function_call_lua_sum(c: &mut Criterion) {
+    let lua = Lua::new();
+
+    let sum = lua
+        .load("function(a, b, c) return a + b - c end")
+        .eval::<LuaFunction>()
+        .unwrap();
+
+    c.bench_function("function [call Lua sum]", |b| {
+        b.iter_batched(
+            || collect_gc_twice(&lua),
+            |_| {
+                assert_eq!(sum.call::<i64>((10, 20, 30)).unwrap(), 0);
+            },
+            BatchSize::SmallInput,
+        );
+    });
+}
+
+fn function_call_concat(c: &mut Criterion) {
+    let lua = Lua::new();
+
+    let concat = lua
+        .create_function(|_, (a, b): (LuaString, LuaString)| Ok(format!("{}{}", a.to_str()?, b.to_str()?)))
+        .unwrap();
+    let i = AtomicUsize::new(0);
+
+    c.bench_function("function [call Rust concat string]", |b| {
+        b.iter_batched(
+            || {
+                collect_gc_twice(&lua);
+                i.fetch_add(1, Ordering::Relaxed)
+            },
+            |i| {
+                assert_eq!(concat.call::<LuaString>(("num:", i)).unwrap(), format!("num:{i}"));
+            },
+            BatchSize::SmallInput,
+        );
+    });
+}
+
+fn function_call_lua_concat(c: &mut Criterion) {
+    let lua = Lua::new();
+
+    let concat = lua
+        .load("function(a, b) return a..b end")
+        .eval::<LuaFunction>()
+        .unwrap();
+    let i = AtomicUsize::new(0);
+
+    c.bench_function("function [call Lua concat string]", |b| {
+        b.iter_batched(
+            || {
+                collect_gc_twice(&lua);
+                i.fetch_add(1, Ordering::Relaxed)
+            },
+            |i| {
+                assert_eq!(concat.call::<LuaString>(("num:", i)).unwrap(), format!("num:{i}"));
+            },
+            BatchSize::SmallInput,
+        );
+    });
+}
+
+fn function_async_call_sum(c: &mut Criterion) {
     let options = LuaOptions::new().thread_pool_size(1024);
     let lua = Lua::new_with(LuaStdLib::ALL_SAFE, options).unwrap();
-    let callback = lua
+
+    let sum = lua
         .create_async_function(|_, (a, b, c): (i64, i64, i64)| async move {
             task::yield_now().await;
-            Ok(a + b + c)
+            Ok(a + b - c)
         })
         .unwrap();
-    lua.globals().set("callback", callback).unwrap();
 
-    c.bench_function("call async Rust callback [sum] 3 10", |b| {
+    c.bench_function("function [async call Rust sum]", |b| {
         let rt = Runtime::new().unwrap();
         b.to_async(rt).iter_batched(
-            || {
-                collect_gc_twice(&lua);
-                lua.load("function() for i = 1,10 do callback(i, i+1, i+2) end end")
-                    .eval::<LuaFunction>()
-                    .unwrap()
-            },
-            |function| async move {
-                function.call_async::<_, ()>(()).await.unwrap();
+            || collect_gc_twice(&lua),
+            |_| async {
+                assert_eq!(sum.call_async::<i64>((10, 20, 30)).await.unwrap(), 0);
             },
             BatchSize::SmallInput,
         );
     });
 }
 
-fn call_concat_callback(c: &mut Criterion) {
+fn registry_value_create(c: &mut Criterion) {
     let lua = Lua::new();
-    let callback = lua
-        .create_function(|_, (a, b): (LuaString, LuaString)| {
-            Ok(format!("{}{}", a.to_str()?, b.to_str()?))
-        })
-        .unwrap();
-    lua.globals().set("callback", callback).unwrap();
+    lua.gc_stop();
 
-    c.bench_function("call Rust callback [concat string] 10", |b| {
-        b.iter_batched_ref(
-            || {
-                collect_gc_twice(&lua);
-                lua.load("function() for i = 1,10 do callback('a', tostring(i)) end end")
-                    .eval::<LuaFunction>()
-                    .unwrap()
-            },
-            |function| {
-                function.call::<_, ()>(()).unwrap();
-            },
+    c.bench_function("registry value [create]", |b| {
+        b.iter_batched(
+            || collect_gc_twice(&lua),
+            |_| lua.create_registry_value("hello").unwrap(),
             BatchSize::SmallInput,
         );
     });
 }
 
-fn create_registry_values(c: &mut Criterion) {
+fn registry_value_get(c: &mut Criterion) {
     let lua = Lua::new();
+    lua.gc_stop();
 
-    c.bench_function("create [registry value] 10", |b| {
+    let value = lua.create_registry_value("hello").unwrap();
+
+    c.bench_function("registry value [get]", |b| {
         b.iter_batched(
             || collect_gc_twice(&lua),
             |_| {
-                for _ in 0..10 {
-                    lua.create_registry_value(lua.pack(true).unwrap()).unwrap();
-                }
-                lua.expire_registry_values();
+                assert_eq!(lua.registry_value::<LuaString>(&value).unwrap(), "hello");
             },
             BatchSize::SmallInput,
         );
     });
 }
 
-fn create_userdata(c: &mut Criterion) {
-    struct UserData(i64);
+fn userdata_create(c: &mut Criterion) {
+    struct UserData(#[allow(unused)] i64);
     impl LuaUserData for UserData {}
 
     let lua = Lua::new();
 
-    c.bench_function("create [table userdata] 10", |b| {
+    c.bench_function("userdata [create]", |b| {
         b.iter_batched(
             || collect_gc_twice(&lua),
             |_| {
-                let table: LuaTable = lua.create_table().unwrap();
-                for i in 1..11 {
-                    table.set(i, UserData(i)).unwrap();
-                }
+                lua.create_userdata(UserData(123)).unwrap();
             },
             BatchSize::SmallInput,
         );
     });
 }
 
-fn call_userdata_index(c: &mut Criterion) {
-    struct UserData(i64);
+fn userdata_call_index(c: &mut Criterion) {
+    struct UserData(#[allow(unused)] i64);
     impl LuaUserData for UserData {
-        fn add_methods<'lua, M: LuaUserDataMethods<'lua, Self>>(methods: &mut M) {
-            methods.add_meta_method(LuaMetaMethod::Index, move |_, _, index: String| Ok(index));
+        fn add_methods<M: LuaUserDataMethods<Self>>(methods: &mut M) {
+            methods.add_meta_method(LuaMetaMethod::Index, move |_, _, key: LuaString| Ok(key));
         }
     }
 
     let lua = Lua::new();
-    lua.globals().set("userdata", UserData(10)).unwrap();
+    let ud = lua.create_userdata(UserData(123)).unwrap();
+    let index = lua
+        .load("function(ud) return ud.test end")
+        .eval::<LuaFunction>()
+        .unwrap();
 
-    c.bench_function("call [userdata index] 10", |b| {
-        b.iter_batched_ref(
-            || {
-                collect_gc_twice(&lua);
-                lua.load("function() for i = 1,10 do local v = userdata.test end end")
-                    .eval::<LuaFunction>()
-                    .unwrap()
-            },
-            |function| {
-                function.call::<_, ()>(()).unwrap();
+    c.bench_function("userdata [call index]", |b| {
+        b.iter_batched(
+            || collect_gc_twice(&lua),
+            |_| {
+                assert_eq!(index.call::<LuaString>(&ud).unwrap(), "test");
             },
             BatchSize::SmallInput,
         );
     });
 }
 
-fn call_userdata_method(c: &mut Criterion) {
+fn userdata_call_method(c: &mut Criterion) {
     struct UserData(i64);
     impl LuaUserData for UserData {
-        fn add_methods<'lua, M: LuaUserDataMethods<'lua, Self>>(methods: &mut M) {
-            methods.add_method("method", |_, this, ()| Ok(this.0));
+        fn add_methods<M: LuaUserDataMethods<Self>>(methods: &mut M) {
+            methods.add_method("add", |_, this, i: i64| Ok(this.0 + i));
         }
     }
 
     let lua = Lua::new();
-    lua.globals().set("userdata", UserData(10)).unwrap();
+    let ud = lua.create_userdata(UserData(123)).unwrap();
+    let method = lua
+        .load("function(ud, i) return ud:add(i) end")
+        .eval::<LuaFunction>()
+        .unwrap();
+    let i = AtomicUsize::new(0);
 
-    c.bench_function("call [userdata method] 10", |b| {
-        b.iter_batched_ref(
+    c.bench_function("userdata [call method]", |b| {
+        b.iter_batched(
             || {
                 collect_gc_twice(&lua);
-                lua.load("function() for i = 1,10 do userdata:method() end end")
-                    .eval::<LuaFunction>()
-                    .unwrap()
+                i.fetch_add(1, Ordering::Relaxed)
             },
-            |function| {
-                function.call::<_, ()>(()).unwrap();
+            |i| {
+                assert_eq!(method.call::<usize>((&ud, i)).unwrap(), 123 + i);
             },
             BatchSize::SmallInput,
         );
     });
 }
 
-fn call_async_userdata_method(c: &mut Criterion) {
-    struct UserData(String);
-
+fn userdata_async_call_method(c: &mut Criterion) {
+    struct UserData(i64);
     impl LuaUserData for UserData {
-        fn add_methods<'lua, M: LuaUserDataMethods<'lua, Self>>(methods: &mut M) {
-            methods.add_async_method("method", |_, this, ()| async move { Ok(this.0.clone()) });
+        fn add_methods<M: LuaUserDataMethods<Self>>(methods: &mut M) {
+            methods.add_async_method("add", |_, this, i: i64| async move {
+                task::yield_now().await;
+                Ok(this.0 + i)
+            });
         }
     }
 
     let options = LuaOptions::new().thread_pool_size(1024);
     let lua = Lua::new_with(LuaStdLib::ALL_SAFE, options).unwrap();
-    lua.globals()
-        .set("userdata", UserData("hello".to_string()))
+    let ud = lua.create_userdata(UserData(123)).unwrap();
+    let method = lua
+        .load("function(ud, i) return ud:add(i) end")
+        .eval::<LuaFunction>()
         .unwrap();
+    let i = AtomicUsize::new(0);
 
-    c.bench_function("call async [userdata method] 10", |b| {
+    c.bench_function("userdata [async call method] 10", |b| {
         let rt = Runtime::new().unwrap();
         b.to_async(rt).iter_batched(
             || {
                 collect_gc_twice(&lua);
-                lua.load("function() for i = 1,10 do userdata:method() end end")
-                    .eval::<LuaFunction>()
-                    .unwrap()
+                (method.clone(), ud.clone(), i.fetch_add(1, Ordering::Relaxed))
             },
-            |function| async move {
-                function.call_async::<_, ()>(()).await.unwrap();
+            |(method, ud, i)| async move {
+                assert_eq!(method.call_async::<usize>((ud, i)).await.unwrap(), 123 + i);
             },
             BatchSize::SmallInput,
         );
@@ -369,27 +388,32 @@ fn call_async_userdata_method(c: &mut Criterion) {
 criterion_group! {
     name = benches;
     config = Criterion::default()
-        .sample_size(300)
+        .sample_size(500)
         .measurement_time(Duration::from_secs(10))
         .noise_threshold(0.02);
     targets =
-        create_table,
-        create_array,
-        create_string_table,
+        table_create_empty,
+        table_create_array,
+        table_create_hash,
         table_get_set,
         table_traversal_pairs,
         table_traversal_for_each,
         table_traversal_sequence,
-        create_function,
-        call_lua_function,
-        call_sum_callback,
-        call_async_sum_callback,
-        call_concat_callback,
-        create_registry_values,
-        create_userdata,
-        call_userdata_index,
-        call_userdata_method,
-        call_async_userdata_method,
+
+        function_create,
+        function_call_sum,
+        function_call_lua_sum,
+        function_call_concat,
+        function_call_lua_concat,
+        function_async_call_sum,
+
+        registry_value_create,
+        registry_value_get,
+
+        userdata_create,
+        userdata_call_index,
+        userdata_call_method,
+        userdata_async_call_method,
 }
 
 criterion_main!(benches);

benches/serde.rs

@@ -1,6 +1,7 @@
-use criterion::{criterion_group, criterion_main, BatchSize, Criterion};
 use std::time::Duration;
 
+use criterion::{criterion_group, criterion_main, BatchSize, Criterion};
+
 use mlua::prelude::*;
 
 fn collect_gc_twice(lua: &Lua) {
@@ -8,43 +9,67 @@ fn collect_gc_twice(lua: &Lua) {
     lua.gc_collect().unwrap();
 }
 
-fn serialize_json(c: &mut Criterion) {
+fn encode_json(c: &mut Criterion) {
     let lua = Lua::new();
 
-    lua.globals()
-        .set(
-            "encode",
-            LuaFunction::wrap(|_, t: LuaValue| Ok(serde_json::to_string(&t).unwrap())),
+    let encode = lua
+        .create_function(|_, t: LuaValue| Ok(serde_json::to_string(&t).unwrap()))
+        .unwrap();
+    let table = lua
+        .load(
+            r#"{
+        name = "Clark Kent",
+        address = {
+            city = "Smallville",
+            state = "Kansas",
+            country = "USA",
+        },
+        age = 22,
+        parents = {"Jonathan Kent", "Martha Kent"},
+        superman = true,
+        interests = {"flying", "saving the world", "kryptonite"},
+    }"#,
         )
+        .eval::<LuaTable>()
         .unwrap();
 
-    c.bench_function("serialize table to json [10]", |b| {
+    c.bench_function("serialize json", |b| {
         b.iter_batched(
-            || {
-                collect_gc_twice(&lua);
-                lua.load(
-                    r#"
-                local encode = encode
-                return function()
-                    for i = 1, 10 do
-                        encode({
-                            name = "Clark Kent",
-                            nickname = "Superman",
-                            address = {
-                                city = "Metropolis",
-                            },
-                            age = 32,
-                            superman = true,
-                        })
-                    end
-                end
-            "#,
-                )
-                .eval::<LuaFunction>()
-                .unwrap()
+            || collect_gc_twice(&lua),
+            |_| {
+                encode.call::<LuaString>(&table).unwrap();
             },
-            |func| {
-                func.call::<_, ()>(()).unwrap();
+            BatchSize::SmallInput,
+        );
+    });
+}
+
+fn decode_json(c: &mut Criterion) {
+    let lua = Lua::new();
+
+    let decode = lua
+        .create_function(|lua, s: String| {
+            lua.to_value(&serde_json::from_str::<serde_json::Value>(&s).unwrap())
+        })
+        .unwrap();
+    let json = r#"{
+        "name": "Clark Kent",
+        "address": {
+            "city": "Smallville",
+            "state": "Kansas",
+            "country": "USA"
+        },
+        "age": 22,
+        "parents": ["Jonathan Kent", "Martha Kent"],
+        "superman": true,
+        "interests": ["flying", "saving the world", "kryptonite"]
+    }"#;
+
+    c.bench_function("deserialize json", |b| {
+        b.iter_batched(
+            || collect_gc_twice(&lua),
+            |_| {
+                decode.call::<LuaTable>(json).unwrap();
             },
             BatchSize::SmallInput,
         );
@@ -54,11 +79,12 @@ fn serialize_json(c: &mut Criterion) {
 criterion_group! {
     name = benches;
     config = Criterion::default()
-        .sample_size(300)
+        .sample_size(500)
         .measurement_time(Duration::from_secs(10))
         .noise_threshold(0.02);
     targets =
-        serialize_json,
+        encode_json,
+        decode_json,
 }
 
 criterion_main!(benches);

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/master/CHANGELOG.md
+[CHANGELOG]: https://github.com/khvzak/mlua/blob/main/CHANGELOG.md
 
 ### New features
 

examples/async_http_client.rs

@@ -1,18 +1,22 @@
 use std::collections::HashMap;
 
-use hyper::body::{Body as HyperBody, HttpBody as _};
-use hyper::Client as HyperClient;
+use http_body_util::BodyExt as _;
+use hyper::body::Incoming;
+use hyper_util::client::legacy::Client as HyperClient;
+use hyper_util::rt::TokioExecutor;
 
 use mlua::{chunk, ExternalResult, Lua, Result, UserData, UserDataMethods};
 
-struct BodyReader(HyperBody);
+struct BodyReader(Incoming);
 
 impl UserData for BodyReader {
-    fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
-        methods.add_async_method_mut("read", |lua, reader, ()| async move {
-            if let Some(bytes) = reader.0.data().await {
-                let bytes = bytes.into_lua_err()?;
-                return Some(lua.create_string(&bytes)).transpose();
+    fn add_methods<M: UserDataMethods<Self>>(methods: &mut M) {
+        // Every call returns a next chunk
+        methods.add_async_method_mut("read", |lua, mut reader, ()| async move {
+            if let Some(bytes) = reader.0.frame().await {
+                if let Some(bytes) = bytes.into_lua_err()?.data_ref() {
+                    return Some(lua.create_string(&bytes)).transpose();
+                }
             }
             Ok(None)
         });
@@ -24,7 +28,7 @@ async fn main() -> Result<()> {
     let lua = Lua::new();
 
     let fetch_url = lua.create_async_function(|lua, uri: String| async move {
-        let client = HyperClient::new();
+        let client = HyperClient::builder(TokioExecutor::new()).build_http::<String>();
         let uri = uri.parse().into_lua_err()?;
         let resp = client.get(uri).await.into_lua_err()?;
 
@@ -55,11 +59,11 @@ async fn main() -> Result<()> {
                 end
             end
             repeat
-                local body = res.body:read()
-                if body then
-                    print(body)
+                local chunk = res.body:read()
+                if chunk then
+                    print(chunk)
                 end
-            until not body
+            until not chunk
         })
         .into_function()?;
 

examples/async_http_reqwest.rs

@@ -1,11 +1,9 @@
-use mlua::{chunk, ExternalResult, Lua, LuaSerdeExt, Result};
+use mlua::{chunk, ExternalResult, Lua, LuaSerdeExt, Result, Value};
 
 #[tokio::main(flavor = "current_thread")]
 async fn main() -> Result<()> {
     let lua = Lua::new();
 
-    let null = lua.null();
-
     let fetch_json = lua.create_async_function(|lua, uri: String| async move {
         let resp = reqwest::get(&uri)
             .await
@@ -15,19 +13,15 @@ async fn main() -> Result<()> {
         lua.to_value(&json)
     })?;
 
+    let dbg = lua.create_function(|_, value: Value| {
+        println!("{value:#?}");
+        Ok(())
+    })?;
+
     let f = lua
         .load(chunk! {
-            function print_r(t, indent)
-                local indent = indent or ""
-                for k, v in pairs(t) do
-                    io.write(indent, tostring(k))
-                    if type(v) == "table" then io.write(":\n") print_r(v, indent.."  ")
-                    else io.write(": ", v == $null and "null" or tostring(v), "\n") end
-                end
-            end
-
             local res = $fetch_json(...)
-            print_r(res)
+            $dbg(res)
         })
         .into_function()?;
 

examples/async_http_server.rs

@@ -1,60 +1,70 @@
+use std::convert::Infallible;
 use std::future::Future;
 use std::net::SocketAddr;
 use std::pin::Pin;
-use std::rc::Rc;
-use std::task::{Context, Poll};
 
-use hyper::server::conn::AddrStream;
-use hyper::service::Service;
-use hyper::{Body, Request, Response, Server};
+use http_body_util::combinators::BoxBody;
+use http_body_util::{BodyExt as _, Empty, Full};
+use hyper::body::{Bytes, Incoming};
+use hyper::server::conn::http1;
+use hyper::{Request, Response};
+use hyper_util::rt::TokioIo;
+use tokio::net::TcpListener;
 
-use mlua::{
-    chunk, Error as LuaError, Function, Lua, String as LuaString, Table, UserData, UserDataMethods,
-};
+use mlua::{chunk, Error as LuaError, Function, Lua, String as LuaString, Table, UserData, UserDataMethods};
 
-struct LuaRequest(SocketAddr, Request<Body>);
+/// Wrapper around incoming request that implements UserData
+struct LuaRequest(SocketAddr, Request<Incoming>);
 
 impl UserData for LuaRequest {
-    fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
-        methods.add_method("remote_addr", |_lua, req, ()| Ok((req.0).to_string()));
-        methods.add_method("method", |_lua, req, ()| Ok((req.1).method().to_string()));
+    fn add_methods<M: UserDataMethods<Self>>(methods: &mut M) {
+        methods.add_method("remote_addr", |_, req, ()| Ok((req.0).to_string()));
+        methods.add_method("method", |_, req, ()| Ok((req.1).method().to_string()));
+        methods.add_method("path", |_, req, ()| Ok(req.1.uri().path().to_string()));
     }
 }
 
-pub struct Svc(Rc<Lua>, SocketAddr);
+/// Service that handles incoming requests
+#[derive(Clone)]
+pub struct Svc {
+    handler: Function,
+    peer_addr: SocketAddr,
+}
 
-impl Service<Request<Body>> for Svc {
-    type Response = Response<Body>;
-    type Error = LuaError;
-    type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>>>>;
-
-    fn poll_ready(&mut self, _cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
-        Poll::Ready(Ok(()))
+impl Svc {
+    pub fn new(handler: Function, peer_addr: SocketAddr) -> Self {
+        Self { handler, peer_addr }
     }
+}
 
-    fn call(&mut self, req: Request<Body>) -> Self::Future {
+impl hyper::service::Service<Request<Incoming>> for Svc {
+    type Response = Response<BoxBody<Bytes, Infallible>>;
+    type Error = LuaError;
+    type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>> + Send>>;
+
+    fn call(&self, req: Request<Incoming>) -> Self::Future {
         // If handler returns an error then generate 5xx response
-        let lua = self.0.clone();
-        let lua_req = LuaRequest(self.1, req);
+        let handler = self.handler.clone();
+        let lua_req = LuaRequest(self.peer_addr, req);
         Box::pin(async move {
-            let handler: Function = lua.named_registry_value("http_handler")?;
-            match handler.call_async::<_, Table>(lua_req).await {
+            match handler.call_async::<Table>(lua_req).await {
                 Ok(lua_resp) => {
-                    let status = lua_resp.get::<_, Option<u16>>("status")?.unwrap_or(200);
+                    let status = lua_resp.get::<Option<u16>>("status")?.unwrap_or(200);
                     let mut resp = Response::builder().status(status);
 
                     // Set headers
-                    if let Some(headers) = lua_resp.get::<_, Option<Table>>("headers")? {
+                    if let Some(headers) = lua_resp.get::<Option<Table>>("headers")? {
                         for pair in headers.pairs::<String, LuaString>() {
                             let (h, v) = pair?;
-                            resp = resp.header(&h, v.as_bytes());
+                            resp = resp.header(&h, &*v.as_bytes());
                         }
                     }
 
+                    // Set body
                     let body = lua_resp
-                        .get::<_, Option<LuaString>>("body")?
-                        .map(|b| Body::from(b.as_bytes().to_vec()))
-                        .unwrap_or_else(Body::empty);
+                        .get::<Option<LuaString>>("body")?
+                        .map(|b| Full::new(Bytes::copy_from_slice(&b.as_bytes())).boxed())
+                        .unwrap_or_else(|| Empty::<Bytes>::new().boxed());
 
                     Ok(resp.body(body).unwrap())
                 }
@@ -62,7 +72,7 @@ impl Service<Request<Body>> for Svc {
                     eprintln!("{}", err);
                     Ok(Response::builder()
                         .status(500)
-                        .body(Body::from("Internal Server Error"))
+                        .body(Full::new(Bytes::from("Internal Server Error")).boxed())
                         .unwrap())
                 }
             }
@@ -72,65 +82,47 @@ impl Service<Request<Body>> for Svc {
 
 #[tokio::main(flavor = "current_thread")]
 async fn main() {
-    let lua = Rc::new(Lua::new());
+    let lua = Lua::new();
 
     // Create Lua handler function
-    let handler: Function = lua
+    let handler = lua
         .load(chunk! {
             function(req)
                 return {
                     status = 200,
                     headers = {
                         ["X-Req-Method"] = req:method(),
+                        ["X-Req-Path"] = req:path(),
                         ["X-Remote-Addr"] = req:remote_addr(),
                     },
                     body = "Hello from Lua!\n"
                 }
             end
         })
-        .eval()
-        .expect("cannot create Lua handler");
+        .eval::<Function>()
+        .expect("Failed to create Lua handler");
 
-    // Store it in the Registry
-    lua.set_named_registry_value("http_handler", handler)
-        .expect("cannot store Lua handler");
+    let listen_addr = "127.0.0.1:3000";
+    let listener = TcpListener::bind(listen_addr).await.unwrap();
+    println!("Listening on http://{listen_addr}");
 
-    let addr = ([127, 0, 0, 1], 3000).into();
-    let server = Server::bind(&addr).executor(LocalExec).serve(MakeSvc(lua));
+    loop {
+        let (stream, peer_addr) = match listener.accept().await {
+            Ok(x) => x,
+            Err(err) => {
+                eprintln!("Failed to accept connection: {err}");
+                continue;
+            }
+        };
 
-    println!("Listening on http://{}", addr);
-
-    // Create `LocalSet` to spawn !Send futures
-    let local = tokio::task::LocalSet::new();
-    local.run_until(server).await.expect("cannot run server")
-}
-
-struct MakeSvc(Rc<Lua>);
-
-impl Service<&AddrStream> for MakeSvc {
-    type Response = Svc;
-    type Error = hyper::Error;
-    type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>>>>;
-
-    fn poll_ready(&mut self, _: &mut Context) -> Poll<Result<(), Self::Error>> {
-        Poll::Ready(Ok(()))
-    }
-
-    fn call(&mut self, stream: &AddrStream) -> Self::Future {
-        let lua = self.0.clone();
-        let remote_addr = stream.remote_addr();
-        Box::pin(async move { Ok(Svc(lua, remote_addr)) })
-    }
-}
-
-#[derive(Clone, Copy, Debug)]
-struct LocalExec;
-
-impl<F> hyper::rt::Executor<F> for LocalExec
-where
-    F: std::future::Future + 'static, // not requiring `Send`
-{
-    fn execute(&self, fut: F) {
-        tokio::task::spawn_local(fut);
+        let svc = Svc::new(handler.clone(), peer_addr);
+        tokio::task::spawn(async move {
+            if let Err(err) = http1::Builder::new()
+                .serve_connection(TokioIo::new(stream), svc)
+                .await
+            {
+                eprintln!("Error serving connection: {:?}", err);
+            }
+        });
     }
 }

examples/async_tcp_server.rs

@@ -1,48 +1,42 @@
 use std::io;
 use std::net::SocketAddr;
-use std::rc::Rc;
 
 use tokio::io::{AsyncReadExt, AsyncWriteExt};
 use tokio::net::{TcpListener, TcpStream};
-use tokio::task;
 
-use mlua::{chunk, Function, Lua, RegistryKey, String as LuaString, UserData, UserDataMethods};
+use mlua::{chunk, BString, Function, Lua, UserData, UserDataMethods};
 
 struct LuaTcpStream(TcpStream);
 
 impl UserData for LuaTcpStream {
-    fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
-        methods.add_method("peer_addr", |_, this, ()| {
-            Ok(this.0.peer_addr()?.to_string())
-        });
+    fn add_methods<M: UserDataMethods<Self>>(methods: &mut M) {
+        methods.add_method("peer_addr", |_, this, ()| Ok(this.0.peer_addr()?.to_string()));
 
-        methods.add_async_method_mut("read", |lua, this, size| async move {
+        methods.add_async_method_mut("read", |lua, mut this, size| async move {
             let mut buf = vec![0; size];
             let n = this.0.read(&mut buf).await?;
             buf.truncate(n);
             lua.create_string(&buf)
         });
 
-        methods.add_async_method_mut("write", |_, this, data: LuaString| async move {
-            let n = this.0.write(&data.as_bytes()).await?;
+        methods.add_async_method_mut("write", |_, mut this, data: BString| async move {
+            let n = this.0.write(&data).await?;
             Ok(n)
         });
 
-        methods.add_async_method_mut("close", |_, this, ()| async move {
+        methods.add_async_method_mut("close", |_, mut this, ()| async move {
             this.0.shutdown().await?;
             Ok(())
         });
     }
 }
 
-async fn run_server(lua: Lua, handler: RegistryKey) -> io::Result<()> {
+async fn run_server(handler: Function) -> io::Result<()> {
     let addr: SocketAddr = ([127, 0, 0, 1], 3000).into();
     let listener = TcpListener::bind(addr).await.expect("cannot bind addr");
 
     println!("Listening on {}", addr);
 
-    let lua = Rc::new(lua);
-    let handler = Rc::new(handler);
     loop {
         let (stream, _) = match listener.accept().await {
             Ok(res) => res,
@@ -50,15 +44,10 @@ async fn run_server(lua: Lua, handler: RegistryKey) -> io::Result<()> {
             Err(err) => return Err(err),
         };
 
-        let lua = lua.clone();
         let handler = handler.clone();
-        task::spawn_local(async move {
-            let handler: Function = lua
-                .registry_value(&handler)
-                .expect("cannot get Lua handler");
-
+        tokio::task::spawn(async move {
             let stream = LuaTcpStream(stream);
-            if let Err(err) = handler.call_async::<_, ()>(stream).await {
+            if let Err(err) = handler.call_async::<()>(stream).await {
                 eprintln!("{}", err);
             }
         });
@@ -70,7 +59,7 @@ async fn main() {
     let lua = Lua::new();
 
     // Create Lua handler function
-    let handler_fn = lua
+    let handler = lua
         .load(chunk! {
             function(stream)
                 local peer_addr = stream:peer_addr()
@@ -92,15 +81,7 @@ async fn main() {
         .eval::<Function>()
         .expect("cannot create Lua handler");
 
-    // Store it in the Registry
-    let handler = lua
-        .create_registry_value(handler_fn)
-        .expect("cannot store Lua handler");
-
-    task::LocalSet::new()
-        .run_until(run_server(lua, handler))
-        .await
-        .expect("cannot run server")
+    run_server(handler).await.expect("cannot run server")
 }
 
 fn is_transient_error(e: &io::Error) -> bool {

examples/guided_tour.rs

@@ -1,9 +1,7 @@
 use std::f32;
 use std::iter::FromIterator;
 
-use mlua::{
-    chunk, FromLua, Function, Lua, MetaMethod, Result, UserData, UserDataMethods, Value, Variadic,
-};
+use mlua::{chunk, FromLua, Function, Lua, MetaMethod, Result, UserData, UserDataMethods, Value, Variadic};
 
 fn main() -> Result<()> {
     // You can create a new Lua state with `Lua::new()`. This loads the default Lua std library
@@ -19,12 +17,12 @@ fn main() -> Result<()> {
     globals.set("string_var", "hello")?;
     globals.set("int_var", 42)?;
 
-    assert_eq!(globals.get::<_, String>("string_var")?, "hello");
-    assert_eq!(globals.get::<_, i64>("int_var")?, 42);
+    assert_eq!(globals.get::<String>("string_var")?, "hello");
+    assert_eq!(globals.get::<i64>("int_var")?, 42);
 
     // You can load and evaluate Lua code. The returned type of `Lua::load` is a builder
     // that allows you to change settings before running Lua code. Here, we are using it to set
-    // the name of the laoded chunk to "example code", which will be used when Lua error
+    // the name of the loaded chunk to "example code", which will be used when Lua error
     // messages are printed.
 
     lua.load(
@@ -34,7 +32,7 @@ fn main() -> Result<()> {
     )
     .set_name("example code")
     .exec()?;
-    assert_eq!(globals.get::<_, String>("global")?, "foobar");
+    assert_eq!(globals.get::<String>("global")?, "foobar");
 
     assert_eq!(lua.load("1 + 1").eval::<i32>()?, 2);
     assert_eq!(lua.load("false == false").eval::<bool>()?, true);
@@ -87,20 +85,20 @@ fn main() -> Result<()> {
     // You can load Lua functions
 
     let print: Function = globals.get("print")?;
-    print.call::<_, ()>("hello from rust")?;
+    print.call::<()>("hello from rust")?;
 
-    // This API generally handles variadics using tuples. This is one way to call a function with
+    // This API generally handles variadic using tuples. This is one way to call a function with
     // multiple parameters:
 
-    print.call::<_, ()>(("hello", "again", "from", "rust"))?;
+    print.call::<()>(("hello", "again", "from", "rust"))?;
 
     // But, you can also pass variadic arguments with the `Variadic` type.
 
-    print.call::<_, ()>(Variadic::from_iter(
+    print.call::<()>(Variadic::from_iter(
         ["hello", "yet", "again", "from", "rust"].iter().cloned(),
     ))?;
 
-    // You can bind rust functions to Lua as well. Callbacks receive the Lua state inself as their
+    // You can bind rust functions to Lua as well. Callbacks receive the Lua state itself as their
     // first parameter, and the arguments given to the function as the second parameter. The type
     // of the arguments can be anything that is convertible from the parameters given by Lua, in
     // this case, the function expects two string sequences.
@@ -154,8 +152,8 @@ fn main() -> Result<()> {
     struct Vec2(f32, f32);
 
     // We can implement `FromLua` trait for our `Vec2` to return a copy
-    impl<'lua> FromLua<'lua> for Vec2 {
-        fn from_lua(value: Value<'lua>, _: &'lua Lua) -> Result<Self> {
+    impl FromLua for Vec2 {
+        fn from_lua(value: Value, _: &Lua) -> Result<Self> {
             match value {
                 Value::UserData(ud) => Ok(*ud.borrow::<Self>()?),
                 _ => unreachable!(),
@@ -164,7 +162,7 @@ fn main() -> Result<()> {
     }
 
     impl UserData for Vec2 {
-        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+        fn add_methods<M: UserDataMethods<Self>>(methods: &mut M) {
             methods.add_method("magnitude", |_, vec, ()| {
                 let mag_squared = vec.0 * vec.0 + vec.1 * vec.1;
                 Ok(mag_squared.sqrt())
@@ -179,19 +177,15 @@ fn main() -> Result<()> {
     let vec2_constructor = lua.create_function(|_, (x, y): (f32, f32)| Ok(Vec2(x, y)))?;
     globals.set("vec2", vec2_constructor)?;
 
-    assert!(
-        (lua.load("(vec2(1, 2) + vec2(2, 2)):magnitude()")
-            .eval::<f32>()?
-            - 5.0)
-            .abs()
-            < f32::EPSILON
-    );
+    assert!((lua.load("(vec2(1, 2) + vec2(2, 2)):magnitude()").eval::<f32>()? - 5.0).abs() < f32::EPSILON);
 
     // Normally, Rust types passed to `Lua` must be `'static`, because there is no way to be
     // sure of their lifetime inside the Lua state. There is, however, a limited way to lift this
     // requirement. You can call `Lua::scope` to create userdata and callbacks types that only live
     // for as long as the call to scope, but do not have to be `'static` (and `Send`).
 
+    // TODO: Re-enable this
+    /*
     {
         let mut rust_val = 0;
 
@@ -213,6 +207,7 @@ fn main() -> Result<()> {
 
         assert_eq!(rust_val, 42);
     }
+    */
 
     // We were able to run our 'sketchy' function inside the scope just fine. However, if we
     // try to run our 'sketchy' function outside of the scope, the function we created will have

examples/serialize.rs

@@ -28,9 +28,14 @@ fn main() -> Result<()> {
     let globals = lua.globals();
 
     // Create Car struct from a Lua table
-    let car: Car = lua.from_value(lua.load(r#"
+    let car: Car = lua.from_value(
+        lua.load(
+            r#"
         {active = true, model = "Volkswagen Golf", transmission = "Automatic", engine = {v = 1499, kw = 90}}
-    "#).eval()?)?;
+    "#,
+        )
+        .eval()?,
+    )?;
 
     // Set it as (serializable) userdata
     globals.set("null", lua.null())?;

examples/userdata.rs

@@ -7,7 +7,7 @@ struct Rectangle {
 }
 
 impl UserData for Rectangle {
-    fn add_fields<'lua, F: mlua::UserDataFields<'lua, Self>>(fields: &mut F) {
+    fn add_fields<F: mlua::UserDataFields<Self>>(fields: &mut F) {
         fields.add_field_method_get("length", |_, this| Ok(this.length));
         fields.add_field_method_set("length", |_, this, val| {
             this.length = val;
@@ -20,7 +20,7 @@ impl UserData for Rectangle {
         });
     }
 
-    fn add_methods<'lua, M: mlua::UserDataMethods<'lua, Self>>(methods: &mut M) {
+    fn add_methods<M: mlua::UserDataMethods<Self>>(methods: &mut M) {
         methods.add_method("area", |_, this, ()| Ok(this.length * this.width));
         methods.add_method("diagonal", |_, this, ()| {
             Ok((this.length.pow(2) as f64 + this.width.pow(2) as f64).sqrt())

mlua-sys/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mlua-sys"
-version = "0.5.0"
+version = "0.6.3"
 authors = ["Aleksandr Orlenko <zxteam@pm.me>"]
 rust-version = "1.71"
 edition = "2021"
@@ -38,6 +38,9 @@ module = []
 cc = "1.0"
 cfg-if = "1.0"
 pkg-config = "0.3.17"
-lua-src = { version = ">= 546.0.2, < 546.1.0", optional = true }
+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 = "0.7.11", optional = true }
+luau0-src = { version = "0.10.0", optional = true }
+
+[lints.rust]
+unexpected_cfgs = { level = "allow", check-cfg = ['cfg(raw_dylib)'] }

mlua-sys/build/find_vendored.rs

@@ -21,6 +21,7 @@ pub fn probe_lua() {
     #[cfg(feature = "luau")]
     let artifacts = luau0_src::Build::new()
         .enable_codegen(cfg!(feature = "luau-codegen"))
+        .set_max_cstack_size(1000000)
         .set_vector_size(if cfg!(feature = "luau-vector4") { 4 } else { 3 })
         .build();
 

mlua-sys/build/main_inner.rs

@@ -1,3 +1,5 @@
+use std::env;
+
 cfg_if::cfg_if! {
     if #[cfg(any(feature = "luau", feature = "vendored"))] {
         #[path = "find_vendored.rs"]
@@ -17,8 +19,8 @@ fn main() {
 
     println!("cargo:rerun-if-changed=build");
 
-    #[cfg(windows)]
-    if cfg!(feature = "module") {
+    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();

mlua-sys/src/lib.rs

@@ -39,20 +39,22 @@ pub const LUA_MAX_UPVALUES: c_int = 200;
 #[doc(hidden)]
 pub const LUA_TRACEBACK_STACK: c_int = 11;
 
+// Copied from https://github.com/rust-lang/rust/blob/master/library/std/src/sys/pal/common/alloc.rs
 // The minimum alignment guaranteed by the architecture. This value is used to
 // add fast paths for low alignment values.
-// Copied from https://github.com/rust-lang/rust/blob/master/library/std/src/sys/common/alloc.rs
 #[cfg(any(
     target_arch = "x86",
     target_arch = "arm",
+    target_arch = "m68k",
+    target_arch = "csky",
     target_arch = "mips",
+    target_arch = "mips32r6",
     target_arch = "powerpc",
     target_arch = "powerpc64",
     target_arch = "sparc",
-    target_arch = "asmjs",
     target_arch = "wasm32",
     target_arch = "hexagon",
-    all(target_arch = "riscv32", not(target_os = "espidf")),
+    all(target_arch = "riscv32", not(any(target_os = "espidf", target_os = "zkvm"))),
     all(target_arch = "xtensa", not(target_os = "espidf")),
 ))]
 #[doc(hidden)]
@@ -60,18 +62,20 @@ pub const SYS_MIN_ALIGN: usize = 8;
 #[cfg(any(
     target_arch = "x86_64",
     target_arch = "aarch64",
+    target_arch = "arm64ec",
+    target_arch = "loongarch64",
     target_arch = "mips64",
+    target_arch = "mips64r6",
     target_arch = "s390x",
     target_arch = "sparc64",
     target_arch = "riscv64",
     target_arch = "wasm64",
-    target_arch = "loongarch64",
 ))]
 #[doc(hidden)]
 pub const SYS_MIN_ALIGN: usize = 16;
-// The allocator on the esp-idf platform guarentees 4 byte alignment.
+// The allocator on the esp-idf and zkvm platforms guarantee 4 byte alignment.
 #[cfg(any(
-    all(target_arch = "riscv32", target_os = "espidf"),
+    all(target_arch = "riscv32", any(target_os = "espidf", target_os = "zkvm")),
     all(target_arch = "xtensa", target_os = "espidf"),
 ))]
 #[doc(hidden)]

mlua-sys/src/lua51/compat.rs

@@ -2,10 +2,8 @@
 //!
 //! Based on github.com/keplerproject/lua-compat-5.3
 
-use std::convert::TryInto;
-use std::mem;
 use std::os::raw::{c_char, c_int, c_void};
-use std::ptr;
+use std::{mem, ptr};
 
 use super::lauxlib::*;
 use super::lua::*;
@@ -329,12 +327,7 @@ pub unsafe fn lua_setuservalue(L: *mut lua_State, idx: c_int) {
 }
 
 #[inline(always)]
-pub unsafe fn lua_dump(
-    L: *mut lua_State,
-    writer: lua_Writer,
-    data: *mut c_void,
-    _strip: c_int,
-) -> c_int {
+pub unsafe fn lua_dump(L: *mut lua_State, writer: lua_Writer, data: *mut c_void, _strip: c_int) -> c_int {
     lua_dump_(L, writer, data)
 }
 
@@ -366,12 +359,7 @@ pub unsafe fn lua_pushglobaltable(L: *mut lua_State) {
 }
 
 #[inline(always)]
-pub unsafe fn lua_resume(
-    L: *mut lua_State,
-    _from: *mut lua_State,
-    narg: c_int,
-    nres: *mut c_int,
-) -> c_int {
+pub unsafe fn lua_resume(L: *mut lua_State, _from: *mut lua_State, narg: c_int, nres: *mut c_int) -> c_int {
     let ret = lua_resume_(L, narg);
     if (ret == LUA_OK || ret == LUA_YIELD) && !(nres.is_null()) {
         *nres = lua_gettop(L);
@@ -415,6 +403,25 @@ pub unsafe fn luaL_newmetatable(L: *mut lua_State, tname: *const c_char) -> c_in
     }
 }
 
+pub unsafe fn luaL_loadbufferenv(
+    L: *mut lua_State,
+    data: *const c_char,
+    size: usize,
+    name: *const c_char,
+    mode: *const c_char,
+    mut env: c_int,
+) -> c_int {
+    if env != 0 {
+        env = lua_absindex(L, env);
+    }
+    let status = luaL_loadbufferx(L, data, size, name, mode);
+    if status == LUA_OK && env != 0 {
+        lua_pushvalue(L, env);
+        lua_setfenv(L, -2);
+    }
+    status
+}
+
 #[inline(always)]
 pub unsafe fn luaL_loadbufferx(
     L: *mut lua_State,
@@ -447,12 +454,7 @@ pub unsafe fn luaL_len(L: *mut lua_State, idx: c_int) -> lua_Integer {
     res
 }
 
-pub unsafe fn luaL_traceback(
-    L: *mut lua_State,
-    L1: *mut lua_State,
-    msg: *const c_char,
-    mut level: c_int,
-) {
+pub unsafe fn luaL_traceback(L: *mut lua_State, L1: *mut lua_State, msg: *const c_char, mut level: c_int) {
     let mut ar: lua_Debug = mem::zeroed();
     let top = lua_gettop(L);
     let numlevels = compat53_countlevels(L1);
@@ -544,12 +546,7 @@ pub unsafe fn luaL_getsubtable(L: *mut lua_State, idx: c_int, fname: *const c_ch
     0
 }
 
-pub unsafe fn luaL_requiref(
-    L: *mut lua_State,
-    modname: *const c_char,
-    openf: lua_CFunction,
-    glb: c_int,
-) {
+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"));
     if lua_getfield(L, -1, modname) == LUA_TNIL {

mlua-sys/src/lua51/lauxlib.rs

@@ -63,12 +63,7 @@ extern "C-unwind" {
     pub fn luaL_unref(L: *mut lua_State, t: c_int, r#ref: c_int);
 
     pub fn luaL_loadfile(L: *mut lua_State, filename: *const c_char) -> c_int;
-    pub fn luaL_loadbuffer(
-        L: *mut lua_State,
-        buff: *const c_char,
-        sz: usize,
-        name: *const c_char,
-    ) -> c_int;
+    pub fn luaL_loadbuffer(L: *mut lua_State, buff: *const c_char, sz: usize, name: *const c_char) -> c_int;
     pub fn luaL_loadstring(L: *mut lua_State, s: *const c_char) -> c_int;
 
     pub fn luaL_newstate() -> *mut lua_State;

mlua-sys/src/lua51/lua.rs

@@ -328,6 +328,14 @@ pub unsafe fn lua_getglobal_(L: *mut lua_State, var: *const c_char) {
     lua_getfield_(L, LUA_GLOBALSINDEX, var)
 }
 
+#[inline(always)]
+pub unsafe fn lua_tolightuserdata(L: *mut lua_State, idx: c_int) -> *mut c_void {
+    if lua_islightuserdata(L, idx) != 0 {
+        return lua_touserdata(L, idx);
+    }
+    ptr::null_mut()
+}
+
 #[inline(always)]
 pub unsafe fn lua_tostring(L: *mut lua_State, i: c_int) -> *const c_char {
     lua_tolstring(L, i, ptr::null_mut())
@@ -371,12 +379,7 @@ extern "C-unwind" {
     pub fn lua_getupvalue(L: *mut lua_State, funcindex: c_int, n: c_int) -> *const c_char;
     pub fn lua_setupvalue(L: *mut lua_State, funcindex: c_int, n: c_int) -> *const c_char;
 
-    pub fn lua_sethook(
-        L: *mut lua_State,
-        func: Option<lua_Hook>,
-        mask: c_int,
-        count: c_int,
-    ) -> c_int;
+    pub fn lua_sethook(L: *mut lua_State, func: Option<lua_Hook>, mask: c_int, count: c_int) -> c_int;
     pub fn lua_gethook(L: *mut lua_State) -> Option<lua_Hook>;
     pub fn lua_gethookmask(L: *mut lua_State) -> c_int;
     pub fn lua_gethookcount(L: *mut lua_State) -> c_int;

mlua-sys/src/lua52/compat.rs

@@ -2,7 +2,6 @@
 //!
 //! Based on github.com/keplerproject/lua-compat-5.3
 
-use std::convert::TryInto;
 use std::os::raw::{c_char, c_int, c_void};
 use std::ptr;
 
@@ -158,22 +157,12 @@ pub unsafe fn lua_rawseti(L: *mut lua_State, idx: c_int, n: lua_Integer) {
 }
 
 #[inline(always)]
-pub unsafe fn lua_dump(
-    L: *mut lua_State,
-    writer: lua_Writer,
-    data: *mut c_void,
-    _strip: c_int,
-) -> c_int {
+pub unsafe fn lua_dump(L: *mut lua_State, writer: lua_Writer, data: *mut c_void, _strip: c_int) -> c_int {
     lua_dump_(L, writer, data)
 }
 
 #[inline(always)]
-pub unsafe fn lua_resume(
-    L: *mut lua_State,
-    from: *mut lua_State,
-    narg: c_int,
-    nres: *mut c_int,
-) -> c_int {
+pub unsafe fn lua_resume(L: *mut lua_State, from: *mut lua_State, narg: c_int, nres: *mut c_int) -> c_int {
     let ret = lua_resume_(L, from, narg);
     if (ret == LUA_OK || ret == LUA_YIELD) && !(nres.is_null()) {
         *nres = lua_gettop(L);
@@ -241,12 +230,7 @@ pub unsafe fn luaL_tolstring(L: *mut lua_State, mut idx: c_int, len: *mut usize)
     lua_tolstring(L, -1, len)
 }
 
-pub unsafe fn luaL_requiref(
-    L: *mut lua_State,
-    modname: *const c_char,
-    openf: lua_CFunction,
-    glb: c_int,
-) {
+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"));
     if lua_getfield(L, -1, modname) == LUA_TNIL {
@@ -263,3 +247,22 @@ pub unsafe fn luaL_requiref(
     }
     lua_replace(L, -2);
 }
+
+pub unsafe fn luaL_loadbufferenv(
+    L: *mut lua_State,
+    data: *const c_char,
+    size: usize,
+    name: *const c_char,
+    mode: *const c_char,
+    mut env: c_int,
+) -> c_int {
+    if env != 0 {
+        env = lua_absindex(L, env);
+    }
+    let status = luaL_loadbufferx(L, data, size, name, mode);
+    if status == LUA_OK && env != 0 {
+        lua_pushvalue(L, env);
+        lua_setupvalue(L, -2, 1);
+    }
+    status
+}

mlua-sys/src/lua52/lauxlib.rs

@@ -25,12 +25,8 @@ extern "C-unwind" {
     pub fn luaL_tolstring_(L: *mut lua_State, idx: c_int, len: *mut usize) -> *const c_char;
     pub fn luaL_argerror(L: *mut lua_State, arg: c_int, extramsg: *const c_char) -> c_int;
     pub fn luaL_checklstring(L: *mut lua_State, arg: c_int, l: *mut usize) -> *const c_char;
-    pub fn luaL_optlstring(
-        L: *mut lua_State,
-        arg: c_int,
-        def: *const c_char,
-        l: *mut usize,
-    ) -> *const c_char;
+    pub fn luaL_optlstring(L: *mut lua_State, arg: c_int, def: *const c_char, l: *mut usize)
+        -> *const c_char;
     pub fn luaL_checknumber(L: *mut lua_State, arg: c_int) -> lua_Number;
     pub fn luaL_optnumber(L: *mut lua_State, arg: c_int, def: lua_Number) -> lua_Number;
     pub fn luaL_checkinteger(L: *mut lua_State, arg: c_int) -> lua_Integer;
@@ -71,8 +67,7 @@ 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);
 
-    pub fn luaL_loadfilex(L: *mut lua_State, filename: *const c_char, mode: *const c_char)
-        -> c_int;
+    pub fn luaL_loadfilex(L: *mut lua_State, filename: *const c_char, mode: *const c_char) -> c_int;
 }
 
 #[inline(always)]
@@ -109,12 +104,7 @@ extern "C-unwind" {
     pub fn luaL_traceback(L: *mut lua_State, L1: *mut lua_State, msg: *const c_char, level: c_int);
 
     #[link_name = "luaL_requiref"]
-    pub fn luaL_requiref_(
-        L: *mut lua_State,
-        modname: *const c_char,
-        openf: lua_CFunction,
-        glb: c_int,
-    );
+    pub fn luaL_requiref_(L: *mut lua_State, modname: *const c_char, openf: lua_CFunction, glb: c_int);
 }
 
 //
@@ -173,12 +163,7 @@ pub unsafe fn luaL_getmetatable(L: *mut lua_State, n: *const c_char) {
 // luaL_opt would be implemented here but it is undocumented, so it's omitted
 
 #[inline(always)]
-pub unsafe fn luaL_loadbuffer(
-    L: *mut lua_State,
-    s: *const c_char,
-    sz: usize,
-    n: *const c_char,
-) -> c_int {
+pub unsafe fn luaL_loadbuffer(L: *mut lua_State, s: *const c_char, sz: usize, n: *const c_char) -> c_int {
     luaL_loadbufferx(L, s, sz, n, ptr::null())
 }
 

mlua-sys/src/lua52/lua.rs

@@ -222,13 +222,7 @@ extern "C-unwind" {
     //
     // 'load' and 'call' functions (load and run Lua code)
     //
-    pub fn lua_callk(
-        L: *mut lua_State,
-        nargs: c_int,
-        nresults: c_int,
-        ctx: c_int,
-        k: Option<lua_CFunction>,
-    );
+    pub fn lua_callk(L: *mut lua_State, nargs: c_int, nresults: c_int, ctx: c_int, k: Option<lua_CFunction>);
     pub fn lua_pcallk(
         L: *mut lua_State,
         nargs: c_int,
@@ -266,12 +260,7 @@ extern "C-unwind" {
     //
     // Coroutine functions
     //
-    pub fn lua_yieldk(
-        L: *mut lua_State,
-        nresults: c_int,
-        ctx: c_int,
-        k: Option<lua_CFunction>,
-    ) -> c_int;
+    pub fn lua_yieldk(L: *mut lua_State, nresults: c_int, ctx: c_int, k: Option<lua_CFunction>) -> c_int;
     #[link_name = "lua_resume"]
     pub fn lua_resume_(L: *mut lua_State, from: *mut lua_State, narg: c_int) -> c_int;
     pub fn lua_status(L: *mut lua_State) -> c_int;
@@ -417,6 +406,14 @@ pub unsafe fn lua_pushglobaltable(L: *mut lua_State) {
     lua_rawgeti_(L, LUA_REGISTRYINDEX, LUA_RIDX_GLOBALS as _)
 }
 
+#[inline(always)]
+pub unsafe fn lua_tolightuserdata(L: *mut lua_State, idx: c_int) -> *mut c_void {
+    if lua_islightuserdata(L, idx) != 0 {
+        return lua_touserdata(L, idx);
+    }
+    ptr::null_mut()
+}
+
 #[inline(always)]
 pub unsafe fn lua_tostring(L: *mut lua_State, i: c_int) -> *const c_char {
     lua_tolstring(L, i, ptr::null_mut())
@@ -463,12 +460,7 @@ extern "C-unwind" {
     pub fn lua_upvalueid(L: *mut lua_State, fidx: c_int, n: c_int) -> *mut c_void;
     pub fn lua_upvaluejoin(L: *mut lua_State, fidx1: c_int, n1: c_int, fidx2: c_int, n2: c_int);
 
-    pub fn lua_sethook(
-        L: *mut lua_State,
-        func: Option<lua_Hook>,
-        mask: c_int,
-        count: c_int,
-    ) -> c_int;
+    pub fn lua_sethook(L: *mut lua_State, func: Option<lua_Hook>, mask: c_int, count: c_int) -> c_int;
     pub fn lua_gethook(L: *mut lua_State) -> Option<lua_Hook>;
     pub fn lua_gethookmask(L: *mut lua_State) -> c_int;
     pub fn lua_gethookcount(L: *mut lua_State) -> c_int;

mlua-sys/src/lua53/compat.rs

@@ -1,19 +1,34 @@
 //! MLua compatibility layer for Lua 5.3
 
-use std::os::raw::c_int;
+use std::os::raw::{c_char, c_int};
 
+use super::lauxlib::*;
 use super::lua::*;
 
 #[inline(always)]
-pub unsafe fn lua_resume(
-    L: *mut lua_State,
-    from: *mut lua_State,
-    narg: c_int,
-    nres: *mut c_int,
-) -> c_int {
+pub unsafe fn lua_resume(L: *mut lua_State, from: *mut lua_State, narg: c_int, nres: *mut c_int) -> c_int {
     let ret = lua_resume_(L, from, narg);
     if (ret == LUA_OK || ret == LUA_YIELD) && !(nres.is_null()) {
         *nres = lua_gettop(L);
     }
     ret
 }
+
+pub unsafe fn luaL_loadbufferenv(
+    L: *mut lua_State,
+    data: *const c_char,
+    size: usize,
+    name: *const c_char,
+    mode: *const c_char,
+    mut env: c_int,
+) -> c_int {
+    if env != 0 {
+        env = lua_absindex(L, env);
+    }
+    let status = luaL_loadbufferx(L, data, size, name, mode);
+    if status == LUA_OK && env != 0 {
+        lua_pushvalue(L, env);
+        lua_setupvalue(L, -2, 1);
+    }
+    status
+}

mlua-sys/src/lua53/lauxlib.rs

@@ -30,12 +30,8 @@ extern "C-unwind" {
     pub fn luaL_tolstring_(L: *mut lua_State, idx: c_int, len: *mut usize) -> *const c_char;
     pub fn luaL_argerror(L: *mut lua_State, arg: c_int, extramsg: *const c_char) -> c_int;
     pub fn luaL_checklstring(L: *mut lua_State, arg: c_int, l: *mut usize) -> *const c_char;
-    pub fn luaL_optlstring(
-        L: *mut lua_State,
-        arg: c_int,
-        def: *const c_char,
-        l: *mut usize,
-    ) -> *const c_char;
+    pub fn luaL_optlstring(L: *mut lua_State, arg: c_int, def: *const c_char, l: *mut usize)
+        -> *const c_char;
     pub fn luaL_checknumber(L: *mut lua_State, arg: c_int) -> lua_Number;
     pub fn luaL_optnumber(L: *mut lua_State, arg: c_int, def: lua_Number) -> lua_Number;
     pub fn luaL_checkinteger(L: *mut lua_State, arg: c_int) -> lua_Integer;
@@ -73,8 +69,7 @@ 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);
 
-    pub fn luaL_loadfilex(L: *mut lua_State, filename: *const c_char, mode: *const c_char)
-        -> c_int;
+    pub fn luaL_loadfilex(L: *mut lua_State, filename: *const c_char, mode: *const c_char) -> c_int;
 }
 
 #[inline(always)]
@@ -110,12 +105,7 @@ extern "C-unwind" {
 
     pub fn luaL_traceback(L: *mut lua_State, L1: *mut lua_State, msg: *const c_char, level: c_int);
 
-    pub fn luaL_requiref(
-        L: *mut lua_State,
-        modname: *const c_char,
-        openf: lua_CFunction,
-        glb: c_int,
-    );
+    pub fn luaL_requiref(L: *mut lua_State, modname: *const c_char, openf: lua_CFunction, glb: c_int);
 }
 
 //
@@ -179,12 +169,7 @@ pub unsafe fn luaL_tolstring(L: *mut lua_State, idx: c_int, len: *mut usize) ->
 // luaL_opt would be implemented here but it is undocumented, so it's omitted
 
 #[inline(always)]
-pub unsafe fn luaL_loadbuffer(
-    L: *mut lua_State,
-    s: *const c_char,
-    sz: usize,
-    n: *const c_char,
-) -> c_int {
+pub unsafe fn luaL_loadbuffer(L: *mut lua_State, s: *const c_char, sz: usize, n: *const c_char) -> c_int {
     luaL_loadbufferx(L, s, sz, n, ptr::null())
 }
 

mlua-sys/src/lua53/lua.rs

@@ -1,9 +1,8 @@
 //! Contains definitions from `lua.h`.
 
 use std::marker::{PhantomData, PhantomPinned};
-use std::mem;
 use std::os::raw::{c_char, c_double, c_int, c_uchar, c_void};
-use std::ptr;
+use std::{mem, ptr};
 
 // Mark for precompiled code (`<esc>Lua`)
 pub const LUA_SIGNATURE: &[u8] = b"\x1bLua";
@@ -251,12 +250,7 @@ extern "C-unwind" {
         mode: *const c_char,
     ) -> c_int;
 
-    pub fn lua_dump(
-        L: *mut lua_State,
-        writer: lua_Writer,
-        data: *mut c_void,
-        strip: c_int,
-    ) -> c_int;
+    pub fn lua_dump(L: *mut lua_State, writer: lua_Writer, data: *mut c_void, strip: c_int) -> c_int;
 }
 
 #[inline(always)]
@@ -424,6 +418,14 @@ pub unsafe fn lua_pushglobaltable(L: *mut lua_State) -> c_int {
     lua_rawgeti(L, LUA_REGISTRYINDEX, LUA_RIDX_GLOBALS)
 }
 
+#[inline(always)]
+pub unsafe fn lua_tolightuserdata(L: *mut lua_State, idx: c_int) -> *mut c_void {
+    if lua_islightuserdata(L, idx) != 0 {
+        return lua_touserdata(L, idx);
+    }
+    ptr::null_mut()
+}
+
 #[inline(always)]
 pub unsafe fn lua_tostring(L: *mut lua_State, i: c_int) -> *const c_char {
     lua_tolstring(L, i, ptr::null_mut())

mlua-sys/src/lua54/lauxlib.rs

@@ -29,12 +29,8 @@ extern "C-unwind" {
     pub fn luaL_tolstring(L: *mut lua_State, idx: c_int, len: *mut usize) -> *const c_char;
     pub fn luaL_argerror(L: *mut lua_State, arg: c_int, extramsg: *const c_char) -> c_int;
     pub fn luaL_checklstring(L: *mut lua_State, arg: c_int, l: *mut usize) -> *const c_char;
-    pub fn luaL_optlstring(
-        L: *mut lua_State,
-        arg: c_int,
-        def: *const c_char,
-        l: *mut usize,
-    ) -> *const c_char;
+    pub fn luaL_optlstring(L: *mut lua_State, arg: c_int, def: *const c_char, l: *mut usize)
+        -> *const c_char;
     pub fn luaL_checknumber(L: *mut lua_State, arg: c_int) -> lua_Number;
     pub fn luaL_optnumber(L: *mut lua_State, arg: c_int, def: lua_Number) -> lua_Number;
     pub fn luaL_checkinteger(L: *mut lua_State, arg: c_int) -> lua_Integer;
@@ -72,8 +68,7 @@ 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);
 
-    pub fn luaL_loadfilex(L: *mut lua_State, filename: *const c_char, mode: *const c_char)
-        -> c_int;
+    pub fn luaL_loadfilex(L: *mut lua_State, filename: *const c_char, mode: *const c_char) -> c_int;
 }
 
 #[inline(always)]
@@ -111,12 +106,7 @@ extern "C-unwind" {
 
     pub fn luaL_traceback(L: *mut lua_State, L1: *mut lua_State, msg: *const c_char, level: c_int);
 
-    pub fn luaL_requiref(
-        L: *mut lua_State,
-        modname: *const c_char,
-        openf: lua_CFunction,
-        glb: c_int,
-    );
+    pub fn luaL_requiref(L: *mut lua_State, modname: *const c_char, openf: lua_CFunction, glb: c_int);
 }
 
 //
@@ -175,15 +165,29 @@ pub unsafe fn luaL_getmetatable(L: *mut lua_State, n: *const c_char) {
 // luaL_opt would be implemented here but it is undocumented, so it's omitted
 
 #[inline(always)]
-pub unsafe fn luaL_loadbuffer(
-    L: *mut lua_State,
-    s: *const c_char,
-    sz: usize,
-    n: *const c_char,
-) -> c_int {
+pub unsafe fn luaL_loadbuffer(L: *mut lua_State, s: *const c_char, sz: usize, n: *const c_char) -> c_int {
     luaL_loadbufferx(L, s, sz, n, ptr::null())
 }
 
+pub unsafe fn luaL_loadbufferenv(
+    L: *mut lua_State,
+    data: *const c_char,
+    size: usize,
+    name: *const c_char,
+    mode: *const c_char,
+    mut env: c_int,
+) -> c_int {
+    if env != 0 {
+        env = lua::lua_absindex(L, env);
+    }
+    let status = luaL_loadbufferx(L, data, size, name, mode);
+    if status == lua::LUA_OK && env != 0 {
+        lua::lua_pushvalue(L, env);
+        lua::lua_setupvalue(L, -2, 1);
+    }
+    status
+}
+
 //
 // TODO: Generic Buffer Manipulation
 //

mlua-sys/src/lua54/lua.rs

@@ -1,9 +1,8 @@
 //! Contains definitions from `lua.h`.
 
 use std::marker::{PhantomData, PhantomPinned};
-use std::mem;
 use std::os::raw::{c_char, c_double, c_int, c_uchar, c_ushort, c_void};
-use std::ptr;
+use std::{mem, ptr};
 
 // Mark for precompiled code (`<esc>Lua`)
 pub const LUA_SIGNATURE: &[u8] = b"\x1bLua";
@@ -101,8 +100,7 @@ pub type lua_Alloc =
     unsafe extern "C-unwind" 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);
+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" {
@@ -266,12 +264,7 @@ extern "C-unwind" {
         mode: *const c_char,
     ) -> c_int;
 
-    pub fn lua_dump(
-        L: *mut lua_State,
-        writer: lua_Writer,
-        data: *mut c_void,
-        strip: c_int,
-    ) -> c_int;
+    pub fn lua_dump(L: *mut lua_State, writer: lua_Writer, data: *mut c_void, strip: c_int) -> c_int;
 }
 
 #[inline(always)]
@@ -295,12 +288,7 @@ extern "C-unwind" {
         ctx: lua_KContext,
         k: Option<lua_KFunction>,
     ) -> c_int;
-    pub fn lua_resume(
-        L: *mut lua_State,
-        from: *mut lua_State,
-        narg: c_int,
-        nres: *mut c_int,
-    ) -> c_int;
+    pub fn lua_resume(L: *mut lua_State, from: *mut lua_State, narg: c_int, nres: *mut c_int) -> c_int;
     pub fn lua_status(L: *mut lua_State) -> c_int;
     pub fn lua_isyieldable(L: *mut lua_State) -> c_int;
 }
@@ -457,6 +445,14 @@ pub unsafe fn lua_pushglobaltable(L: *mut lua_State) -> c_int {
     lua_rawgeti(L, LUA_REGISTRYINDEX, LUA_RIDX_GLOBALS)
 }
 
+#[inline(always)]
+pub unsafe fn lua_tolightuserdata(L: *mut lua_State, idx: c_int) -> *mut c_void {
+    if lua_islightuserdata(L, idx) != 0 {
+        return lua_touserdata(L, idx);
+    }
+    ptr::null_mut()
+}
+
 #[inline(always)]
 pub unsafe fn lua_tostring(L: *mut lua_State, i: c_int) -> *const c_char {
     lua_tolstring(L, i, ptr::null_mut())

mlua-sys/src/luau/compat.rs

@@ -3,9 +3,8 @@
 //! Based on github.com/keplerproject/lua-compat-5.3
 
 use std::ffi::CStr;
-use std::mem;
 use std::os::raw::{c_char, c_int, c_void};
-use std::ptr;
+use std::{mem, ptr};
 
 use super::lauxlib::*;
 use super::lua::*;
@@ -53,11 +52,7 @@ unsafe fn compat53_findfield(L: *mut lua_State, objidx: c_int, level: c_int) ->
     0 // not found
 }
 
-unsafe fn compat53_pushglobalfuncname(
-    L: *mut lua_State,
-    level: c_int,
-    ar: *mut lua_Debug,
-) -> c_int {
+unsafe fn compat53_pushglobalfuncname(L: *mut lua_State, level: c_int, ar: *mut lua_Debug) -> c_int {
     let top = lua_gettop(L);
     // push function
     lua_getinfo(L, level, cstr!("f"), ar);
@@ -281,12 +276,7 @@ pub unsafe fn lua_pushglobaltable(L: *mut lua_State) {
 }
 
 #[inline(always)]
-pub unsafe fn lua_resume(
-    L: *mut lua_State,
-    from: *mut lua_State,
-    narg: c_int,
-    nres: *mut c_int,
-) -> c_int {
+pub unsafe fn lua_resume(L: *mut lua_State, from: *mut lua_State, narg: c_int, nres: *mut c_int) -> c_int {
     let ret = lua_resume_(L, from, narg);
     if (ret == LUA_OK || ret == LUA_YIELD) && !(nres.is_null()) {
         *nres = lua_gettop(L);
@@ -330,12 +320,13 @@ pub unsafe fn luaL_newmetatable(L: *mut lua_State, tname: *const c_char) -> c_in
     }
 }
 
-pub unsafe fn luaL_loadbufferx(
+pub unsafe fn luaL_loadbufferenv(
     L: *mut lua_State,
     data: *const c_char,
     mut size: usize,
     name: *const c_char,
     mode: *const c_char,
+    env: c_int,
 ) -> c_int {
     extern "C" {
         fn free(p: *mut c_void);
@@ -345,35 +336,38 @@ pub unsafe fn luaL_loadbufferx(
     if !mode.is_null() {
         let modeb = CStr::from_ptr(mode).to_bytes();
         if !chunk_is_text && !modeb.contains(&b'b') {
-            lua_pushfstring(
-                L,
-                cstr!("attempt to load a binary chunk (mode is '%s')"),
-                mode,
-            );
+            lua_pushfstring(L, cstr!("attempt to load a binary chunk (mode is '%s')"), mode);
             return LUA_ERRSYNTAX;
         } else if chunk_is_text && !modeb.contains(&b't') {
-            lua_pushfstring(
-                L,
-                cstr!("attempt to load a text chunk (mode is '%s')"),
-                mode,
-            );
+            lua_pushfstring(L, cstr!("attempt to load a text chunk (mode is '%s')"), mode);
             return LUA_ERRSYNTAX;
         }
     }
 
     if chunk_is_text {
         let data = luau_compile_(data, size, ptr::null_mut(), &mut size);
-        let ok = luau_load(L, name, data, size, 0) == 0;
+        let ok = luau_load(L, name, data, size, env) == 0;
         free(data as *mut c_void);
         if !ok {
             return LUA_ERRSYNTAX;
         }
-    } else if luau_load(L, name, data, size, 0) != 0 {
+    } else if luau_load(L, name, data, size, env) != 0 {
         return LUA_ERRSYNTAX;
     }
     LUA_OK
 }
 
+#[inline(always)]
+pub unsafe fn luaL_loadbufferx(
+    L: *mut lua_State,
+    data: *const c_char,
+    size: usize,
+    name: *const c_char,
+    mode: *const c_char,
+) -> c_int {
+    luaL_loadbufferenv(L, data, size, name, mode, 0)
+}
+
 #[inline(always)]
 pub unsafe fn luaL_loadbuffer(
     L: *mut lua_State,
@@ -381,7 +375,7 @@ pub unsafe fn luaL_loadbuffer(
     size: usize,
     name: *const c_char,
 ) -> c_int {
-    luaL_loadbufferx(L, data, size, name, ptr::null())
+    luaL_loadbufferenv(L, data, size, name, ptr::null(), 0)
 }
 
 #[inline(always)]
@@ -397,12 +391,7 @@ pub unsafe fn luaL_len(L: *mut lua_State, idx: c_int) -> lua_Integer {
     res
 }
 
-pub unsafe fn luaL_traceback(
-    L: *mut lua_State,
-    L1: *mut lua_State,
-    msg: *const c_char,
-    mut level: c_int,
-) {
+pub unsafe fn luaL_traceback(L: *mut lua_State, L1: *mut lua_State, msg: *const c_char, mut level: c_int) {
     let mut ar: lua_Debug = mem::zeroed();
     let top = lua_gettop(L);
     let numlevels = lua_stackdepth(L);
@@ -494,12 +483,7 @@ pub unsafe fn luaL_getsubtable(L: *mut lua_State, idx: c_int, fname: *const c_ch
     0
 }
 
-pub unsafe fn luaL_requiref(
-    L: *mut lua_State,
-    modname: *const c_char,
-    openf: lua_CFunction,
-    glb: c_int,
-) {
+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"));
     if lua_getfield(L, -1, modname) == LUA_TNIL {

mlua-sys/src/luau/lauxlib.rs

@@ -3,9 +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_Integer, lua_Number, lua_State, lua_Unsigned, LUA_REGISTRYINDEX};
 
 #[repr(C)]
 pub struct luaL_Reg {
@@ -144,9 +142,12 @@ pub unsafe fn luaL_sandbox(L: *mut lua_State, enabled: c_int) {
 
     // set all builtin metatables to read-only
     lua_pushliteral(L, "");
-    lua_getmetatable(L, -1);
-    lua_setreadonly(L, -1, enabled);
-    lua_pop(L, 2);
+    if lua_getmetatable(L, -1) != 0 {
+        lua_setreadonly(L, -1, enabled);
+        lua_pop(L, 2);
+    } else {
+        lua_pop(L, 1);
+    }
 
     // set globals to readonly and activate safeenv since the env is immutable
     lua_setreadonly(L, LUA_GLOBALSINDEX, enabled);

mlua-sys/src/luau/lua.rs

@@ -8,7 +8,13 @@ use std::{mem, ptr};
 pub const LUA_MULTRET: c_int = -1;
 
 // Max number of Lua stack slots
-const LUAI_MAXCSTACK: c_int = 100000;
+const LUAI_MAXCSTACK: c_int = 1000000;
+
+// Number of valid Lua userdata tags
+const LUA_UTAG_LIMIT: c_int = 128;
+
+// Number of valid Lua lightuserdata tags
+const LUA_LUTAG_LIMIT: c_int = 128;
 
 //
 // Pseudo-indices
@@ -78,12 +84,8 @@ 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 memory-allocation functions.
-pub type lua_Alloc = unsafe extern "C-unwind" fn(
-    ud: *mut c_void,
-    ptr: *mut c_void,
-    osize: usize,
-    nsize: usize,
-) -> *mut c_void;
+pub type lua_Alloc =
+    unsafe extern "C-unwind" 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> {
@@ -144,9 +146,11 @@ extern "C-unwind" {
     pub fn lua_objlen(L: *mut lua_State, idx: c_int) -> usize;
     pub fn lua_tocfunction(L: *mut lua_State, idx: c_int) -> Option<lua_CFunction>;
     pub fn lua_tolightuserdata(L: *mut lua_State, idx: c_int) -> *mut c_void;
+    pub fn lua_tolightuserdatatagged(L: *mut lua_State, idx: c_int, tag: c_int) -> *mut c_void;
     pub fn lua_touserdata(L: *mut lua_State, idx: c_int) -> *mut c_void;
     pub fn lua_touserdatatagged(L: *mut lua_State, idx: c_int, tag: c_int) -> *mut c_void;
     pub fn lua_userdatatag(L: *mut lua_State, idx: c_int) -> c_int;
+    pub fn lua_lightuserdatatag(L: *mut lua_State, idx: c_int) -> c_int;
     pub fn lua_tothread(L: *mut lua_State, idx: c_int) -> *mut lua_State;
     pub fn lua_tobuffer(L: *mut lua_State, idx: c_int, len: *mut usize) -> *mut c_void;
     pub fn lua_topointer(L: *mut lua_State, idx: c_int) -> *const c_void;
@@ -179,7 +183,7 @@ extern "C-unwind" {
     pub fn lua_pushboolean(L: *mut lua_State, b: c_int);
     pub fn lua_pushthread(L: *mut lua_State) -> c_int;
 
-    pub fn lua_pushlightuserdata(L: *mut lua_State, p: *mut c_void);
+    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;
 
@@ -280,6 +284,10 @@ 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_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;
     pub fn lua_clonefunction(L: *mut lua_State, idx: c_int);
     pub fn lua_cleartable(L: *mut lua_State, idx: c_int);
     pub fn lua_getallocf(L: *mut lua_State, ud: *mut *mut c_void) -> lua_Alloc;
@@ -398,27 +406,31 @@ pub unsafe fn lua_pushliteral(L: *mut lua_State, s: &'static str) {
     lua_pushlstring_(L, c_str.as_ptr(), c_str.as_bytes().len())
 }
 
+#[inline(always)]
 pub unsafe fn lua_pushcfunction(L: *mut lua_State, f: lua_CFunction) {
     lua_pushcclosurek(L, f, ptr::null(), 0, None)
 }
 
+#[inline(always)]
 pub unsafe fn lua_pushcfunctiond(L: *mut lua_State, f: lua_CFunction, debugname: *const c_char) {
     lua_pushcclosurek(L, f, debugname, 0, None)
 }
 
+#[inline(always)]
 pub unsafe fn lua_pushcclosure(L: *mut lua_State, f: lua_CFunction, nup: c_int) {
     lua_pushcclosurek(L, f, ptr::null(), nup, None)
 }
 
-pub unsafe fn lua_pushcclosured(
-    L: *mut lua_State,
-    f: lua_CFunction,
-    debugname: *const c_char,
-    nup: c_int,
-) {
+#[inline(always)]
+pub unsafe fn lua_pushcclosured(L: *mut lua_State, f: lua_CFunction, debugname: *const c_char, nup: c_int) {
     lua_pushcclosurek(L, f, debugname, nup, None)
 }
 
+#[inline(always)]
+pub unsafe fn lua_pushlightuserdata(L: *mut lua_State, p: *mut c_void) {
+    lua_pushlightuserdatatagged(L, p, 0)
+}
+
 #[inline(always)]
 pub unsafe fn lua_setglobal(L: *mut lua_State, var: *const c_char) {
     lua_setfield(L, LUA_GLOBALSINDEX, var)
@@ -455,12 +467,7 @@ pub type lua_Coverage = unsafe extern "C-unwind" fn(
 
 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_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;
     pub fn lua_getlocal(L: *mut lua_State, level: c_int, n: c_int) -> *const c_char;
     pub fn lua_setlocal(L: *mut lua_State, level: c_int, n: c_int) -> *const c_char;
@@ -468,19 +475,9 @@ extern "C-unwind" {
     pub fn lua_setupvalue(L: *mut lua_State, funcindex: c_int, n: c_int) -> *const c_char;
 
     pub fn lua_singlestep(L: *mut lua_State, enabled: c_int);
-    pub fn lua_breakpoint(
-        L: *mut lua_State,
-        funcindex: c_int,
-        line: c_int,
-        enabled: c_int,
-    ) -> c_int;
+    pub fn lua_breakpoint(L: *mut lua_State, funcindex: c_int, line: c_int, enabled: c_int) -> c_int;
 
-    pub fn lua_getcoverage(
-        L: *mut lua_State,
-        funcindex: c_int,
-        context: *mut c_void,
-        callback: lua_Coverage,
-    );
+    pub fn lua_getcoverage(L: *mut lua_State, funcindex: c_int, context: *mut c_void, callback: lua_Coverage);
 
     pub fn lua_debugtrace(L: *mut lua_State) -> *const c_char;
 }
@@ -506,6 +503,7 @@ pub struct lua_Debug {
 //
 
 #[repr(C)]
+#[non_exhaustive]
 pub struct lua_Callbacks {
     /// arbitrary userdata pointer that is never overwritten by Luau
     pub userdata: *mut c_void,
@@ -533,3 +531,8 @@ pub struct lua_Callbacks {
 extern "C" {
     pub fn lua_callbacks(L: *mut lua_State) -> *mut lua_Callbacks;
 }
+
+// Functions from customization lib
+extern "C" {
+    pub fn luau_setfflag(name: *const c_char, value: c_int) -> c_int;
+}

mlua-sys/src/luau/luacode.rs

@@ -1,17 +1,36 @@
 //! Contains definitions from `luacode.h`.
 
 use std::os::raw::{c_char, c_int, c_void};
-use std::slice;
+use std::{ptr, slice};
 
 #[repr(C)]
+#[non_exhaustive]
 pub struct lua_CompileOptions {
     pub optimizationLevel: c_int,
     pub debugLevel: c_int,
+    pub typeInfoLevel: c_int,
     pub coverageLevel: c_int,
     pub vectorLib: *const c_char,
     pub vectorCtor: *const c_char,
     pub vectorType: *const c_char,
     pub mutableGlobals: *const *const c_char,
+    pub userdataTypes: *const *const c_char,
+}
+
+impl Default for lua_CompileOptions {
+    fn default() -> Self {
+        Self {
+            optimizationLevel: 1,
+            debugLevel: 1,
+            typeInfoLevel: 0,
+            coverageLevel: 0,
+            vectorLib: ptr::null(),
+            vectorCtor: ptr::null(),
+            vectorType: ptr::null(),
+            mutableGlobals: ptr::null(),
+            userdataTypes: ptr::null(),
+        }
+    }
 }
 
 extern "C-unwind" {
@@ -36,6 +55,7 @@ pub unsafe fn luau_compile(source: &[u8], mut options: lua_CompileOptions) -> Ve
         &mut options,
         &mut outsize,
     );
+    assert!(!data_ptr.is_null(), "luau_compile failed");
     let data = slice::from_raw_parts(data_ptr as *mut u8, outsize).to_vec();
     free(data_ptr as *mut c_void);
     data

mlua-sys/src/macros.rs

@@ -1,7 +1,6 @@
 #[allow(unused_macros)]
 macro_rules! cstr {
     ($s:expr) => {
-        concat!($s, "\0") as *const str as *const [::std::os::raw::c_char]
-            as *const ::std::os::raw::c_char
+        concat!($s, "\0") as *const str as *const [::std::os::raw::c_char] as *const ::std::os::raw::c_char
     };
 }

mlua_derive/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mlua_derive"
-version = "0.9.0"
+version = "0.10.0-beta.1"
 authors = ["Aleksandr Orlenko <zxteam@pm.me>"]
 edition = "2021"
 description = "Procedural macros for the mlua crate."
@@ -19,6 +19,6 @@ quote = "1.0"
 proc-macro2 = { version = "1.0", features = ["span-locations"] }
 proc-macro-error = { version = "1.0", optional = true }
 syn = { version = "2.0", features = ["full"] }
-itertools = { version = "0.11", optional = true }
+itertools = { version = "0.13", optional = true }
 regex = { version = "1.4", optional = true }
 once_cell = { version = "1.0", optional = true }

mlua_derive/src/from_lua.rs

@@ -3,20 +3,19 @@ use quote::quote;
 use syn::{parse_macro_input, DeriveInput};
 
 pub fn from_lua(input: TokenStream) -> TokenStream {
-    let DeriveInput {
-        ident, generics, ..
-    } = parse_macro_input!(input as DeriveInput);
+    let DeriveInput { ident, generics, .. } = parse_macro_input!(input as DeriveInput);
 
+    let ident_str = ident.to_string();
+    let (impl_generics, ty_generics, _) = generics.split_for_impl();
     let where_clause = match &generics.where_clause {
         Some(where_clause) => quote! { #where_clause, Self: 'static + Clone },
         None => quote! { where Self: 'static + Clone },
     };
-    let ident_str = ident.to_string();
 
     quote! {
-      impl #generics ::mlua::FromLua<'_> for #ident #generics #where_clause {
+      impl #impl_generics ::mlua::FromLua for #ident #ty_generics #where_clause {
         #[inline]
-        fn from_lua(value: ::mlua::Value<'_>, lua: &'_ ::mlua::Lua) -> ::mlua::Result<Self> {
+        fn from_lua(value: ::mlua::Value, _: &::mlua::Lua) -> ::mlua::Result<Self> {
           match value {
             ::mlua::Value::UserData(ud) => Ok(ud.borrow::<Self>()?.clone()),
             _ => Err(::mlua::Error::FromLuaConversionError {

mlua_derive/src/lib.rs

@@ -51,18 +51,23 @@ pub fn lua_module(attr: TokenStream, item: TokenStream) -> TokenStream {
     let func_name = &func.sig.ident;
     let module_name = args.name.unwrap_or_else(|| func_name.clone());
     let ext_entrypoint_name = Ident::new(&format!("luaopen_{module_name}"), Span::call_site());
-    let skip_memory_check = args.skip_memory_check;
+    let skip_memory_check = if args.skip_memory_check {
+        quote! { lua.skip_memory_check(true); }
+    } else {
+        quote! {}
+    };
 
     let wrapped = quote! {
-        ::mlua::require_module_feature!();
+        mlua::require_module_feature!();
 
         #func
 
         #[no_mangle]
-        unsafe extern "C-unwind" fn #ext_entrypoint_name(state: *mut ::mlua::lua_State) -> ::std::os::raw::c_int {
-            let lua = ::mlua::Lua::init_from_ptr(state);
-            lua.skip_memory_check(#skip_memory_check);
-            lua.entrypoint1(#func_name)
+        unsafe extern "C-unwind" fn #ext_entrypoint_name(state: *mut mlua::lua_State) -> ::std::os::raw::c_int {
+            mlua::Lua::entrypoint1(state, move |lua| {
+                #skip_memory_check
+                #func_name(lua)
+            })
         }
     };
 
@@ -91,19 +96,18 @@ pub fn chunk(input: TokenStream) -> TokenStream {
     });
 
     let wrapped_code = quote! {{
-        use ::mlua::{AsChunk, ChunkMode, Lua, Result, Table};
+        use mlua::{AsChunk, ChunkMode, Lua, Result, Table};
         use ::std::borrow::Cow;
         use ::std::cell::Cell;
         use ::std::io::Result as IoResult;
-        use ::std::marker::PhantomData;
 
-        struct InnerChunk<'lua, F: FnOnce(&'lua Lua) -> Result<Table<'lua>>>(Cell<Option<F>>, PhantomData<&'lua ()>);
+        struct InnerChunk<F: FnOnce(&Lua) -> Result<Table>>(Cell<Option<F>>);
 
-        impl<'lua, F> AsChunk<'lua, 'static> for InnerChunk<'lua, F>
+        impl<F> AsChunk<'static> for InnerChunk<F>
         where
-            F: FnOnce(&'lua Lua) -> Result<Table<'lua>>,
+            F: FnOnce(&Lua) -> Result<Table>,
         {
-            fn environment(&self, lua: &'lua Lua) -> Result<Option<Table<'lua>>> {
+            fn environment(&self, lua: &Lua) -> Result<Option<Table>> {
                 if #caps_len > 0 {
                     if let Some(make_env) = self.0.take() {
                         return make_env(lua).map(Some);
@@ -121,9 +125,7 @@ pub fn chunk(input: TokenStream) -> TokenStream {
             }
         }
 
-        fn annotate<'a, F: FnOnce(&'a Lua) -> Result<Table<'a>>>(f: F) -> F { f }
-
-        let make_env = annotate(move |lua: &Lua| -> Result<Table> {
+        let make_env = move |lua: &Lua| -> Result<Table> {
             let globals = lua.globals();
             let env = lua.create_table()?;
             let meta = lua.create_table()?;
@@ -135,9 +137,9 @@ pub fn chunk(input: TokenStream) -> TokenStream {
 
             env.set_metatable(Some(meta));
             Ok(env)
-        });
+        };
 
-        InnerChunk(Cell::new(Some(make_env)), PhantomData)
+        InnerChunk(Cell::new(Some(make_env)))
     }};
 
     wrapped_code.into()

mlua_derive/src/token.rs

@@ -1,9 +1,6 @@
-use std::{
-    cmp::{Eq, PartialEq},
-    fmt::{self, Display, Formatter},
-    iter::IntoIterator,
-    vec::IntoIter,
-};
+use std::cmp::{Eq, PartialEq};
+use std::fmt::{self, Display, Formatter};
+use std::vec::IntoIter;
 
 use itertools::Itertools;
 use once_cell::sync::Lazy;
@@ -48,10 +45,7 @@ fn span_pos(span: &Span) -> (Pos, Pos) {
         return fallback_span_pos(span);
     }
 
-    (
-        Pos::new(start.line, start.column),
-        Pos::new(end.line, end.column),
-    )
+    (Pos::new(start.line, start.column), Pos::new(end.line, end.column))
 }
 
 fn parse_pos(span: &Span) -> Option<(usize, usize)> {
@@ -80,9 +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_error::abort_call_site!("Cannot retrieve span information; please use nightly"),
     };
     (Pos::new(1, start), Pos::new(1, end))
 }

rustfmt.toml

@@ -0,0 +1,4 @@
+imports_granularity = "Module"
+max_width = 110
+comment_width = 100
+wrap_comments = true

src/chunk.rs

@@ -5,17 +5,17 @@ use std::io::Result as IoResult;
 use std::path::{Path, PathBuf};
 use std::string::String as StdString;
 
-use crate::error::{Error, ErrorContext, Result};
+use crate::error::{Error, Result};
 use crate::function::Function;
-use crate::lua::Lua;
+use crate::state::{Lua, WeakLua};
 use crate::table::Table;
-use crate::value::{FromLuaMulti, IntoLua, IntoLuaMulti};
+use crate::value::{FromLuaMulti, IntoLuaMulti};
 
 /// 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<'lua, 'a> {
+pub trait AsChunk<'a> {
     /// Returns optional chunk name
     fn name(&self) -> Option<StdString> {
         None
@@ -24,7 +24,7 @@ pub trait AsChunk<'lua, 'a> {
     /// Returns optional chunk [environment]
     ///
     /// [environment]: https://www.lua.org/manual/5.4/manual.html#2.2
-    fn environment(&self, lua: &'lua Lua) -> Result<Option<Table<'lua>>> {
+    fn environment(&self, lua: &Lua) -> Result<Option<Table>> {
         let _lua = lua; // suppress warning
         Ok(None)
     }
@@ -38,43 +38,43 @@ pub trait AsChunk<'lua, 'a> {
     fn source(self) -> IoResult<Cow<'a, [u8]>>;
 }
 
-impl<'a> AsChunk<'_, 'a> for &'a str {
+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 {
+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 {
+impl<'a> AsChunk<'a> for &'a StdString {
     fn source(self) -> IoResult<Cow<'a, [u8]>> {
         Ok(Cow::Borrowed(self.as_bytes()))
     }
 }
 
-impl<'a> AsChunk<'_, 'a> for &'a [u8] {
+impl<'a> AsChunk<'a> for &'a [u8] {
     fn source(self) -> IoResult<Cow<'a, [u8]>> {
         Ok(Cow::Borrowed(self))
     }
 }
 
-impl AsChunk<'_, 'static> for Vec<u8> {
+impl AsChunk<'static> for Vec<u8> {
     fn source(self) -> IoResult<Cow<'static, [u8]>> {
         Ok(Cow::Owned(self))
     }
 }
 
-impl<'a> AsChunk<'_, 'a> for &'a Vec<u8> {
+impl<'a> AsChunk<'a> for &'a Vec<u8> {
     fn source(self) -> IoResult<Cow<'a, [u8]>> {
         Ok(Cow::Borrowed(self.as_ref()))
     }
 }
 
-impl AsChunk<'_, 'static> for &Path {
+impl AsChunk<'static> for &Path {
     fn name(&self) -> Option<StdString> {
         Some(format!("@{}", self.display()))
     }
@@ -84,7 +84,7 @@ impl AsChunk<'_, 'static> for &Path {
     }
 }
 
-impl AsChunk<'_, 'static> for PathBuf {
+impl AsChunk<'static> for PathBuf {
     fn name(&self) -> Option<StdString> {
         Some(format!("@{}", self.display()))
     }
@@ -98,10 +98,10 @@ impl AsChunk<'_, 'static> for PathBuf {
 ///
 /// [`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<'lua, 'a> {
-    pub(crate) lua: &'lua Lua,
+pub struct Chunk<'a> {
+    pub(crate) lua: WeakLua,
     pub(crate) name: StdString,
-    pub(crate) env: Result<Option<Table<'lua>>>,
+    pub(crate) env: Result<Option<Table>>,
     pub(crate) mode: Option<ChunkMode>,
     pub(crate) source: IoResult<Cow<'a, [u8]>>,
     #[cfg(feature = "luau")]
@@ -122,17 +122,19 @@ pub enum ChunkMode {
 pub struct Compiler {
     optimization_level: u8,
     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>,
 }
 
 #[cfg(any(feature = "luau", doc))]
 impl Default for Compiler {
     fn default() -> Self {
-        Self::new()
+        const { Self::new() }
     }
 }
 
@@ -144,11 +146,13 @@ impl Compiler {
         Compiler {
             optimization_level: 1,
             debug_level: 1,
+            type_info_level: 0,
             coverage_level: 0,
             vector_lib: None,
             vector_ctor: None,
             vector_type: None,
             mutable_globals: Vec::new(),
+            userdata_types: Vec::new(),
         }
     }
 
@@ -176,6 +180,16 @@ impl Compiler {
         self
     }
 
+    /// Sets Luau type information level used to guide native code generation decisions.
+    ///
+    /// Possible values:
+    /// * 0 - generate for native modules (default)
+    /// * 1 - generate for all modules
+    pub const fn set_type_info_level(mut self, level: u8) -> Self {
+        self.type_info_level = level;
+        self
+    }
+
     /// Sets Luau compiler code coverage level.
     ///
     /// Possible values:
@@ -218,8 +232,17 @@ impl Compiler {
         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;
+        self
+    }
+
     /// Compiles the `source` into bytecode.
-    pub fn compile(&self, source: impl AsRef<[u8]>) -> Vec<u8> {
+    ///
+    /// 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::ptr;
 
@@ -233,38 +256,55 @@ impl Compiler {
         let vector_type = vector_type.and_then(|t| CString::new(t).ok());
         let vector_type = vector_type.as_ref();
 
-        let mutable_globals = self
-            .mutable_globals
-            .iter()
-            .map(|name| CString::new(name.clone()).ok())
-            .collect::<Option<Vec<_>>>()
-            .unwrap_or_default();
-        let mut mutable_globals = mutable_globals
-            .iter()
-            .map(|s| s.as_ptr())
-            .collect::<Vec<_>>();
-        let mut mutable_globals_ptr = ptr::null();
-        if !mutable_globals.is_empty() {
-            mutable_globals.push(ptr::null());
-            mutable_globals_ptr = mutable_globals.as_ptr();
+        macro_rules! vec2cstring_ptr {
+            ($name:ident, $name_ptr:ident) => {
+                let $name = self
+                    .$name
+                    .iter()
+                    .map(|name| CString::new(name.clone()).ok())
+                    .collect::<Option<Vec<_>>>()
+                    .unwrap_or_default();
+                let mut $name = $name.iter().map(|s| s.as_ptr()).collect::<Vec<_>>();
+                let mut $name_ptr = ptr::null();
+                if !$name.is_empty() {
+                    $name.push(ptr::null());
+                    $name_ptr = $name.as_ptr();
+                }
+            };
         }
 
-        unsafe {
-            let options = ffi::lua_CompileOptions {
-                optimizationLevel: self.optimization_level as c_int,
-                debugLevel: self.debug_level as c_int,
-                coverageLevel: self.coverage_level as c_int,
-                vectorLib: vector_lib.map_or(ptr::null(), |s| s.as_ptr()),
-                vectorCtor: vector_ctor.map_or(ptr::null(), |s| s.as_ptr()),
-                vectorType: vector_type.map_or(ptr::null(), |s| s.as_ptr()),
-                mutableGlobals: mutable_globals_ptr,
-            };
+        vec2cstring_ptr!(mutable_globals, mutable_globals_ptr);
+        vec2cstring_ptr!(userdata_types, userdata_types_ptr);
+
+        let bytecode = unsafe {
+            let mut options = ffi::lua_CompileOptions::default();
+            options.optimizationLevel = self.optimization_level as c_int;
+            options.debugLevel = self.debug_level as c_int;
+            options.typeInfoLevel = self.type_info_level as c_int;
+            options.coverageLevel = self.coverage_level as c_int;
+            options.vectorLib = vector_lib.map_or(ptr::null(), |s| s.as_ptr());
+            options.vectorCtor = vector_ctor.map_or(ptr::null(), |s| s.as_ptr());
+            options.vectorType = vector_type.map_or(ptr::null(), |s| s.as_ptr());
+            options.mutableGlobals = mutable_globals_ptr;
+            options.userdataTypes = userdata_types_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();
+            return Err(Error::SyntaxError {
+                incomplete_input: message.ends_with("<eof>"),
+                message,
+            });
         }
+
+        Ok(bytecode)
     }
 }
 
-impl<'lua, 'a> Chunk<'lua, 'a> {
+impl<'a> Chunk<'a> {
     /// Sets the name of this chunk, which results in more informative error traces.
     pub fn set_name(mut self, name: impl Into<String>) -> Self {
         self.name = name.into();
@@ -273,8 +313,8 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
 
     /// 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 `_ENV`
-    /// variable inside the chunk. By default this value is set to the global environment.
+    /// In Lua >=5.2 main chunks always have exactly one upvalue, and this upvalue is used as the
+    /// `_ENV` variable inside the chunk. By default this value is set to the global environment.
     ///
     /// Calling this method changes the `_ENV` upvalue to the value provided, and variables inside
     /// the chunk will refer to the given environment rather than the global one.
@@ -282,11 +322,8 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
     /// All global variables (including the standard library!) are looked up in `_ENV`, so it may be
     /// necessary to populate the environment in order for scripts using custom environments to be
     /// useful.
-    pub fn set_environment<V: IntoLua<'lua>>(mut self, env: V) -> Self {
-        self.env = env
-            .into_lua(self.lua)
-            .and_then(|val| self.lua.unpack(val))
-            .context("bad environment value");
+    pub fn set_environment(mut self, env: Table) -> Self {
+        self.env = Ok(Some(env));
         self
     }
 
@@ -315,8 +352,7 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
     ///
     /// This is equivalent to calling the chunk function with no arguments and no return values.
     pub fn exec(self) -> Result<()> {
-        self.call(())?;
-        Ok(())
+        self.call(())
     }
 
     /// Asynchronously execute this chunk of code.
@@ -337,7 +373,7 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
     /// If the chunk can be parsed as an expression, this loads and executes the chunk and returns
     /// the value that it evaluates to. Otherwise, the chunk is interpreted as a block as normal,
     /// and this is equivalent to calling `exec`.
-    pub fn eval<R: FromLuaMulti<'lua>>(self) -> Result<R> {
+    pub fn eval<R: FromLuaMulti>(self) -> Result<R> {
         // Bytecode is always interpreted as a statement.
         // For source code, first try interpreting the lua as an expression by adding
         // "return", then as a statement. This is the same thing the
@@ -362,7 +398,7 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
     #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
     pub async fn eval_async<R>(self) -> Result<R>
     where
-        R: FromLuaMulti<'lua> + 'lua,
+        R: FromLuaMulti,
     {
         if self.detect_mode() == ChunkMode::Binary {
             self.call_async(()).await
@@ -376,7 +412,7 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
     /// Load the chunk function and call it with the given arguments.
     ///
     /// This is equivalent to `into_function` and calling the resulting function.
-    pub fn call<A: IntoLuaMulti<'lua>, R: FromLuaMulti<'lua>>(self, args: A) -> Result<R> {
+    pub fn call<R: FromLuaMulti>(self, args: impl IntoLuaMulti) -> Result<R> {
         self.into_function()?.call(args)
     }
 
@@ -389,10 +425,9 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
     /// [`call`]: #method.call
     #[cfg(feature = "async")]
     #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
-    pub async fn call_async<A, R>(self, args: A) -> Result<R>
+    pub async fn call_async<R>(self, args: impl IntoLuaMulti) -> Result<R>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua,
+        R: FromLuaMulti,
     {
         self.into_function()?.call_async(args).await
     }
@@ -401,7 +436,7 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
     ///
     /// This simply compiles the chunk without actually executing it.
     #[cfg_attr(not(feature = "luau"), allow(unused_mut))]
-    pub fn into_function(mut self) -> Result<Function<'lua>> {
+    pub fn into_function(mut self) -> Result<Function> {
         #[cfg(feature = "luau")]
         if self.compiler.is_some() {
             // We don't need to compile source if no compiler set
@@ -410,26 +445,23 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
 
         let name = Self::convert_name(self.name)?;
         self.lua
-            .load_chunk(Some(&name), self.env?, self.mode, self.source?.as_ref())
+            .lock()
+            .load_chunk(Some(&name), self.env?.as_ref(), self.mode, self.source?.as_ref())
     }
 
     /// Compiles the chunk and changes mode to binary.
     ///
-    /// It does nothing if the chunk is already binary.
+    /// It does nothing if the chunk is already binary or invalid.
     fn compile(&mut self) {
         if let Ok(ref source) = self.source {
             if self.detect_mode() == ChunkMode::Text {
                 #[cfg(feature = "luau")]
-                {
-                    let data = self
-                        .compiler
-                        .get_or_insert_with(Default::default)
-                        .compile(source);
+                if let Ok(data) = self.compiler.get_or_insert_with(Default::default).compile(source) {
                     self.source = Ok(Cow::Owned(data));
                     self.mode = Some(ChunkMode::Binary);
                 }
                 #[cfg(not(feature = "luau"))]
-                if let Ok(func) = self.lua.load_chunk(None, None, None, source.as_ref()) {
+                if let Ok(func) = self.lua.lock().load_chunk(None, None, None, source.as_ref()) {
                     let data = func.dump(false);
                     self.source = Ok(Cow::Owned(data));
                     self.mode = Some(ChunkMode::Binary);
@@ -448,7 +480,8 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
         let mut text_source = None;
         if let Ok(ref source) = self.source {
             if self.detect_mode() == ChunkMode::Text {
-                if let Some(cache) = self.lua.app_data_ref::<ChunksCache>() {
+                let lua = self.lua.lock();
+                if let Some(cache) = lua.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);
@@ -464,13 +497,14 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
             self.compile();
             if let Ok(ref binary_source) = self.source {
                 if self.detect_mode() == ChunkMode::Binary {
-                    if let Some(mut cache) = self.lua.app_data_mut::<ChunksCache>() {
+                    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());
                     } else {
                         let mut cache = ChunksCache(HashMap::new());
                         cache.0.insert(text_source, binary_source.as_ref().to_vec());
-                        let _ = self.lua.try_set_app_data(cache);
-                    }
+                        let _ = lua.try_set_app_data(cache);
+                    };
                 }
             }
         }
@@ -478,7 +512,7 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
         self
     }
 
-    fn to_expression(&self) -> Result<Function<'lua>> {
+    fn to_expression(&self) -> Result<Function> {
         // We assume that mode is Text
         let source = self.source.as_ref();
         let source = source.map_err(Error::runtime)?;
@@ -489,11 +523,16 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
             .compiler
             .as_ref()
             .map(|c| c.compile(&source))
+            .transpose()?
             .unwrap_or(source);
 
         let name = Self::convert_name(self.name.clone())?;
-        self.lua
-            .load_chunk(Some(&name), self.env.clone()?, None, &source)
+        let env = match &self.env {
+            Ok(Some(env)) => Some(env),
+            Ok(None) => None,
+            Err(err) => return Err(err.clone()),
+        };
+        self.lua.lock().load_chunk(Some(&name), env, None, &source)
     }
 
     fn detect_mode(&self) -> ChunkMode {

src/error.rs

@@ -98,17 +98,17 @@ pub enum Error {
         /// A string containing more detailed error information.
         message: Option<StdString>,
     },
-    /// [`Thread::resume`] was called on an inactive coroutine.
+    /// [`Thread::resume`] was called on an unresumable coroutine.
     ///
-    /// A coroutine is inactive if its main function has returned or if an error has occurred inside
-    /// the coroutine.
+    /// A coroutine is unresumable if its main function has returned or if an error has occurred
+    /// inside the coroutine. Already running coroutines are also marked as unresumable.
     ///
     /// [`Thread::status`] can be used to check if the coroutine can be resumed without causing this
     /// error.
     ///
     /// [`Thread::resume`]: crate::Thread::resume
     /// [`Thread::status`]: crate::Thread::status
-    CoroutineInactive,
+    CoroutineUnresumable,
     /// An [`AnyUserData`] is not the expected type in a borrow.
     ///
     /// This error can only happen when manually using [`AnyUserData`], or when implementing
@@ -259,7 +259,7 @@ impl fmt::Display for Error {
                     Some(ref message) => write!(fmt, " ({message})"),
                 }
             }
-            Error::CoroutineInactive => write!(fmt, "cannot resume inactive coroutine"),
+            Error::CoroutineUnresumable => write!(fmt, "coroutine is non-resumable"),
             Error::UserDataTypeMismatch => write!(fmt, "userdata is not expected type"),
             Error::UserDataDestructed => write!(fmt, "userdata has been destructed"),
             Error::UserDataBorrowError => write!(fmt, "error borrowing userdata"),
@@ -324,7 +324,8 @@ impl StdError for Error {
             // 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.
+            // 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() {

src/function.rs

@@ -1,49 +1,25 @@
 use std::cell::RefCell;
-use std::mem;
 use std::os::raw::{c_int, c_void};
-use std::ptr;
-use std::slice;
+use std::{mem, ptr, slice};
 
 use crate::error::{Error, Result};
-use crate::lua::Lua;
+use crate::state::Lua;
 use crate::table::Table;
-use crate::types::{Callback, LuaRef, MaybeSend};
+use crate::types::{Callback, MaybeSend, ValueRef};
 use crate::util::{
-    assert_stack, check_stack, linenumber_to_usize, pop_error, ptr_to_lossy_str, ptr_to_str,
-    StackGuard,
+    assert_stack, check_stack, linenumber_to_usize, pop_error, ptr_to_lossy_str, ptr_to_str, StackGuard,
 };
 use crate::value::{FromLuaMulti, IntoLua, IntoLuaMulti, Value};
 
 #[cfg(feature = "async")]
 use {
     crate::types::AsyncCallback,
-    futures_util::future::{self, Future},
+    std::future::{self, Future},
 };
 
 /// Handle to an internal Lua function.
 #[derive(Clone, Debug)]
-pub struct Function<'lua>(pub(crate) LuaRef<'lua>);
-
-/// Owned handle to an internal Lua function.
-///
-/// The owned handle holds a *strong* reference to the current Lua instance.
-/// Be warned, if you place it into a Lua type (eg. [`UserData`] or a Rust callback), it is *very easy*
-/// to accidentally cause reference cycles that would prevent destroying Lua instance.
-///
-/// [`UserData`]: crate::UserData
-#[cfg(feature = "unstable")]
-#[cfg_attr(docsrs, doc(cfg(feature = "unstable")))]
-#[derive(Clone, Debug)]
-pub struct OwnedFunction(pub(crate) crate::types::LuaOwnedRef);
-
-#[cfg(feature = "unstable")]
-impl OwnedFunction {
-    /// Get borrowed handle to the underlying Lua function.
-    #[cfg_attr(feature = "send", allow(unused))]
-    pub const fn to_ref(&self) -> Function {
-        Function(self.0.to_ref())
-    }
-}
+pub struct Function(pub(crate) ValueRef);
 
 /// Contains information about a function.
 ///
@@ -58,7 +34,8 @@ pub struct FunctionInfo {
     ///
     /// Always `None` for Luau.
     pub name_what: Option<&'static str>,
-    /// A string `Lua` if the function is a Lua function, `C` if it is a C function, `main` if it is the main part of a chunk.
+    /// A string `Lua` if the function is a Lua function, `C` if it is a C function, `main` if it is
+    /// the main part of a chunk.
     pub what: &'static str,
     /// Source of the chunk that created the function.
     pub source: Option<String>,
@@ -81,7 +58,7 @@ pub struct CoverageInfo {
     pub hits: Vec<i32>,
 }
 
-impl<'lua> Function<'lua> {
+impl Function {
     /// Calls the function, passing `args` as function arguments.
     ///
     /// The function's return values are converted to the generic type `R`.
@@ -98,7 +75,7 @@ impl<'lua> Function<'lua> {
     ///
     /// let tostring: Function = globals.get("tostring")?;
     ///
-    /// assert_eq!(tostring.call::<_, String>(123)?, "123");
+    /// assert_eq!(tostring.call::<String>(123)?, "123");
     ///
     /// # Ok(())
     /// # }
@@ -117,13 +94,13 @@ impl<'lua> Function<'lua> {
     ///         end
     /// "#).eval()?;
     ///
-    /// assert_eq!(sum.call::<_, u32>((3, 4))?, 3 + 4);
+    /// assert_eq!(sum.call::<u32>((3, 4))?, 3 + 4);
     ///
     /// # Ok(())
     /// # }
     /// ```
-    pub fn call<A: IntoLuaMulti<'lua>, R: FromLuaMulti<'lua>>(&self, args: A) -> Result<R> {
-        let lua = self.0.lua;
+    pub fn call<R: FromLuaMulti>(&self, args: impl IntoLuaMulti) -> Result<R> {
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
@@ -134,7 +111,7 @@ impl<'lua> Function<'lua> {
             let stack_start = ffi::lua_gettop(state);
             // Push function and the arguments
             lua.push_ref(&self.0);
-            let nargs = args.push_into_stack_multi(lua)?;
+            let nargs = args.push_into_stack_multi(&lua)?;
             // Call the function
             let ret = ffi::lua_pcall(state, nargs, ffi::LUA_MULTRET, stack_start);
             if ret != ffi::LUA_OK {
@@ -142,7 +119,7 @@ impl<'lua> Function<'lua> {
             }
             // Get the results
             let nresults = ffi::lua_gettop(state) - stack_start;
-            R::from_stack_multi(nresults, lua)
+            R::from_stack_multi(nresults, &lua)
         }
     }
 
@@ -176,17 +153,18 @@ impl<'lua> Function<'lua> {
     /// [`AsyncThread`]: crate::AsyncThread
     #[cfg(feature = "async")]
     #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
-    pub fn call_async<A, R>(&self, args: A) -> impl Future<Output = Result<R>> + 'lua
+    pub fn call_async<R>(&self, args: impl IntoLuaMulti) -> impl Future<Output = Result<R>>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua,
+        R: FromLuaMulti,
     {
-        let lua = self.0.lua;
-        let thread_res = lua.create_recycled_thread(self).map(|th| {
-            let mut th = th.into_async(args);
-            th.set_recyclable(true);
-            th
-        });
+        let lua = self.0.lua.lock();
+        let thread_res = unsafe {
+            lua.create_recycled_thread(self).map(|th| {
+                let mut th = th.into_async(args);
+                th.set_recyclable(true);
+                th
+            })
+        };
         async move { thread_res?.await }
     }
 
@@ -209,15 +187,15 @@ impl<'lua> Function<'lua> {
     /// "#).eval()?;
     ///
     /// let bound_a = sum.bind(1)?;
-    /// assert_eq!(bound_a.call::<_, u32>(2)?, 1 + 2);
+    /// assert_eq!(bound_a.call::<u32>(2)?, 1 + 2);
     ///
     /// let bound_a_and_b = sum.bind(13)?.bind(57)?;
-    /// assert_eq!(bound_a_and_b.call::<_, u32>(())?, 13 + 57);
+    /// assert_eq!(bound_a_and_b.call::<u32>(())?, 13 + 57);
     ///
     /// # Ok(())
     /// # }
     /// ```
-    pub fn bind<A: IntoLuaMulti<'lua>>(&self, args: A) -> Result<Function<'lua>> {
+    pub fn bind(&self, args: impl IntoLuaMulti) -> Result<Function> {
         unsafe extern "C-unwind" fn args_wrapper_impl(state: *mut ffi::lua_State) -> c_int {
             let nargs = ffi::lua_gettop(state);
             let nbinds = ffi::lua_tointeger(state, ffi::lua_upvalueindex(1)) as c_int;
@@ -233,10 +211,10 @@ impl<'lua> Function<'lua> {
             nargs + nbinds
         }
 
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
 
-        let args = args.into_lua_multi(lua)?;
+        let args = args.into_lua_multi(lua.lua())?;
         let nargs = args.len() as c_int;
 
         if nargs == 0 {
@@ -252,7 +230,7 @@ impl<'lua> Function<'lua> {
             check_stack(state, nargs + 3)?;
 
             ffi::lua_pushinteger(state, nargs as ffi::lua_Integer);
-            for arg in args {
+            for arg in &args {
                 lua.push_value(arg)?;
             }
             protect_lua!(state, nargs + 1, 1, fn(state) {
@@ -262,6 +240,7 @@ impl<'lua> Function<'lua> {
             Function(lua.pop_ref())
         };
 
+        let lua = lua.lua();
         lua.load(
             r#"
             local func, args_wrapper = ...
@@ -272,7 +251,7 @@ impl<'lua> Function<'lua> {
         )
         .try_cache()
         .set_name("__mlua_bind")
-        .call((self.clone(), args_wrapper))
+        .call((self, args_wrapper))
     }
 
     /// Returns the environment of the Lua function.
@@ -281,7 +260,7 @@ impl<'lua> Function<'lua> {
     ///
     /// This function always returns `None` for Rust/C functions.
     pub fn environment(&self) -> Option<Table> {
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
@@ -318,7 +297,7 @@ impl<'lua> Function<'lua> {
     ///
     /// This function does nothing for Rust/C functions.
     pub fn set_environment(&self, env: Table) -> Result<bool> {
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
@@ -342,6 +321,7 @@ impl<'lua> Function<'lua> {
                         ffi::lua_pop(state, 1);
                         // Create an anonymous function with the new environment
                         let f_with_env = lua
+                            .lua()
                             .load("return _ENV")
                             .set_environment(env)
                             .try_cache()
@@ -364,7 +344,7 @@ impl<'lua> Function<'lua> {
     ///
     /// [`lua_getinfo`]: https://www.lua.org/manual/5.4/manual.html#lua_getinfo
     pub fn info(&self) -> FunctionInfo {
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
@@ -425,7 +405,7 @@ impl<'lua> Function<'lua> {
             0
         }
 
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         let mut data: Vec<u8> = Vec::new();
         unsafe {
@@ -443,8 +423,8 @@ impl<'lua> Function<'lua> {
 
     /// Retrieves recorded coverage information about this Lua function including inner calls.
     ///
-    /// This function takes a callback as an argument and calls it providing [`CoverageInfo`] snapshot
-    /// per each executed inner function.
+    /// This function takes a callback as an argument and calls it providing [`CoverageInfo`]
+    /// snapshot per each executed inner function.
     ///
     /// Recording of coverage information is controlled by [`Compiler::set_coverage_level`] option.
     ///
@@ -482,7 +462,7 @@ impl<'lua> Function<'lua> {
             });
         }
 
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
@@ -494,123 +474,117 @@ impl<'lua> Function<'lua> {
         }
     }
 
-    /// Convert this handle to owned version.
-    #[cfg(all(feature = "unstable", any(not(feature = "send"), doc)))]
-    #[cfg_attr(docsrs, doc(cfg(all(feature = "unstable", not(feature = "send")))))]
+    /// Converts this function to a generic C pointer.
+    ///
+    /// There is no way to convert the pointer back to its original value.
+    ///
+    /// Typically this function is used only for hashing and debug information.
     #[inline]
-    pub fn into_owned(self) -> OwnedFunction {
-        OwnedFunction(self.0.into_owned())
+    pub fn to_pointer(&self) -> *const c_void {
+        self.0.to_pointer()
+    }
+
+    /// Creates a deep clone of the Lua 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_attr(docsrs, doc(cfg(feature = "luau")))]
+    pub fn deep_clone(&self) -> Self {
+        let lua = self.0.lua.lock();
+        let ref_thread = lua.ref_thread();
+        unsafe {
+            if ffi::lua_iscfunction(ref_thread, self.0.index) != 0 {
+                return self.clone();
+            }
+
+            ffi::lua_clonefunction(ref_thread, self.0.index);
+            Function(lua.pop_ref_thread())
+        }
     }
 }
 
-impl<'lua> PartialEq for Function<'lua> {
+impl PartialEq for Function {
     fn eq(&self, other: &Self) -> bool {
         self.0 == other.0
     }
 }
 
-// Additional shortcuts
-#[cfg(feature = "unstable")]
-impl OwnedFunction {
-    /// Calls the function, passing `args` as function arguments.
-    ///
-    /// This is a shortcut for [`Function::call()`].
-    #[inline]
-    pub fn call<'lua, A, R>(&'lua self, args: A) -> Result<R>
-    where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua>,
-    {
-        self.to_ref().call(args)
-    }
-
-    /// Returns a future that, when polled, calls `self`, passing `args` as function arguments,
-    /// and drives the execution.
-    ///
-    /// This is a shortcut for [`Function::call_async()`].
-    #[cfg(feature = "async")]
-    #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
-    #[inline]
-    pub async fn call_async<'lua, A, R>(&'lua self, args: A) -> Result<R>
-    where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua,
-    {
-        self.to_ref().call_async(args).await
-    }
-}
-
-pub(crate) struct WrappedFunction<'lua>(pub(crate) Callback<'lua, 'static>);
+pub(crate) struct WrappedFunction(pub(crate) Callback);
 
 #[cfg(feature = "async")]
-pub(crate) struct WrappedAsyncFunction<'lua>(pub(crate) AsyncCallback<'lua, 'static>);
+pub(crate) struct WrappedAsyncFunction(pub(crate) AsyncCallback);
 
-impl<'lua> Function<'lua> {
-    /// Wraps a Rust function or closure, returning an opaque type that implements [`IntoLua`] trait.
+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<'lua>
+    pub fn wrap<A, R, F>(func: F) -> impl IntoLua
     where
-        A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
-        F: Fn(&'lua Lua, A) -> 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, args)?.push_into_stack_multi(lua)
+            func(lua.lua(), 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<'lua>
+    pub fn wrap_mut<A, R, F>(func: F) -> impl IntoLua
     where
-        A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
-        F: FnMut(&'lua Lua, A) -> 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 mut func = func.try_borrow_mut().map_err(|_| Error::RecursiveMutCallback)?;
             let args = A::from_stack_args(nargs, 1, None, lua)?;
-            func(lua, args)?.push_into_stack_multi(lua)
+            func(lua.lua(), args)?.push_into_stack_multi(lua)
         }))
     }
 
-    /// Wraps a Rust async function or closure, returning an opaque type that implements [`IntoLua`] trait.
+    /// Wraps a Rust async function or closure, returning an opaque type that implements [`IntoLua`]
+    /// trait.
     #[cfg(feature = "async")]
     #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
-    pub fn wrap_async<A, R, F, FR>(func: F) -> impl IntoLua<'lua>
+    pub fn wrap_async<A, R, F, FR>(func: F) -> impl IntoLua
     where
-        A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
-        F: Fn(&'lua Lua, A) -> FR + MaybeSend + 'static,
-        FR: Future<Output = Result<R>> + 'lua,
+        A: FromLuaMulti,
+        R: IntoLuaMulti,
+        F: Fn(Lua, A) -> FR + MaybeSend + 'static,
+        FR: Future<Output = Result<R>> + MaybeSend + 'static,
     {
-        WrappedAsyncFunction(Box::new(move |lua, args| unsafe {
-            let args = match A::from_lua_args(args, 1, None, lua) {
+        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::err(e)),
+                Err(e) => return Box::pin(future::ready(Err(e))),
             };
-            let fut = func(lua, args);
-            Box::pin(async move { fut.await?.push_into_stack_multi(lua) })
+            let lua = rawlua.lua().clone();
+            let fut = func(lua.clone(), args);
+            Box::pin(async move { fut.await?.push_into_stack_multi(lua.raw_lua()) })
         }))
     }
 }
 
-impl<'lua> IntoLua<'lua> for WrappedFunction<'lua> {
+impl IntoLua for WrappedFunction {
     #[inline]
-    fn into_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
-        lua.create_callback(self.0).map(Value::Function)
+    fn into_lua(self, lua: &Lua) -> Result<Value> {
+        lua.lock().create_callback(self.0).map(Value::Function)
     }
 }
 
 #[cfg(feature = "async")]
-impl<'lua> IntoLua<'lua> for WrappedAsyncFunction<'lua> {
+impl IntoLua for WrappedAsyncFunction {
     #[inline]
-    fn into_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
-        lua.create_async_callback(self.0).map(Value::Function)
+    fn into_lua(self, lua: &Lua) -> Result<Value> {
+        lua.lock().create_async_callback(self.0).map(Value::Function)
     }
 }
 
@@ -618,8 +592,8 @@ impl<'lua> IntoLua<'lua> for WrappedAsyncFunction<'lua> {
 mod assertions {
     use super::*;
 
+    #[cfg(not(feature = "send"))]
     static_assertions::assert_not_impl_any!(Function: Send);
-
-    #[cfg(all(feature = "unstable", not(feature = "send")))]
-    static_assertions::assert_not_impl_any!(OwnedFunction: Send);
+    #[cfg(feature = "send")]
+    static_assertions::assert_impl_all!(Function: Send, Sync);
 }

src/hook.rs

@@ -1,12 +1,14 @@
 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 crate::lua::Lua;
+use crate::state::RawLua;
+use crate::types::ReentrantMutexGuard;
 use crate::util::{linenumber_to_usize, ptr_to_lossy_str, ptr_to_str};
 
 /// Contains information about currently executing Lua code.
@@ -18,25 +20,44 @@ use crate::util::{linenumber_to_usize, ptr_to_lossy_str, ptr_to_str};
 ///
 /// [lua_doc]: https://www.lua.org/manual/5.4/manual.html#lua_Debug
 /// [`Lua::set_hook`]: crate::Lua::set_hook
-pub struct Debug<'lua> {
-    lua: &'lua Lua,
+pub struct Debug<'a> {
+    lua: EitherLua<'a>,
     ar: ActivationRecord,
     #[cfg(feature = "luau")]
     level: c_int,
 }
 
-impl<'lua> Debug<'lua> {
+enum EitherLua<'a> {
+    Owned(ReentrantMutexGuard<'a, RawLua>),
     #[cfg(not(feature = "luau"))]
-    pub(crate) fn new(lua: &'lua Lua, ar: *mut lua_Debug) -> Self {
+    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,
+        }
+    }
+}
+
+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 {
         Debug {
-            lua,
+            lua: EitherLua::Borrowed(lua),
             ar: ActivationRecord::Borrowed(ar),
         }
     }
 
-    pub(crate) fn new_owned(lua: &'lua Lua, _level: c_int, ar: lua_Debug) -> Self {
+    pub(crate) fn new_owned(guard: ReentrantMutexGuard<'a, RawLua>, _level: c_int, ar: lua_Debug) -> Self {
         Debug {
-            lua,
+            lua: EitherLua::Owned(guard),
             ar: ActivationRecord::Owned(UnsafeCell::new(ar)),
             #[cfg(feature = "luau")]
             level: _level,
@@ -234,7 +255,8 @@ pub struct DebugSource<'a> {
     pub line_defined: Option<usize>,
     /// The line number where the definition of the function ends (not set by Luau).
     pub last_line_defined: Option<usize>,
-    /// A string `Lua` if the function is a Lua function, `C` if it is a C function, `main` if it is the main part of a chunk.
+    /// A string `Lua` if the function is a Lua function, `C` if it is a C function, `main` if it is
+    /// the main part of a chunk.
     pub what: &'static str,
 }
 
@@ -242,20 +264,10 @@ pub struct DebugSource<'a> {
 pub struct DebugStack {
     pub num_ups: i32,
     /// Requires `feature = "lua54/lua53/lua52/luau"`
-    #[cfg(any(
-        feature = "lua54",
-        feature = "lua53",
-        feature = "lua52",
-        feature = "luau"
-    ))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52", feature = "luau"))]
     pub num_params: i32,
     /// Requires `feature = "lua54/lua53/lua52/luau"`
-    #[cfg(any(
-        feature = "lua54",
-        feature = "lua53",
-        feature = "lua52",
-        feature = "luau"
-    ))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52", feature = "luau"))]
     pub is_vararg: bool,
 }
 

src/lib.rs

@@ -27,9 +27,9 @@
 //!
 //! # Serde support
 //!
-//! The [`LuaSerdeExt`] trait implemented for [`Lua`] allows conversion from Rust types to Lua values
-//! and vice versa using serde. Any user defined data type that implements [`serde::Serialize`] or
-//! [`serde::Deserialize`] can be converted.
+//! The [`LuaSerdeExt`] trait implemented for [`Lua`] allows conversion from Rust types to Lua
+//! values and vice versa using serde. Any user defined data type that implements
+//! [`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
@@ -40,14 +40,14 @@
 //! # 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).
+//! Lua code with async capabilities can be executed by [`call_async`] family of functions or
+//! polling [`AsyncThread`] using any runtime (eg. Tokio).
 //!
 //! Requires `feature = "async"`.
 //!
 //! # `Send` requirement
-//! By default `mlua` is `!Send`. This can be changed by enabling `feature = "send"` that adds `Send` requirement
-//! to [`Function`]s and [`UserData`].
+//! By default `mlua` is `!Send`. This can be changed by enabling `feature = "send"` that adds
+//! `Send` requirement to [`Function`]s and [`UserData`].
 //!
 //! [Lua programming language]: https://www.lua.org/
 //! [`Lua`]: crate::Lua
@@ -73,7 +73,6 @@
 
 // Deny warnings inside doc tests / examples. When this isn't present, rustdoc doesn't show *any*
 // warnings at all.
-#![doc(test(attr(deny(warnings))))]
 #![cfg_attr(docsrs, feature(doc_cfg))]
 
 #[macro_use]
@@ -84,45 +83,44 @@ mod conversion;
 mod error;
 mod function;
 mod hook;
-mod lua;
 #[cfg(feature = "luau")]
 mod luau;
 mod memory;
 mod multi;
-mod scope;
+// mod scope;
+mod state;
 mod stdlib;
 mod string;
 mod table;
 mod thread;
+mod traits;
 mod types;
 mod userdata;
-mod userdata_ext;
-mod userdata_impl;
 mod util;
 mod value;
 
 pub mod prelude;
 
+pub use bstr::BString;
 pub use ffi::{self, lua_CFunction, lua_State};
 
 pub use crate::chunk::{AsChunk, Chunk, ChunkMode};
 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::lua::{GCMode, Lua, LuaOptions};
 pub use crate::multi::Variadic;
-pub use crate::scope::Scope;
+pub use crate::state::{GCMode, Lua, LuaOptions};
+// pub use crate::scope::Scope;
 pub use crate::stdlib::StdLib;
-pub use crate::string::String;
-pub use crate::table::{Table, TableExt, TablePairs, TableSequence};
+pub use crate::string::{BorrowedBytes, BorrowedStr, String};
+pub use crate::table::{Table, TablePairs, TableSequence};
 pub use crate::thread::{Thread, ThreadStatus};
-pub use crate::types::{AppDataRef, AppDataRefMut, Integer, LightUserData, Number, RegistryKey};
+pub use crate::traits::ObjectLike;
+pub use crate::types::{AppDataRef, AppDataRefMut, Integer, LightUserData, MaybeSend, Number, RegistryKey};
 pub use crate::userdata::{
-    AnyUserData, MetaMethod, UserData, UserDataFields, UserDataMetatable, UserDataMethods,
-    UserDataRef, UserDataRefMut,
+    AnyUserData, MetaMethod, UserData, UserDataFields, UserDataMetatable, UserDataMethods, UserDataRef,
+    UserDataRefMut, UserDataRegistry,
 };
-pub use crate::userdata_ext::AnyUserDataExt;
-pub use crate::userdata_impl::UserDataRegistry;
 pub use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, MultiValue, Nil, Value};
 
 #[cfg(not(feature = "luau"))]
@@ -141,9 +139,7 @@ pub use crate::thread::AsyncThread;
 
 #[cfg(feature = "serialize")]
 #[doc(inline)]
-pub use crate::serde::{
-    de::Options as DeserializeOptions, ser::Options as SerializeOptions, LuaSerdeExt,
-};
+pub use crate::serde::{de::Options as DeserializeOptions, ser::Options as SerializeOptions, LuaSerdeExt};
 
 #[cfg(feature = "serialize")]
 #[cfg_attr(docsrs, doc(cfg(feature = "serialize")))]
@@ -154,13 +150,6 @@ pub mod serde;
 #[macro_use]
 extern crate mlua_derive;
 
-// Unstable features
-#[cfg(feature = "unstable")]
-pub use crate::{
-    function::OwnedFunction, string::OwnedString, table::OwnedTable, thread::OwnedThread,
-    userdata::OwnedAnyUserData,
-};
-
 /// Create a type that implements [`AsChunk`] and can capture Rust variables.
 ///
 /// This macro allows to write Lua code directly in Rust code.
@@ -201,8 +190,8 @@ pub use crate::{
 ///
 /// Other minor limitations:
 ///
-/// - Certain escape codes in string literals don't work.
-///   (Specifically: `\a`, `\b`, `\f`, `\v`, `\123` (octal escape codes), `\u`, and `\U`).
+/// - Certain escape codes in string literals don't work. (Specifically: `\a`, `\b`, `\f`, `\v`,
+///   `\123` (octal escape codes), `\u`, and `\U`).
 ///
 ///   These are accepted: : `\\`, `\n`, `\t`, `\r`, `\xAB` (hex escape codes), and `\0`.
 ///
@@ -266,11 +255,13 @@ pub use mlua_derive::FromLua;
 ///     ...
 /// }
 /// ```
-///
 #[cfg(any(feature = "module", docsrs))]
 #[cfg_attr(docsrs, doc(cfg(feature = "module")))]
 pub use mlua_derive::lua_module;
 
+#[cfg(all(feature = "module", feature = "send"))]
+compile_error!("`send` feature is not supported in module mode");
+
 pub(crate) mod private {
     use super::*;
 
@@ -279,6 +270,6 @@ pub(crate) mod private {
     impl Sealed for Error {}
     impl<T> Sealed for std::result::Result<T, Error> {}
     impl Sealed for Lua {}
-    impl Sealed for Table<'_> {}
-    impl Sealed for AnyUserData<'_> {}
+    impl Sealed for Table {}
+    impl Sealed for AnyUserData {}
 }

src/luau/mod.rs

@@ -2,7 +2,7 @@ use std::ffi::CStr;
 use std::os::raw::{c_float, c_int};
 
 use crate::error::Result;
-use crate::lua::Lua;
+use crate::state::Lua;
 
 // Since Luau has some missing standard functions, we re-implement them here
 
@@ -10,10 +10,7 @@ impl Lua {
     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("collectgarbage", self.create_c_function(lua_collectgarbage)?)?;
         globals.raw_set("vector", self.create_c_function(lua_vector)?)?;
 
         // Set `_VERSION` global to include version number

src/luau/package.rs

@@ -7,9 +7,8 @@ use std::{env, fs};
 
 use crate::chunk::ChunkMode;
 use crate::error::Result;
-use crate::lua::Lua;
+use crate::state::Lua;
 use crate::table::Table;
-use crate::types::RegistryKey;
 use crate::value::{IntoLua, Value};
 
 #[cfg(unix)]
@@ -27,9 +26,6 @@ const TARGET_MLUA_LUAU_ABI_VERSION: u32 = 1;
 #[used]
 pub static MLUA_LUAU_ABI_VERSION: u32 = TARGET_MLUA_LUAU_ABI_VERSION;
 
-// We keep reference to the `package` table in registry under this key
-struct PackageKey(RegistryKey);
-
 // We keep reference to the loaded dylibs in application data
 #[cfg(unix)]
 struct LoadedDylibs(FxHashMap<PathBuf, Library>);
@@ -51,9 +47,8 @@ impl std::ops::DerefMut for LoadedDylibs {
 }
 
 pub(crate) fn register_package_module(lua: &Lua) -> Result<()> {
-    // Create the package table and store it in app_data for later use (bypassing globals lookup)
+    // Create the package table
     let package = lua.create_table()?;
-    lua.set_app_data(PackageKey(lua.create_registry_value(package.clone())?));
 
     // Set `package.path`
     let mut search_path = env::var("LUAU_PATH")
@@ -81,13 +76,19 @@ pub(crate) fn register_package_module(lua: &Lua) -> Result<()> {
     }
 
     // Set `package.loaded` (table with a list of loaded modules)
-    let loaded = lua.create_table()?;
-    package.raw_set("loaded", loaded.clone())?;
-    lua.set_named_registry_value("_LOADED", loaded)?;
+    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.clone())?;
+    package.raw_set("loaders", &loaders)?;
     #[cfg(unix)]
     {
         loaders.push(lua.create_function(dylib_loader)?)?;
@@ -97,12 +98,14 @@ pub(crate) fn register_package_module(lua: &Lua) -> Result<()> {
 
     // Register the module and `require` function in globals
     let globals = lua.globals();
-    globals.raw_set("package", package)?;
+    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
@@ -190,17 +193,17 @@ fn package_searchpath(name: &str, search_path: &str, try_prefix: bool) -> Option
 /// Tries to load a lua (text) file
 fn lua_loader(lua: &Lua, modname: StdString) -> Result<Value> {
     let package = {
-        let key = lua.app_data_ref::<PackageKey>().unwrap();
-        lua.registry_value::<Table>(&key.0)
+        let loaded = lua.named_registry_value::<Table>("_LOADED")?;
+        loaded.raw_get::<Table>("package")
     }?;
-    let search_path = package.get::<_, StdString>("path").unwrap_or_default();
+    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_name(format!("={}", file_path.display()))
                     .set_mode(ChunkMode::Text)
                     .into_function()
                     .map(Value::Function);
@@ -218,20 +221,19 @@ fn lua_loader(lua: &Lua, modname: StdString) -> Result<Value> {
 #[cfg(unix)]
 fn dylib_loader(lua: &Lua, modname: StdString) -> Result<Value> {
     let package = {
-        let key = lua.app_data_ref::<PackageKey>().unwrap();
-        lua.registry_value::<Table>(&key.0)
+        let loaded = lua.named_registry_value::<Table>("_LOADED")?;
+        loaded.raw_get::<Table>("package")
     }?;
-    let search_cpath = package.get::<_, StdString>("cpath").unwrap_or_default();
+    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())
-        {
+        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(),
-        ) {
+        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)

src/macros.rs

@@ -10,8 +10,7 @@ macro_rules! bug_msg {
 
 macro_rules! cstr {
     ($s:expr) => {
-        concat!($s, "\0") as *const str as *const [::std::os::raw::c_char]
-            as *const ::std::os::raw::c_char
+        concat!($s, "\0") as *const str as *const [::std::os::raw::c_char] as *const ::std::os::raw::c_char
     };
 }
 

src/multi.rs

@@ -4,105 +4,101 @@ use std::os::raw::c_int;
 use std::result::Result as StdResult;
 
 use crate::error::Result;
-use crate::lua::Lua;
+use crate::state::{Lua, RawLua};
 use crate::util::check_stack;
 use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, MultiValue, Nil};
 
 /// 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<'lua, T: IntoLua<'lua>, E: IntoLua<'lua>> IntoLuaMulti<'lua> for StdResult<T, E> {
+impl<T: IntoLua, E: IntoLua> IntoLuaMulti for StdResult<T, E> {
     #[inline]
-    fn into_lua_multi(self, lua: &'lua Lua) -> Result<MultiValue<'lua>> {
-        let mut result = MultiValue::with_lua_and_capacity(lua, 2);
+    fn into_lua_multi(self, lua: &Lua) -> Result<MultiValue> {
         match self {
-            Ok(v) => result.push_front(v.into_lua(lua)?),
-            Err(e) => {
-                result.push_front(e.into_lua(lua)?);
-                result.push_front(Nil);
-            }
+            Ok(val) => (val,).into_lua_multi(lua),
+            Err(err) => (Nil, err).into_lua_multi(lua),
         }
-        Ok(result)
     }
-}
 
-impl<'lua, E: IntoLua<'lua>> IntoLuaMulti<'lua> for StdResult<(), E> {
     #[inline]
-    fn into_lua_multi(self, lua: &'lua Lua) -> Result<MultiValue<'lua>> {
+    unsafe fn push_into_stack_multi(self, lua: &RawLua) -> Result<c_int> {
         match self {
-            Ok(_) => return Ok(MultiValue::new()),
-            Err(e) => {
-                let mut result = MultiValue::with_lua_and_capacity(lua, 2);
-                result.push_front(e.into_lua(lua)?);
-                result.push_front(Nil);
-                Ok(result)
-            }
+            Ok(val) => (val,).push_into_stack_multi(lua),
+            Err(err) => (Nil, err).push_into_stack_multi(lua),
         }
     }
 }
 
-impl<'lua, T: IntoLua<'lua>> IntoLuaMulti<'lua> for T {
+impl<E: IntoLua> IntoLuaMulti for StdResult<(), E> {
     #[inline]
-    fn into_lua_multi(self, lua: &'lua Lua) -> Result<MultiValue<'lua>> {
-        let mut v = MultiValue::with_lua_and_capacity(lua, 1);
-        v.push_front(self.into_lua(lua)?);
+    fn into_lua_multi(self, lua: &Lua) -> Result<MultiValue> {
+        match self {
+            Ok(_) => const { Ok(MultiValue::new()) },
+            Err(err) => (Nil, err).into_lua_multi(lua),
+        }
+    }
+
+    #[inline]
+    unsafe fn push_into_stack_multi(self, lua: &RawLua) -> Result<c_int> {
+        match self {
+            Ok(_) => Ok(0),
+            Err(err) => (Nil, err).push_into_stack_multi(lua),
+        }
+    }
+}
+
+impl<T: IntoLua> IntoLuaMulti for T {
+    #[inline]
+    fn into_lua_multi(self, lua: &Lua) -> Result<MultiValue> {
+        let mut v = MultiValue::with_capacity(1);
+        v.push_back(self.into_lua(lua)?);
         Ok(v)
     }
 
     #[inline]
-    unsafe fn push_into_stack_multi(self, lua: &'lua Lua) -> Result<c_int> {
+    unsafe fn push_into_stack_multi(self, lua: &RawLua) -> Result<c_int> {
         self.push_into_stack(lua)?;
         Ok(1)
     }
 }
 
-impl<'lua, T: FromLua<'lua>> FromLuaMulti<'lua> for T {
+impl<T: FromLua> FromLuaMulti for T {
     #[inline]
-    fn from_lua_multi(mut values: MultiValue<'lua>, lua: &'lua Lua) -> Result<Self> {
+    fn from_lua_multi(mut values: MultiValue, lua: &Lua) -> Result<Self> {
         T::from_lua(values.pop_front().unwrap_or(Nil), lua)
     }
 
     #[inline]
-    fn from_lua_args(
-        mut args: MultiValue<'lua>,
-        i: usize,
-        to: Option<&str>,
-        lua: &'lua Lua,
-    ) -> Result<Self> {
+    fn from_lua_args(mut args: MultiValue, i: usize, to: Option<&str>, lua: &Lua) -> Result<Self> {
         T::from_lua_arg(args.pop_front().unwrap_or(Nil), i, to, lua)
     }
 
     #[inline]
-    unsafe fn from_stack_multi(nvals: c_int, lua: &'lua Lua) -> Result<Self> {
+    unsafe fn from_stack_multi(nvals: c_int, lua: &RawLua) -> Result<Self> {
         if nvals == 0 {
-            return T::from_lua(Nil, lua);
+            return T::from_lua(Nil, lua.lua());
         }
         T::from_stack(-nvals, lua)
     }
 
     #[inline]
-    unsafe fn from_stack_args(
-        nargs: c_int,
-        i: usize,
-        to: Option<&str>,
-        lua: &'lua Lua,
-    ) -> Result<Self> {
+    unsafe fn from_stack_args(nargs: c_int, i: usize, to: Option<&str>, lua: &RawLua) -> Result<Self> {
         if nargs == 0 {
-            return T::from_lua_arg(Nil, i, to, lua);
+            return T::from_lua_arg(Nil, i, to, lua.lua());
         }
         T::from_stack_arg(-nargs, i, to, lua)
     }
 }
 
-impl<'lua> IntoLuaMulti<'lua> for MultiValue<'lua> {
+impl IntoLuaMulti for MultiValue {
     #[inline]
-    fn into_lua_multi(self, _: &'lua Lua) -> Result<MultiValue<'lua>> {
+    fn into_lua_multi(self, _: &Lua) -> Result<MultiValue> {
         Ok(self)
     }
 }
 
-impl<'lua> FromLuaMulti<'lua> for MultiValue<'lua> {
+impl FromLuaMulti for MultiValue {
     #[inline]
-    fn from_lua_multi(values: MultiValue<'lua>, _: &'lua Lua) -> Result<Self> {
+    fn from_lua_multi(values: MultiValue, _: &Lua) -> Result<Self> {
         Ok(values)
     }
 }
@@ -145,7 +141,7 @@ impl<T> Variadic<T> {
 
 impl<T> Default for Variadic<T> {
     fn default() -> Variadic<T> {
-        Variadic::new()
+        const { Variadic::new() }
     }
 }
 
@@ -178,21 +174,19 @@ impl<T> DerefMut for Variadic<T> {
     }
 }
 
-impl<'lua, T: IntoLua<'lua>> IntoLuaMulti<'lua> for Variadic<T> {
+impl<T: IntoLua> IntoLuaMulti for Variadic<T> {
     #[inline]
-    fn into_lua_multi(self, lua: &'lua Lua) -> Result<MultiValue<'lua>> {
-        let mut values = MultiValue::with_lua_and_capacity(lua, self.0.len());
-        values.refill(self.0.into_iter().map(|e| e.into_lua(lua)))?;
-        Ok(values)
+    fn into_lua_multi(self, lua: &Lua) -> Result<MultiValue> {
+        MultiValue::from_lua_iter(lua, self)
     }
 }
 
-impl<'lua, T: FromLua<'lua>> FromLuaMulti<'lua> for Variadic<T> {
+impl<T: FromLua> FromLuaMulti for Variadic<T> {
     #[inline]
-    fn from_lua_multi(mut values: MultiValue<'lua>, lua: &'lua Lua) -> Result<Self> {
+    fn from_lua_multi(mut values: MultiValue, lua: &Lua) -> Result<Self> {
         values
-            .drain_all()
-            .map(|e| T::from_lua(e, lua))
+            .drain(..)
+            .map(|val| T::from_lua(val, lua))
             .collect::<Result<Vec<T>>>()
             .map(Variadic)
     }
@@ -200,26 +194,26 @@ impl<'lua, T: FromLua<'lua>> FromLuaMulti<'lua> for Variadic<T> {
 
 macro_rules! impl_tuple {
     () => (
-        impl<'lua> IntoLuaMulti<'lua> for () {
+        impl IntoLuaMulti for () {
             #[inline]
-            fn into_lua_multi(self, lua: &'lua Lua) -> Result<MultiValue<'lua>> {
-                Ok(MultiValue::with_lua_and_capacity(lua, 0))
+            fn into_lua_multi(self, _: &Lua) -> Result<MultiValue> {
+                const { Ok(MultiValue::new()) }
             }
 
             #[inline]
-            unsafe fn push_into_stack_multi(self, _lua: &'lua Lua) -> Result<c_int> {
+            unsafe fn push_into_stack_multi(self, _lua: &RawLua) -> Result<c_int> {
                 Ok(0)
             }
         }
 
-        impl<'lua> FromLuaMulti<'lua> for () {
+        impl FromLuaMulti for () {
             #[inline]
-            fn from_lua_multi(_values: MultiValue<'lua>, _lua: &'lua Lua) -> Result<Self> {
+            fn from_lua_multi(_values: MultiValue, _lua: &Lua) -> Result<Self> {
                 Ok(())
             }
 
             #[inline]
-            unsafe fn from_stack_multi(nvals: c_int, lua: &'lua Lua) -> Result<Self> {
+            unsafe fn from_stack_multi(nvals: c_int, lua: &RawLua) -> Result<Self> {
                 if nvals > 0 {
                     ffi::lua_pop(lua.state(), nvals);
                 }
@@ -229,13 +223,13 @@ macro_rules! impl_tuple {
     );
 
     ($last:ident $($name:ident)*) => (
-        impl<'lua, $($name,)* $last> IntoLuaMulti<'lua> for ($($name,)* $last,)
-            where $($name: IntoLua<'lua>,)*
-                  $last: IntoLuaMulti<'lua>
+        impl<$($name,)* $last> IntoLuaMulti for ($($name,)* $last,)
+            where $($name: IntoLua,)*
+                  $last: IntoLuaMulti
         {
             #[allow(unused_mut, non_snake_case)]
             #[inline]
-            fn into_lua_multi(self, lua: &'lua Lua) -> Result<MultiValue<'lua>> {
+            fn into_lua_multi(self, lua: &Lua) -> Result<MultiValue> {
                 let ($($name,)* $last,) = self;
 
                 let mut results = $last.into_lua_multi(lua)?;
@@ -245,7 +239,7 @@ macro_rules! impl_tuple {
 
             #[allow(non_snake_case)]
             #[inline]
-            unsafe fn push_into_stack_multi(self, lua: &'lua Lua) -> Result<c_int> {
+            unsafe fn push_into_stack_multi(self, lua: &RawLua) -> Result<c_int> {
                 let ($($name,)* $last,) = self;
                 let mut nresults = 0;
                 $(
@@ -261,13 +255,13 @@ macro_rules! impl_tuple {
             }
         }
 
-        impl<'lua, $($name,)* $last> FromLuaMulti<'lua> for ($($name,)* $last,)
-            where $($name: FromLua<'lua>,)*
-                  $last: FromLuaMulti<'lua>
+        impl<$($name,)* $last> FromLuaMulti for ($($name,)* $last,)
+            where $($name: FromLua,)*
+                  $last: FromLuaMulti
         {
             #[allow(unused_mut, non_snake_case)]
             #[inline]
-            fn from_lua_multi(mut values: MultiValue<'lua>, lua: &'lua Lua) -> Result<Self> {
+            fn from_lua_multi(mut values: MultiValue, lua: &Lua) -> Result<Self> {
                 $(let $name = FromLua::from_lua(values.pop_front().unwrap_or(Nil), lua)?;)*
                 let $last = FromLuaMulti::from_lua_multi(values, lua)?;
                 Ok(($($name,)* $last,))
@@ -275,7 +269,7 @@ macro_rules! impl_tuple {
 
             #[allow(unused_mut, non_snake_case)]
             #[inline]
-            fn from_lua_args(mut args: MultiValue<'lua>, mut i: usize, to: Option<&str>, lua: &'lua Lua) -> Result<Self> {
+            fn from_lua_args(mut args: MultiValue, mut i: usize, to: Option<&str>, lua: &Lua) -> Result<Self> {
                 $(
                     let $name = FromLua::from_lua_arg(args.pop_front().unwrap_or(Nil), i, to, lua)?;
                     i += 1;
@@ -286,13 +280,13 @@ macro_rules! impl_tuple {
 
             #[allow(unused_mut, non_snake_case)]
             #[inline]
-            unsafe fn from_stack_multi(mut nvals: c_int, lua: &'lua Lua) -> Result<Self> {
+            unsafe fn from_stack_multi(mut nvals: c_int, lua: &RawLua) -> Result<Self> {
                 $(
                     let $name = if nvals > 0 {
                         nvals -= 1;
                         FromLua::from_stack(-(nvals + 1), lua)
                     } else {
-                        FromLua::from_lua(Nil, lua)
+                        FromLua::from_lua(Nil, lua.lua())
                     }?;
                 )*
                 let $last = FromLuaMulti::from_stack_multi(nvals, lua)?;
@@ -301,13 +295,13 @@ macro_rules! impl_tuple {
 
             #[allow(unused_mut, non_snake_case)]
             #[inline]
-            unsafe fn from_stack_args(mut nargs: c_int, mut i: usize, to: Option<&str>, lua: &'lua Lua) -> Result<Self> {
+            unsafe fn from_stack_args(mut nargs: c_int, mut i: usize, to: Option<&str>, lua: &RawLua) -> Result<Self> {
                 $(
                     let $name = if nargs > 0 {
                         nargs -= 1;
                         FromLua::from_stack_arg(-(nargs + 1), i, to, lua)
                     } else {
-                        FromLua::from_lua_arg(Nil, i, to, lua)
+                        FromLua::from_lua_arg(Nil, i, to, lua.lua())
                     }?;
                     i += 1;
                 )*

src/prelude.rs

@@ -2,19 +2,17 @@
 
 #[doc(no_inline)]
 pub use crate::{
-    AnyUserData as LuaAnyUserData, AnyUserDataExt as LuaAnyUserDataExt, Chunk as LuaChunk,
-    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, RegistryKey as LuaRegistryKey,
-    Result as LuaResult, StdLib as LuaStdLib, String as LuaString, Table as LuaTable,
-    TableExt as LuaTableExt, 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,
+    AnyUserData as LuaAnyUserData, Chunk as LuaChunk, 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,
 };
 
 #[cfg(not(feature = "luau"))]
@@ -32,13 +30,5 @@ pub use crate::AsyncThread as LuaAsyncThread;
 #[cfg(feature = "serialize")]
 #[doc(no_inline)]
 pub use crate::{
-    DeserializeOptions as LuaDeserializeOptions, LuaSerdeExt,
-    SerializeOptions as LuaSerializeOptions,
-};
-
-#[cfg(feature = "unstable")]
-#[doc(no_inline)]
-pub use crate::{
-    OwnedAnyUserData as LuaOwnedAnyUserData, OwnedFunction as LuaOwnedFunction,
-    OwnedString as LuaOwnedString, OwnedTable as LuaOwnedTable, OwnedThread as LuaOwnedThread,
+    DeserializeOptions as LuaDeserializeOptions, LuaSerdeExt, SerializeOptions as LuaSerializeOptions,
 };

src/scope.rs

@@ -10,7 +10,7 @@ use serde::Serialize;
 use crate::error::{Error, Result};
 use crate::function::Function;
 use crate::lua::Lua;
-use crate::types::{Callback, CallbackUpvalue, LuaRef, MaybeSend, SubtypeId};
+use crate::types::{Callback, CallbackUpvalue, MaybeSend, SubtypeId, ValueRef};
 use crate::userdata::{
     AnyUserData, MetaMethod, UserData, UserDataCell, UserDataFields, UserDataMethods,
 };
@@ -19,7 +19,7 @@ use crate::util::{
     self, assert_stack, check_stack, init_userdata_metatable, push_string, push_table,
     rawset_field, short_type_name, take_userdata, StackGuard,
 };
-use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, Value};
+use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti};
 
 #[cfg(feature = "lua54")]
 use crate::userdata::USER_VALUE_MAXSLOT;
@@ -38,11 +38,11 @@ where
     'lua: 'scope,
 {
     lua: &'lua Lua,
-    destructors: RefCell<Vec<(LuaRef<'lua>, DestructorCallback<'lua>)>>,
+    destructors: RefCell<Vec<(ValueRef<'lua>, DestructorCallback<'lua>)>>,
     _scope_invariant: PhantomData<Cell<&'scope ()>>,
 }
 
-type DestructorCallback<'lua> = Box<dyn Fn(LuaRef<'lua>) -> Vec<Box<dyn Any>> + 'lua>;
+type DestructorCallback<'lua> = Box<dyn Fn(ValueRef<'lua>) -> Vec<Box<dyn Any>> + 'lua>;
 
 impl<'lua, 'scope> Scope<'lua, 'scope> {
     pub(crate) fn new(lua: &'lua Lua) -> Scope<'lua, 'scope> {
@@ -63,7 +63,7 @@ impl<'lua, 'scope> Scope<'lua, 'scope> {
     pub fn create_function<'callback, A, R, F>(&'callback self, func: F) -> Result<Function<'lua>>
     where
         A: FromLuaMulti<'callback>,
-        R: IntoLuaMulti<'callback>,
+        R: IntoLuaMulti,
         F: Fn(&'callback Lua, A) -> Result<R> + 'scope,
     {
         // Safe, because 'scope must outlive 'callback (due to Self containing 'scope), however the
@@ -97,7 +97,7 @@ impl<'lua, 'scope> Scope<'lua, 'scope> {
     ) -> Result<Function<'lua>>
     where
         A: FromLuaMulti<'callback>,
-        R: IntoLuaMulti<'callback>,
+        R: IntoLuaMulti,
         F: FnMut(&'callback Lua, A) -> Result<R> + 'scope,
     {
         let func = RefCell::new(func);
@@ -405,7 +405,7 @@ impl<'lua, 'scope> Scope<'lua, 'scope> {
             let meta_methods_nrec = registry.meta_methods.len() + registry.meta_fields.len() + 1;
             push_table(state, 0, meta_methods_nrec, true)?;
             for (k, m) in registry.meta_methods {
-                lua.push_value(Value::Function(wrap_method(self, ud_ptr, &k, m)?))?;
+                lua.push(wrap_method(self, ud_ptr, &k, m)?)?;
                 rawset_field(state, -2, MetaMethod::validate(&k)?)?;
             }
             let mut has_name = false;
@@ -455,7 +455,7 @@ impl<'lua, 'scope> Scope<'lua, 'scope> {
             if field_getters_nrec > 0 {
                 push_table(state, 0, field_getters_nrec, true)?;
                 for (k, m) in registry.field_getters {
-                    lua.push_value(Value::Function(wrap_method(self, ud_ptr, &k, m)?))?;
+                    lua.push(wrap_method(self, ud_ptr, &k, m)?)?;
                     rawset_field(state, -2, &k)?;
                 }
                 field_getters_index = Some(ffi::lua_absindex(state, -1));
@@ -466,7 +466,7 @@ impl<'lua, 'scope> Scope<'lua, 'scope> {
             if field_setters_nrec > 0 {
                 push_table(state, 0, field_setters_nrec, true)?;
                 for (k, m) in registry.field_setters {
-                    lua.push_value(Value::Function(wrap_method(self, ud_ptr, &k, m)?))?;
+                    lua.push(wrap_method(self, ud_ptr, &k, m)?)?;
                     rawset_field(state, -2, &k)?;
                 }
                 field_setters_index = Some(ffi::lua_absindex(state, -1));
@@ -478,7 +478,7 @@ impl<'lua, 'scope> Scope<'lua, 'scope> {
                 // Create table used for methods lookup
                 push_table(state, 0, methods_nrec, true)?;
                 for (k, m) in registry.methods {
-                    lua.push_value(Value::Function(wrap_method(self, ud_ptr, &k, m)?))?;
+                    lua.push(wrap_method(self, ud_ptr, &k, m)?)?;
                     rawset_field(state, -2, &k)?;
                 }
                 methods_index = Some(ffi::lua_absindex(state, -1));
@@ -656,7 +656,7 @@ impl<'lua, T> NonStaticUserDataRegistry<'lua, T> {
 impl<'lua, T> UserDataFields<'lua, T> for NonStaticUserDataRegistry<'lua, T> {
     fn add_field<V>(&mut self, name: impl AsRef<str>, value: V)
     where
-        V: IntoLua<'lua> + Clone + 'static,
+        V: IntoLua + Clone + 'static,
     {
         let name = name.as_ref().to_string();
         self.fields.push((
@@ -670,7 +670,7 @@ impl<'lua, T> UserDataFields<'lua, T> for NonStaticUserDataRegistry<'lua, T> {
     fn add_field_method_get<M, R>(&mut self, name: impl AsRef<str>, method: M)
     where
         M: Fn(&'lua Lua, &T) -> Result<R> + MaybeSend + 'static,
-        R: IntoLua<'lua>,
+        R: IntoLua,
     {
         let method = NonStaticMethod::Method(Box::new(move |lua, ud, _| unsafe {
             method(lua, ud)?.push_into_stack_multi(lua)
@@ -694,7 +694,7 @@ impl<'lua, T> UserDataFields<'lua, T> for NonStaticUserDataRegistry<'lua, T> {
     fn add_field_function_get<F, R>(&mut self, name: impl AsRef<str>, function: F)
     where
         F: Fn(&'lua Lua, AnyUserData<'lua>) -> Result<R> + MaybeSend + 'static,
-        R: IntoLua<'lua>,
+        R: IntoLua,
     {
         let func_name = format!("{}.{}", short_type_name::<T>(), name.as_ref());
         let func = NonStaticMethod::Function(Box::new(move |lua, nargs| unsafe {
@@ -719,7 +719,7 @@ impl<'lua, T> UserDataFields<'lua, T> for NonStaticUserDataRegistry<'lua, T> {
 
     fn add_meta_field<V>(&mut self, name: impl AsRef<str>, value: V)
     where
-        V: IntoLua<'lua> + Clone + 'static,
+        V: IntoLua + Clone + 'static,
     {
         let name = name.as_ref().to_string();
         let name2 = name.clone();
@@ -735,7 +735,7 @@ impl<'lua, T> UserDataFields<'lua, T> for NonStaticUserDataRegistry<'lua, T> {
     fn add_meta_field_with<F, R>(&mut self, name: impl AsRef<str>, f: F)
     where
         F: Fn(&'lua Lua) -> Result<R> + MaybeSend + 'static,
-        R: IntoLua<'lua>,
+        R: IntoLua,
     {
         let name = name.as_ref().to_string();
         let name2 = name.clone();
@@ -754,7 +754,7 @@ impl<'lua, T> UserDataMethods<'lua, T> for NonStaticUserDataRegistry<'lua, T> {
     where
         M: Fn(&'lua Lua, &T, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
+        R: IntoLuaMulti,
     {
         let func_name = format!("{}.{}", short_type_name::<T>(), name.as_ref());
         let method = NonStaticMethod::Method(Box::new(move |lua, ud, nargs| unsafe {
@@ -768,7 +768,7 @@ impl<'lua, T> UserDataMethods<'lua, T> for NonStaticUserDataRegistry<'lua, T> {
     where
         M: FnMut(&'lua Lua, &mut T, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
+        R: IntoLuaMulti,
     {
         let func_name = format!("{}.{}", short_type_name::<T>(), name.as_ref());
         let method = NonStaticMethod::MethodMut(Box::new(move |lua, ud, nargs| unsafe {
@@ -786,7 +786,7 @@ impl<'lua, T> UserDataMethods<'lua, T> for NonStaticUserDataRegistry<'lua, T> {
         M: Fn(&'lua Lua, &'s T, A) -> MR + MaybeSend + 'static,
         A: FromLuaMulti<'lua>,
         MR: Future<Output = Result<R>> + 's,
-        R: IntoLuaMulti<'lua>,
+        R: IntoLuaMulti,
     {
         // The panic should never happen as async non-static code wouldn't compile
         // Non-static lifetime must be bounded to 'lua lifetime
@@ -801,7 +801,7 @@ impl<'lua, T> UserDataMethods<'lua, T> for NonStaticUserDataRegistry<'lua, T> {
         M: Fn(&'lua Lua, &'s mut T, A) -> MR + MaybeSend + 'static,
         A: FromLuaMulti<'lua>,
         MR: Future<Output = Result<R>> + 's,
-        R: IntoLuaMulti<'lua>,
+        R: IntoLuaMulti,
     {
         // The panic should never happen as async non-static code wouldn't compile
         // Non-static lifetime must be bounded to 'lua lifetime
@@ -812,7 +812,7 @@ impl<'lua, T> UserDataMethods<'lua, T> for NonStaticUserDataRegistry<'lua, T> {
     where
         F: Fn(&'lua Lua, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
+        R: IntoLuaMulti,
     {
         let func_name = format!("{}.{}", short_type_name::<T>(), name.as_ref());
         let func = NonStaticMethod::Function(Box::new(move |lua, nargs| unsafe {
@@ -826,7 +826,7 @@ impl<'lua, T> UserDataMethods<'lua, T> for NonStaticUserDataRegistry<'lua, T> {
     where
         F: FnMut(&'lua Lua, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
+        R: IntoLuaMulti,
     {
         let func_name = format!("{}.{}", short_type_name::<T>(), name.as_ref());
         let func = NonStaticMethod::FunctionMut(Box::new(move |lua, nargs| unsafe {
@@ -842,7 +842,7 @@ impl<'lua, T> UserDataMethods<'lua, T> for NonStaticUserDataRegistry<'lua, T> {
         F: Fn(&'lua Lua, A) -> FR + MaybeSend + 'static,
         A: FromLuaMulti<'lua>,
         FR: Future<Output = Result<R>> + 'lua,
-        R: IntoLuaMulti<'lua>,
+        R: IntoLuaMulti,
     {
         // The panic should never happen as async non-static code wouldn't compile
         // Non-static lifetime must be bounded to 'lua lifetime
@@ -853,7 +853,7 @@ impl<'lua, T> UserDataMethods<'lua, T> for NonStaticUserDataRegistry<'lua, T> {
     where
         M: Fn(&'lua Lua, &T, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
+        R: IntoLuaMulti,
     {
         let func_name = format!("{}.{}", short_type_name::<T>(), name.as_ref());
         let method = NonStaticMethod::Method(Box::new(move |lua, ud, nargs| unsafe {
@@ -867,7 +867,7 @@ impl<'lua, T> UserDataMethods<'lua, T> for NonStaticUserDataRegistry<'lua, T> {
     where
         M: FnMut(&'lua Lua, &mut T, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
+        R: IntoLuaMulti,
     {
         let func_name = format!("{}.{}", short_type_name::<T>(), name.as_ref());
         let method = NonStaticMethod::MethodMut(Box::new(move |lua, ud, nargs| unsafe {
@@ -885,7 +885,7 @@ impl<'lua, T> UserDataMethods<'lua, T> for NonStaticUserDataRegistry<'lua, T> {
         M: Fn(&'lua Lua, &'s T, A) -> MR + MaybeSend + 'static,
         A: FromLuaMulti<'lua>,
         MR: Future<Output = Result<R>> + 's,
-        R: IntoLuaMulti<'lua>,
+        R: IntoLuaMulti,
     {
         // The panic should never happen as async non-static code wouldn't compile
         // Non-static lifetime must be bounded to 'lua lifetime
@@ -900,7 +900,7 @@ impl<'lua, T> UserDataMethods<'lua, T> for NonStaticUserDataRegistry<'lua, T> {
         M: Fn(&'lua Lua, &'s mut T, A) -> MR + MaybeSend + 'static,
         A: FromLuaMulti<'lua>,
         MR: Future<Output = Result<R>> + 's,
-        R: IntoLuaMulti<'lua>,
+        R: IntoLuaMulti,
     {
         // The panic should never happen as async non-static code wouldn't compile
         // Non-static lifetime must be bounded to 'lua lifetime
@@ -911,7 +911,7 @@ impl<'lua, T> UserDataMethods<'lua, T> for NonStaticUserDataRegistry<'lua, T> {
     where
         F: Fn(&'lua Lua, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
+        R: IntoLuaMulti,
     {
         let func_name = format!("{}.{}", short_type_name::<T>(), name.as_ref());
         let func = NonStaticMethod::Function(Box::new(move |lua, nargs| unsafe {
@@ -925,7 +925,7 @@ impl<'lua, T> UserDataMethods<'lua, T> for NonStaticUserDataRegistry<'lua, T> {
     where
         F: FnMut(&'lua Lua, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
+        R: IntoLuaMulti,
     {
         let func_name = format!("{}.{}", short_type_name::<T>(), name.as_ref());
         let func = NonStaticMethod::FunctionMut(Box::new(move |lua, nargs| unsafe {
@@ -941,7 +941,7 @@ impl<'lua, T> UserDataMethods<'lua, T> for NonStaticUserDataRegistry<'lua, T> {
         F: Fn(&'lua Lua, A) -> FR + MaybeSend + 'static,
         A: FromLuaMulti<'lua>,
         FR: Future<Output = Result<R>> + 'lua,
-        R: IntoLuaMulti<'lua>,
+        R: IntoLuaMulti,
     {
         // The panic should never happen as async non-static code wouldn't compile
         // Non-static lifetime must be bounded to 'lua lifetime

src/serde/de.rs

@@ -1,5 +1,4 @@
 use std::cell::RefCell;
-use std::convert::TryInto;
 use std::os::raw::c_void;
 use std::rc::Rc;
 use std::result::Result as StdResult;
@@ -15,8 +14,8 @@ use crate::value::Value;
 
 /// A struct for deserializing Lua values into Rust values.
 #[derive(Debug)]
-pub struct Deserializer<'lua> {
-    value: Value<'lua>,
+pub struct Deserializer {
+    value: Value,
     options: Options,
     visited: Rc<RefCell<FxHashSet<*const c_void>>>,
 }
@@ -52,7 +51,7 @@ pub struct Options {
 
 impl Default for Options {
     fn default() -> Self {
-        Self::new()
+        const { Self::new() }
     }
 }
 
@@ -94,14 +93,14 @@ impl Options {
     }
 }
 
-impl<'lua> Deserializer<'lua> {
+impl Deserializer {
     /// Creates a new Lua Deserializer for the `Value`.
-    pub fn new(value: Value<'lua>) -> Self {
+    pub fn new(value: Value) -> Self {
         Self::new_with_options(value, Options::default())
     }
 
     /// Creates a new Lua Deserializer for the `Value` with custom options.
-    pub fn new_with_options(value: Value<'lua>, options: Options) -> Self {
+    pub fn new_with_options(value: Value, options: Options) -> Self {
         Deserializer {
             value,
             options,
@@ -109,11 +108,7 @@ impl<'lua> Deserializer<'lua> {
         }
     }
 
-    fn from_parts(
-        value: Value<'lua>,
-        options: Options,
-        visited: Rc<RefCell<FxHashSet<*const c_void>>>,
-    ) -> Self {
+    fn from_parts(value: Value, options: Options, visited: Rc<RefCell<FxHashSet<*const c_void>>>) -> Self {
         Deserializer {
             value,
             options,
@@ -122,7 +117,7 @@ impl<'lua> Deserializer<'lua> {
     }
 }
 
-impl<'lua, 'de> serde::Deserializer<'de> for Deserializer<'lua> {
+impl<'de> serde::Deserializer<'de> for Deserializer {
     type Error = Error;
 
     #[inline]
@@ -134,16 +129,14 @@ impl<'lua, 'de> serde::Deserializer<'de> for Deserializer<'lua> {
             Value::Nil => visitor.visit_unit(),
             Value::Boolean(b) => visitor.visit_bool(b),
             #[allow(clippy::useless_conversion)]
-            Value::Integer(i) => {
-                visitor.visit_i64(i.try_into().expect("cannot convert lua_Integer to i64"))
-            }
+            Value::Integer(i) => visitor.visit_i64(i.into()),
             #[allow(clippy::useless_conversion)]
             Value::Number(n) => visitor.visit_f64(n.into()),
             #[cfg(feature = "luau")]
             Value::Vector(_) => self.deserialize_seq(visitor),
             Value::String(s) => match s.to_str() {
-                Ok(s) => visitor.visit_str(s),
-                Err(_) => visitor.visit_bytes(s.as_bytes()),
+                Ok(s) => visitor.visit_str(&s),
+                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(_) => self.deserialize_map(visitor),
@@ -151,6 +144,15 @@ impl<'lua, 'de> serde::Deserializer<'de> for Deserializer<'lua> {
             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::Function(_)
             | Value::Thread(_)
             | Value::UserData(_)
@@ -261,10 +263,7 @@ impl<'lua, 'de> serde::Deserializer<'de> for Deserializer<'lua> {
                 if deserializer.seq.count() == 0 {
                     Ok(seq)
                 } else {
-                    Err(de::Error::invalid_length(
-                        len,
-                        &"fewer elements in the table",
-                    ))
+                    Err(de::Error::invalid_length(len, &"fewer elements in the table"))
                 }
             }
             Value::UserData(ud) if ud.is_serializable() => {
@@ -286,12 +285,7 @@ impl<'lua, 'de> serde::Deserializer<'de> for Deserializer<'lua> {
     }
 
     #[inline]
-    fn deserialize_tuple_struct<V>(
-        self,
-        _name: &'static str,
-        _len: usize,
-        visitor: V,
-    ) -> Result<V::Value>
+    fn deserialize_tuple_struct<V>(self, _name: &'static str, _len: usize, visitor: V) -> Result<V::Value>
     where
         V: de::Visitor<'de>,
     {
@@ -308,7 +302,7 @@ impl<'lua, 'de> serde::Deserializer<'de> for Deserializer<'lua> {
                 let _guard = RecursionGuard::new(&t, &self.visited);
 
                 let mut deserializer = MapDeserializer {
-                    pairs: MapPairs::new(t, self.options.sort_keys)?,
+                    pairs: MapPairs::new(&t, self.options.sort_keys)?,
                     value: None,
                     options: self.options,
                     visited: self.visited,
@@ -389,13 +383,13 @@ impl<'lua, 'de> serde::Deserializer<'de> for Deserializer<'lua> {
     }
 }
 
-struct SeqDeserializer<'lua> {
-    seq: TableSequence<'lua, Value<'lua>>,
+struct SeqDeserializer<'a> {
+    seq: TableSequence<'a, Value>,
     options: Options,
     visited: Rc<RefCell<FxHashSet<*const c_void>>>,
 }
 
-impl<'lua, 'de> de::SeqAccess<'de> for SeqDeserializer<'lua> {
+impl<'de> de::SeqAccess<'de> for SeqDeserializer<'_> {
     type Error = Error;
 
     fn next_element_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>>
@@ -448,8 +442,7 @@ impl<'de> de::SeqAccess<'de> for VecDeserializer {
             Some(&n) => {
                 self.next += 1;
                 let visited = Rc::clone(&self.visited);
-                let deserializer =
-                    Deserializer::from_parts(Value::Number(n as _), self.options, visited);
+                let deserializer = Deserializer::from_parts(Value::Number(n as _), self.options, visited);
                 seed.deserialize(deserializer).map(Some)
             }
             None => Ok(None),
@@ -461,13 +454,13 @@ impl<'de> de::SeqAccess<'de> for VecDeserializer {
     }
 }
 
-pub(crate) enum MapPairs<'lua> {
-    Iter(TablePairs<'lua, Value<'lua>, Value<'lua>>),
-    Vec(Vec<(Value<'lua>, Value<'lua>)>),
+pub(crate) enum MapPairs<'a> {
+    Iter(TablePairs<'a, Value, Value>),
+    Vec(Vec<(Value, Value)>),
 }
 
-impl<'lua> MapPairs<'lua> {
-    pub(crate) fn new(t: Table<'lua>, sort_keys: bool) -> Result<Self> {
+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
@@ -492,8 +485,8 @@ impl<'lua> MapPairs<'lua> {
     }
 }
 
-impl<'lua> Iterator for MapPairs<'lua> {
-    type Item = Result<(Value<'lua>, Value<'lua>)>;
+impl Iterator for MapPairs<'_> {
+    type Item = Result<(Value, Value)>;
 
     fn next(&mut self) -> Option<Self::Item> {
         match self {
@@ -503,21 +496,16 @@ impl<'lua> Iterator for MapPairs<'lua> {
     }
 }
 
-struct MapDeserializer<'lua> {
-    pairs: MapPairs<'lua>,
-    value: Option<Value<'lua>>,
+struct MapDeserializer<'a> {
+    pairs: MapPairs<'a>,
+    value: Option<Value>,
     options: Options,
     visited: Rc<RefCell<FxHashSet<*const c_void>>>,
     processed: usize,
 }
 
-impl<'lua, 'de> de::MapAccess<'de> for MapDeserializer<'lua> {
-    type Error = Error;
-
-    fn next_key_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>>
-    where
-        T: de::DeserializeSeed<'de>,
-    {
+impl<'a> MapDeserializer<'a> {
+    fn next_key_deserializer(&mut self) -> Result<Option<Deserializer>> {
         loop {
             match self.pairs.next() {
                 Some(item) => {
@@ -533,23 +521,45 @@ impl<'lua, 'de> de::MapAccess<'de> for MapDeserializer<'lua> {
                     self.value = Some(value);
                     let visited = Rc::clone(&self.visited);
                     let key_de = Deserializer::from_parts(key, self.options, visited);
-                    return seed.deserialize(key_de).map(Some);
+                    return Ok(Some(key_de));
                 }
                 None => return Ok(None),
             }
         }
     }
 
+    fn next_value_deserializer(&mut self) -> Result<Deserializer> {
+        match self.value.take() {
+            Some(value) => {
+                let visited = Rc::clone(&self.visited);
+                Ok(Deserializer::from_parts(value, self.options, visited))
+            }
+            None => Err(de::Error::custom("value is missing")),
+        }
+    }
+}
+
+impl<'de> de::MapAccess<'de> for MapDeserializer<'_> {
+    type Error = Error;
+
+    fn next_key_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>>
+    where
+        T: de::DeserializeSeed<'de>,
+    {
+        match self.next_key_deserializer() {
+            Ok(Some(key_de)) => seed.deserialize(key_de).map(Some),
+            Ok(None) => Ok(None),
+            Err(error) => Err(error),
+        }
+    }
+
     fn next_value_seed<T>(&mut self, seed: T) -> Result<T::Value>
     where
         T: de::DeserializeSeed<'de>,
     {
-        match self.value.take() {
-            Some(value) => {
-                let visited = Rc::clone(&self.visited);
-                seed.deserialize(Deserializer::from_parts(value, self.options, visited))
-            }
-            None => Err(de::Error::custom("value is missing")),
+        match self.next_value_deserializer() {
+            Ok(value_de) => seed.deserialize(value_de),
+            Err(error) => Err(error),
         }
     }
 
@@ -561,16 +571,16 @@ impl<'lua, 'de> de::MapAccess<'de> for MapDeserializer<'lua> {
     }
 }
 
-struct EnumDeserializer<'lua> {
+struct EnumDeserializer {
     variant: StdString,
-    value: Option<Value<'lua>>,
+    value: Option<Value>,
     options: Options,
     visited: Rc<RefCell<FxHashSet<*const c_void>>>,
 }
 
-impl<'lua, 'de> de::EnumAccess<'de> for EnumDeserializer<'lua> {
+impl<'de> de::EnumAccess<'de> for EnumDeserializer {
     type Error = Error;
-    type Variant = VariantDeserializer<'lua>;
+    type Variant = VariantDeserializer;
 
     fn variant_seed<T>(self, seed: T) -> Result<(T::Value, Self::Variant)>
     where
@@ -586,13 +596,13 @@ impl<'lua, 'de> de::EnumAccess<'de> for EnumDeserializer<'lua> {
     }
 }
 
-struct VariantDeserializer<'lua> {
-    value: Option<Value<'lua>>,
+struct VariantDeserializer {
+    value: Option<Value>,
     options: Options,
     visited: Rc<RefCell<FxHashSet<*const c_void>>>,
 }
 
-impl<'lua, 'de> de::VariantAccess<'de> for VariantDeserializer<'lua> {
+impl<'de> de::VariantAccess<'de> for VariantDeserializer {
     type Error = Error;
 
     fn unit_variant(self) -> Result<()> {
@@ -610,9 +620,7 @@ impl<'lua, 'de> de::VariantAccess<'de> for VariantDeserializer<'lua> {
         T: de::DeserializeSeed<'de>,
     {
         match self.value {
-            Some(value) => {
-                seed.deserialize(Deserializer::from_parts(value, self.options, self.visited))
-            }
+            Some(value) => seed.deserialize(Deserializer::from_parts(value, self.options, self.visited)),
             None => Err(de::Error::invalid_type(
                 de::Unexpected::UnitVariant,
                 &"newtype variant",
@@ -655,14 +663,14 @@ impl<'lua, 'de> de::VariantAccess<'de> for VariantDeserializer<'lua> {
 
 // Adds `ptr` to the `visited` map and removes on drop
 // Used to track recursive tables but allow to traverse same tables multiple times
-struct RecursionGuard {
+pub(crate) struct RecursionGuard {
     ptr: *const c_void,
     visited: Rc<RefCell<FxHashSet<*const c_void>>>,
 }
 
 impl RecursionGuard {
     #[inline]
-    fn new(table: &Table, visited: &Rc<RefCell<FxHashSet<*const c_void>>>) -> Self {
+    pub(crate) fn new(table: &Table, visited: &Rc<RefCell<FxHashSet<*const c_void>>>) -> Self {
         let visited = Rc::clone(visited);
         let ptr = table.to_pointer();
         visited.borrow_mut().insert(ptr);
@@ -711,6 +719,11 @@ fn serde_userdata<V>(
     ud: AnyUserData,
     f: impl FnOnce(serde_value::Value) -> std::result::Result<V, serde_value::DeserializerError>,
 ) -> Result<V> {
-    let value = serde_value::to_value(ud).map_err(|err| Error::SerializeError(err.to_string()))?;
-    f(value).map_err(|err| Error::DeserializeError(err.to_string()))
+    match serde_value::to_value(ud) {
+        Ok(value) => match f(value) {
+            Ok(r) => Ok(r),
+            Err(error) => Err(Error::DeserializeError(error.to_string())),
+        },
+        Err(error) => Err(Error::SerializeError(error.to_string())),
+    }
 }

src/serde/mod.rs

@@ -2,11 +2,12 @@
 
 use std::os::raw::c_void;
 
-use serde::{de::DeserializeOwned, ser::Serialize};
+use serde::de::DeserializeOwned;
+use serde::ser::Serialize;
 
 use crate::error::Result;
-use crate::lua::Lua;
 use crate::private::Sealed;
+use crate::state::Lua;
 use crate::table::Table;
 use crate::util::check_stack;
 use crate::value::Value;
@@ -99,7 +100,7 @@ pub trait LuaSerdeExt: Sealed {
     ///     "#).exec()
     /// }
     /// ```
-    fn to_value<'lua, T: Serialize + ?Sized>(&'lua self, t: &T) -> Result<Value<'lua>>;
+    fn to_value<T: Serialize + ?Sized>(&self, t: &T) -> Result<Value>;
 
     /// Converts `T` into a [`Value`] instance with options.
     ///
@@ -124,7 +125,7 @@ pub trait LuaSerdeExt: Sealed {
     ///     "#).exec()
     /// }
     /// ```
-    fn to_value_with<'lua, T>(&'lua self, t: &T, options: ser::Options) -> Result<Value<'lua>>
+    fn to_value_with<T>(&self, t: &T, options: ser::Options) -> Result<Value>
     where
         T: Serialize + ?Sized;
 
@@ -189,8 +190,7 @@ pub trait LuaSerdeExt: Sealed {
     /// }
     /// ```
     #[allow(clippy::wrong_self_convention)]
-    fn from_value_with<T: DeserializeOwned>(&self, value: Value, options: de::Options)
-        -> Result<T>;
+    fn from_value_with<T: DeserializeOwned>(&self, value: Value, options: de::Options) -> Result<T>;
 }
 
 impl LuaSerdeExt for Lua {
@@ -199,20 +199,21 @@ impl LuaSerdeExt for Lua {
     }
 
     fn array_metatable(&self) -> Table {
+        let lua = self.lock();
         unsafe {
-            push_array_metatable(self.ref_thread());
-            Table(self.pop_ref_thread())
+            push_array_metatable(lua.ref_thread());
+            Table(lua.pop_ref_thread())
         }
     }
 
-    fn to_value<'lua, T>(&'lua self, t: &T) -> Result<Value<'lua>>
+    fn to_value<T>(&self, t: &T) -> Result<Value>
     where
         T: Serialize + ?Sized,
     {
         t.serialize(ser::Serializer::new(self))
     }
 
-    fn to_value_with<'lua, T>(&'lua self, t: &T, options: ser::Options) -> Result<Value<'lua>>
+    fn to_value_with<T>(&self, t: &T, options: ser::Options) -> Result<Value>
     where
         T: Serialize + ?Sized,
     {

src/serde/ser.rs

@@ -2,15 +2,14 @@ use serde::{ser, Serialize};
 
 use super::LuaSerdeExt;
 use crate::error::{Error, Result};
-use crate::lua::Lua;
-use crate::string::String;
+use crate::state::Lua;
 use crate::table::Table;
 use crate::value::{IntoLua, Value};
 
 /// A struct for serializing Rust values into Lua values.
 #[derive(Debug)]
-pub struct Serializer<'lua> {
-    lua: &'lua Lua,
+pub struct Serializer<'a> {
+    lua: &'a Lua,
     options: Options,
 }
 
@@ -43,11 +42,17 @@ pub struct Options {
     /// [`null`]: crate::LuaSerdeExt::null
     /// [`Nil`]: crate::Value::Nil
     pub serialize_unit_to_null: bool,
+
+    /// If true, serialize `serde_json::Number` with arbitrary_precision to a Lua number.
+    /// Otherwise it will be serialized as an object (what serde does).
+    ///
+    /// Default: **false**
+    pub detect_serde_json_arbitrary_precision: bool,
 }
 
 impl Default for Options {
     fn default() -> Self {
-        Self::new()
+        const { Self::new() }
     }
 }
 
@@ -58,6 +63,7 @@ impl Options {
             set_array_metatable: true,
             serialize_none_to_null: true,
             serialize_unit_to_null: true,
+            detect_serde_json_arbitrary_precision: false,
         }
     }
 
@@ -87,16 +93,30 @@ impl Options {
         self.serialize_unit_to_null = enabled;
         self
     }
+
+    /// Sets [`detect_serde_json_arbitrary_precision`] option.
+    ///
+    /// This option is used to serialize `serde_json::Number` with arbitrary precision to a Lua
+    /// number. Otherwise it will be serialized as an object (what serde does).
+    ///
+    /// This option is disabled by default.
+    ///
+    /// [`detect_serde_json_arbitrary_precision`]: #structfield.detect_serde_json_arbitrary_precision
+    #[must_use]
+    pub const fn detect_serde_json_arbitrary_precision(mut self, enabled: bool) -> Self {
+        self.detect_serde_json_arbitrary_precision = enabled;
+        self
+    }
 }
 
-impl<'lua> Serializer<'lua> {
+impl<'a> Serializer<'a> {
     /// Creates a new Lua Serializer with default options.
-    pub fn new(lua: &'lua Lua) -> Self {
+    pub fn new(lua: &'a Lua) -> Self {
         Self::new_with_options(lua, Options::default())
     }
 
     /// Creates a new Lua Serializer with custom options.
-    pub fn new_with_options(lua: &'lua Lua, options: Options) -> Self {
+    pub fn new_with_options(lua: &'a Lua, options: Options) -> Self {
         Serializer { lua, options }
     }
 }
@@ -104,28 +124,28 @@ impl<'lua> Serializer<'lua> {
 macro_rules! lua_serialize_number {
     ($name:ident, $t:ty) => {
         #[inline]
-        fn $name(self, value: $t) -> Result<Value<'lua>> {
+        fn $name(self, value: $t) -> Result<Value> {
             value.into_lua(self.lua)
         }
     };
 }
 
-impl<'lua> ser::Serializer for Serializer<'lua> {
-    type Ok = Value<'lua>;
+impl<'a> ser::Serializer for Serializer<'a> {
+    type Ok = Value;
     type Error = Error;
 
     // Associated types for keeping track of additional state while serializing
     // compound data structures like sequences and maps.
-    type SerializeSeq = SerializeSeq<'lua>;
-    type SerializeTuple = SerializeSeq<'lua>;
-    type SerializeTupleStruct = SerializeSeq<'lua>;
-    type SerializeTupleVariant = SerializeTupleVariant<'lua>;
-    type SerializeMap = SerializeMap<'lua>;
-    type SerializeStruct = SerializeMap<'lua>;
-    type SerializeStructVariant = SerializeStructVariant<'lua>;
+    type SerializeSeq = SerializeSeq<'a>;
+    type SerializeTuple = SerializeSeq<'a>;
+    type SerializeTupleStruct = SerializeSeq<'a>;
+    type SerializeTupleVariant = SerializeTupleVariant<'a>;
+    type SerializeMap = SerializeMap<'a>;
+    type SerializeStruct = SerializeStruct<'a>;
+    type SerializeStructVariant = SerializeStructVariant<'a>;
 
     #[inline]
-    fn serialize_bool(self, value: bool) -> Result<Value<'lua>> {
+    fn serialize_bool(self, value: bool) -> Result<Value> {
         Ok(Value::Boolean(value))
     }
 
@@ -144,22 +164,22 @@ impl<'lua> ser::Serializer for Serializer<'lua> {
     lua_serialize_number!(serialize_f64, f64);
 
     #[inline]
-    fn serialize_char(self, value: char) -> Result<Value<'lua>> {
+    fn serialize_char(self, value: char) -> Result<Value> {
         self.serialize_str(&value.to_string())
     }
 
     #[inline]
-    fn serialize_str(self, value: &str) -> Result<Value<'lua>> {
+    fn serialize_str(self, value: &str) -> Result<Value> {
         self.lua.create_string(value).map(Value::String)
     }
 
     #[inline]
-    fn serialize_bytes(self, value: &[u8]) -> Result<Value<'lua>> {
+    fn serialize_bytes(self, value: &[u8]) -> Result<Value> {
         self.lua.create_string(value).map(Value::String)
     }
 
     #[inline]
-    fn serialize_none(self) -> Result<Value<'lua>> {
+    fn serialize_none(self) -> Result<Value> {
         if self.options.serialize_none_to_null {
             Ok(self.lua.null())
         } else {
@@ -168,7 +188,7 @@ impl<'lua> ser::Serializer for Serializer<'lua> {
     }
 
     #[inline]
-    fn serialize_some<T>(self, value: &T) -> Result<Value<'lua>>
+    fn serialize_some<T>(self, value: &T) -> Result<Value>
     where
         T: Serialize + ?Sized,
     {
@@ -176,7 +196,7 @@ impl<'lua> ser::Serializer for Serializer<'lua> {
     }
 
     #[inline]
-    fn serialize_unit(self) -> Result<Value<'lua>> {
+    fn serialize_unit(self) -> Result<Value> {
         if self.options.serialize_unit_to_null {
             Ok(self.lua.null())
         } else {
@@ -185,7 +205,7 @@ impl<'lua> ser::Serializer for Serializer<'lua> {
     }
 
     #[inline]
-    fn serialize_unit_struct(self, _name: &'static str) -> Result<Value<'lua>> {
+    fn serialize_unit_struct(self, _name: &'static str) -> Result<Value> {
         if self.options.serialize_unit_to_null {
             Ok(self.lua.null())
         } else {
@@ -199,12 +219,12 @@ impl<'lua> ser::Serializer for Serializer<'lua> {
         _name: &'static str,
         _variant_index: u32,
         variant: &'static str,
-    ) -> Result<Value<'lua>> {
+    ) -> Result<Value> {
         self.serialize_str(variant)
     }
 
     #[inline]
-    fn serialize_newtype_struct<T>(self, _name: &'static str, value: &T) -> Result<Value<'lua>>
+    fn serialize_newtype_struct<T>(self, _name: &'static str, value: &T) -> Result<Value>
     where
         T: Serialize + ?Sized,
     {
@@ -218,7 +238,7 @@ impl<'lua> ser::Serializer for Serializer<'lua> {
         _variant_index: u32,
         variant: &'static str,
         value: &T,
-    ) -> Result<Value<'lua>>
+    ) -> Result<Value>
     where
         T: Serialize + ?Sized,
     {
@@ -235,7 +255,7 @@ impl<'lua> ser::Serializer for Serializer<'lua> {
         if self.options.set_array_metatable {
             table.set_metatable(Some(self.lua.array_metatable()));
         }
-        Ok(SerializeSeq::new(table, self.options))
+        Ok(SerializeSeq::new(self.lua, table, self.options))
     }
 
     #[inline]
@@ -244,11 +264,7 @@ impl<'lua> ser::Serializer for Serializer<'lua> {
     }
 
     #[inline]
-    fn serialize_tuple_struct(
-        self,
-        name: &'static str,
-        len: usize,
-    ) -> Result<Self::SerializeTupleStruct> {
+    fn serialize_tuple_struct(self, name: &'static str, len: usize) -> Result<Self::SerializeTupleStruct> {
         #[cfg(feature = "luau")]
         if name == "Vector" && len == crate::types::Vector::SIZE {
             return Ok(SerializeSeq::new_vector(self.lua, self.options));
@@ -266,7 +282,8 @@ impl<'lua> ser::Serializer for Serializer<'lua> {
         _len: usize,
     ) -> Result<Self::SerializeTupleVariant> {
         Ok(SerializeTupleVariant {
-            name: self.lua.create_string(variant)?,
+            lua: self.lua,
+            variant,
             table: self.lua.create_table()?,
             options: self.options,
         })
@@ -275,6 +292,7 @@ impl<'lua> ser::Serializer for Serializer<'lua> {
     #[inline]
     fn serialize_map(self, len: Option<usize>) -> Result<Self::SerializeMap> {
         Ok(SerializeMap {
+            lua: self.lua,
             key: None,
             table: self.lua.create_table_with_capacity(0, len.unwrap_or(0))?,
             options: self.options,
@@ -282,8 +300,23 @@ impl<'lua> ser::Serializer for Serializer<'lua> {
     }
 
     #[inline]
-    fn serialize_struct(self, _name: &'static str, len: usize) -> Result<Self::SerializeStruct> {
-        self.serialize_map(Some(len))
+    fn serialize_struct(self, name: &'static str, len: usize) -> Result<Self::SerializeStruct> {
+        if self.options.detect_serde_json_arbitrary_precision
+            && name == "$serde_json::private::Number"
+            && len == 1
+        {
+            return Ok(SerializeStruct {
+                lua: self.lua,
+                inner: None,
+                options: self.options,
+            });
+        }
+
+        Ok(SerializeStruct {
+            lua: self.lua,
+            inner: Some(Value::Table(self.lua.create_table_with_capacity(0, len)?)),
+            options: self.options,
+        })
     }
 
     #[inline]
@@ -295,7 +328,8 @@ impl<'lua> ser::Serializer for Serializer<'lua> {
         len: usize,
     ) -> Result<Self::SerializeStructVariant> {
         Ok(SerializeStructVariant {
-            name: self.lua.create_string(variant)?,
+            lua: self.lua,
+            variant,
             table: self.lua.create_table_with_capacity(0, len)?,
             options: self.options,
         })
@@ -303,19 +337,19 @@ impl<'lua> ser::Serializer for Serializer<'lua> {
 }
 
 #[doc(hidden)]
-pub struct SerializeSeq<'lua> {
-    lua: &'lua Lua,
+pub struct SerializeSeq<'a> {
+    lua: &'a Lua,
     #[cfg(feature = "luau")]
     vector: Option<crate::types::Vector>,
-    table: Option<Table<'lua>>,
+    table: Option<Table>,
     next: usize,
     options: Options,
 }
 
-impl<'lua> SerializeSeq<'lua> {
-    const fn new(table: Table<'lua>, options: Options) -> Self {
+impl<'a> SerializeSeq<'a> {
+    fn new(lua: &'a Lua, table: Table, options: Options) -> Self {
         Self {
-            lua: table.0.lua,
+            lua,
             #[cfg(feature = "luau")]
             vector: None,
             table: Some(table),
@@ -325,7 +359,7 @@ impl<'lua> SerializeSeq<'lua> {
     }
 
     #[cfg(feature = "luau")]
-    const fn new_vector(lua: &'lua Lua, options: Options) -> Self {
+    const fn new_vector(lua: &'a Lua, options: Options) -> Self {
         Self {
             lua,
             vector: Some(crate::types::Vector::zero()),
@@ -336,8 +370,8 @@ impl<'lua> SerializeSeq<'lua> {
     }
 }
 
-impl<'lua> ser::SerializeSeq for SerializeSeq<'lua> {
-    type Ok = Value<'lua>;
+impl ser::SerializeSeq for SerializeSeq<'_> {
+    type Ok = Value;
     type Error = Error;
 
     fn serialize_element<T>(&mut self, value: &T) -> Result<()>
@@ -351,13 +385,13 @@ impl<'lua> ser::SerializeSeq for SerializeSeq<'lua> {
         Ok(())
     }
 
-    fn end(self) -> Result<Value<'lua>> {
+    fn end(self) -> Result<Value> {
         Ok(Value::Table(self.table.unwrap()))
     }
 }
 
-impl<'lua> ser::SerializeTuple for SerializeSeq<'lua> {
-    type Ok = Value<'lua>;
+impl ser::SerializeTuple for SerializeSeq<'_> {
+    type Ok = Value;
     type Error = Error;
 
     fn serialize_element<T>(&mut self, value: &T) -> Result<()>
@@ -367,13 +401,13 @@ impl<'lua> ser::SerializeTuple for SerializeSeq<'lua> {
         ser::SerializeSeq::serialize_element(self, value)
     }
 
-    fn end(self) -> Result<Value<'lua>> {
+    fn end(self) -> Result<Value> {
         ser::SerializeSeq::end(self)
     }
 }
 
-impl<'lua> ser::SerializeTupleStruct for SerializeSeq<'lua> {
-    type Ok = Value<'lua>;
+impl ser::SerializeTupleStruct for SerializeSeq<'_> {
+    type Ok = Value;
     type Error = Error;
 
     fn serialize_field<T>(&mut self, value: &T) -> Result<()>
@@ -391,7 +425,7 @@ impl<'lua> ser::SerializeTupleStruct for SerializeSeq<'lua> {
         ser::SerializeSeq::serialize_element(self, value)
     }
 
-    fn end(self) -> Result<Value<'lua>> {
+    fn end(self) -> Result<Value> {
         #[cfg(feature = "luau")]
         if let Some(vector) = self.vector {
             return Ok(Value::Vector(vector));
@@ -401,49 +435,48 @@ impl<'lua> ser::SerializeTupleStruct for SerializeSeq<'lua> {
 }
 
 #[doc(hidden)]
-pub struct SerializeTupleVariant<'lua> {
-    name: String<'lua>,
-    table: Table<'lua>,
+pub struct SerializeTupleVariant<'a> {
+    lua: &'a Lua,
+    variant: &'static str,
+    table: Table,
     options: Options,
 }
 
-impl<'lua> ser::SerializeTupleVariant for SerializeTupleVariant<'lua> {
-    type Ok = Value<'lua>;
+impl ser::SerializeTupleVariant for SerializeTupleVariant<'_> {
+    type Ok = Value;
     type Error = Error;
 
     fn serialize_field<T>(&mut self, value: &T) -> Result<()>
     where
         T: Serialize + ?Sized,
     {
-        let lua = self.table.0.lua;
-        self.table.raw_push(lua.to_value_with(value, self.options)?)
+        self.table.raw_push(self.lua.to_value_with(value, self.options)?)
     }
 
-    fn end(self) -> Result<Value<'lua>> {
-        let lua = self.table.0.lua;
-        let table = lua.create_table()?;
-        table.raw_set(self.name, self.table)?;
+    fn end(self) -> Result<Value> {
+        let table = self.lua.create_table()?;
+        table.raw_set(self.variant, self.table)?;
         Ok(Value::Table(table))
     }
 }
 
 #[doc(hidden)]
-pub struct SerializeMap<'lua> {
-    table: Table<'lua>,
-    key: Option<Value<'lua>>,
+pub struct SerializeMap<'a> {
+    lua: &'a Lua,
+    table: Table,
+    key: Option<Value>,
     options: Options,
 }
 
-impl<'lua> ser::SerializeMap for SerializeMap<'lua> {
-    type Ok = Value<'lua>;
+impl ser::SerializeMap for SerializeMap<'_> {
+    type Ok = Value;
     type Error = Error;
 
     fn serialize_key<T>(&mut self, key: &T) -> Result<()>
     where
         T: Serialize + ?Sized,
     {
-        let lua = self.table.0.lua;
-        self.key = Some(lua.to_value_with(key, self.options)?);
+        self.key = Some(self.lua.to_value_with(key, self.options)?);
         Ok(())
     }
 
@@ -451,62 +484,90 @@ impl<'lua> ser::SerializeMap for SerializeMap<'lua> {
     where
         T: Serialize + ?Sized,
     {
-        let lua = self.table.0.lua;
-        let key = mlua_expect!(
-            self.key.take(),
-            "serialize_value called before serialize_key"
-        );
-        let value = lua.to_value_with(value, self.options)?;
+        let key = mlua_expect!(self.key.take(), "serialize_value called before serialize_key");
+        let value = self.lua.to_value_with(value, self.options)?;
         self.table.raw_set(key, value)
     }
 
-    fn end(self) -> Result<Value<'lua>> {
+    fn end(self) -> Result<Value> {
         Ok(Value::Table(self.table))
     }
 }
 
-impl<'lua> ser::SerializeStruct for SerializeMap<'lua> {
-    type Ok = Value<'lua>;
+#[doc(hidden)]
+pub struct SerializeStruct<'a> {
+    lua: &'a Lua,
+    inner: Option<Value>,
+    options: Options,
+}
+
+impl ser::SerializeStruct for SerializeStruct<'_> {
+    type Ok = Value;
     type Error = Error;
 
     fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<()>
     where
         T: Serialize + ?Sized,
     {
-        ser::SerializeMap::serialize_key(self, key)?;
-        ser::SerializeMap::serialize_value(self, value)
+        match self.inner {
+            Some(Value::Table(ref table)) => {
+                table.raw_set(key, self.lua.to_value_with(value, self.options)?)?;
+            }
+            None if self.options.detect_serde_json_arbitrary_precision => {
+                // A special case for `serde_json::Number` with arbitrary precision.
+                assert_eq!(key, "$serde_json::private::Number");
+                self.inner = Some(self.lua.to_value_with(value, self.options)?);
+            }
+            _ => unreachable!(),
+        }
+        Ok(())
     }
 
-    fn end(self) -> Result<Value<'lua>> {
-        ser::SerializeMap::end(self)
+    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");
+                if number_s.contains(['.', 'e', 'E']) {
+                    if let Ok(number) = number_s.parse().map(Value::Number) {
+                        return Ok(number);
+                    }
+                }
+                Ok(number_s
+                    .parse()
+                    .map(Value::Integer)
+                    .or_else(|_| number_s.parse().map(Value::Number))
+                    .unwrap_or(value))
+            }
+            _ => unreachable!(),
+        }
     }
 }
 
 #[doc(hidden)]
-pub struct SerializeStructVariant<'lua> {
-    name: String<'lua>,
-    table: Table<'lua>,
+pub struct SerializeStructVariant<'a> {
+    lua: &'a Lua,
+    variant: &'static str,
+    table: Table,
     options: Options,
 }
 
-impl<'lua> ser::SerializeStructVariant for SerializeStructVariant<'lua> {
-    type Ok = Value<'lua>;
+impl ser::SerializeStructVariant for SerializeStructVariant<'_> {
+    type Ok = Value;
     type Error = Error;
 
     fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<()>
     where
         T: Serialize + ?Sized,
     {
-        let lua = self.table.0.lua;
         self.table
-            .raw_set(key, lua.to_value_with(value, self.options)?)?;
+            .raw_set(key, self.lua.to_value_with(value, self.options)?)?;
         Ok(())
     }
 
-    fn end(self) -> Result<Value<'lua>> {
-        let lua = self.table.0.lua;
-        let table = lua.create_table()?;
-        table.raw_set(self.name, self.table)?;
+    fn end(self) -> Result<Value> {
+        let table = self.lua.create_table_with_capacity(0, 1)?;
+        table.raw_set(self.variant, self.table)?;
         Ok(Value::Table(table))
     }
 }

src/state/extra.rs

@@ -0,0 +1,246 @@
+use std::any::TypeId;
+use std::cell::UnsafeCell;
+use std::mem::MaybeUninit;
+use std::os::raw::{c_int, c_void};
+use std::ptr;
+use std::rc::Rc;
+use std::sync::Arc;
+
+use parking_lot::Mutex;
+use rustc_hash::FxHashMap;
+
+use crate::error::Result;
+use crate::state::RawLua;
+use crate::stdlib::StdLib;
+use crate::types::{AppData, ReentrantMutex, XRc};
+use crate::util::{get_internal_metatable, push_internal_userdata, TypeKey, WrappedFailure};
+
+#[cfg(any(feature = "luau", doc))]
+use crate::chunk::Compiler;
+
+#[cfg(feature = "async")]
+use {futures_util::task::noop_waker_ref, std::ptr::NonNull, std::task::Waker};
+
+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;
+
+/// Data associated with the Lua state.
+pub(crate) struct ExtraData {
+    pub(super) lua: MaybeUninit<Lua>,
+    pub(super) weak: MaybeUninit<WeakLua>,
+    pub(super) owned: bool,
+
+    pub(super) registered_userdata: 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)
+    pub(super) app_data: AppData,
+
+    pub(super) safe: bool,
+    pub(super) libs: StdLib,
+    // Used in module mode
+    pub(super) skip_memory_check: bool,
+
+    // Auxiliary thread to store references
+    pub(super) ref_thread: *mut ffi::lua_State,
+    pub(super) ref_stack_size: c_int,
+    pub(super) ref_stack_top: c_int,
+    pub(super) ref_free: Vec<c_int>,
+
+    // Pool of `WrappedFailure` enums in the ref thread (as userdata)
+    pub(super) wrapped_failure_pool: Vec<c_int>,
+    // Pool of `Thread`s (coroutines) for async execution
+    #[cfg(feature = "async")]
+    pub(super) thread_pool: Vec<c_int>,
+
+    // Address of `WrappedFailure` metatable
+    pub(super) wrapped_failure_mt_ptr: *const c_void,
+
+    // Waker for polling futures
+    #[cfg(feature = "async")]
+    pub(super) waker: NonNull<Waker>,
+
+    #[cfg(not(feature = "luau"))]
+    pub(super) hook_callback: Option<crate::types::HookCallback>,
+    #[cfg(not(feature = "luau"))]
+    pub(super) hook_thread: *mut ffi::lua_State,
+    #[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) sandboxed: bool,
+    #[cfg(feature = "luau")]
+    pub(super) compiler: Option<Compiler>,
+    #[cfg(feature = "luau-jit")]
+    pub(super) enable_jit: bool,
+}
+
+impl Drop for ExtraData {
+    fn drop(&mut self) {
+        unsafe {
+            if !self.owned {
+                self.lua.assume_init_drop();
+            }
+
+            self.weak.assume_init_drop();
+        }
+        *self.registry_unref_list.lock() = None;
+    }
+}
+
+static EXTRA_TYPE_KEY: u8 = 0;
+
+impl TypeKey for XRc<UnsafeCell<ExtraData>> {
+    #[inline(always)]
+    fn type_key() -> *const c_void {
+        &EXTRA_TYPE_KEY as *const u8 as *const c_void
+    }
+}
+
+impl ExtraData {
+    // Index of `error_traceback` function in auxiliary thread stack
+    #[cfg(any(feature = "lua51", feature = "luajit", feature = "luau"))]
+    pub(super) const ERROR_TRACEBACK_IDX: c_int = 1;
+
+    pub(super) unsafe fn init(state: *mut ffi::lua_State, owned: bool) -> XRc<UnsafeCell<Self>> {
+        // Create ref stack thread and place it in the registry to prevent it
+        // from being garbage collected.
+        let ref_thread = mlua_expect!(
+            protect_lua!(state, 0, 0, |state| {
+                let thread = ffi::lua_newthread(state);
+                ffi::luaL_ref(state, ffi::LUA_REGISTRYINDEX);
+                thread
+            }),
+            "Error while creating ref thread",
+        );
+
+        let wrapped_failure_mt_ptr = {
+            get_internal_metatable::<WrappedFailure>(state);
+            let ptr = ffi::lua_topointer(state, -1);
+            ffi::lua_pop(state, 1);
+            ptr
+        };
+
+        // Store `error_traceback` function on the ref stack
+        #[cfg(any(feature = "lua51", feature = "luajit", feature = "luau"))]
+        {
+            ffi::lua_pushcfunction(ref_thread, crate::util::error_traceback);
+            assert_eq!(ffi::lua_gettop(ref_thread), Self::ERROR_TRACEBACK_IDX);
+        }
+
+        #[allow(clippy::arc_with_non_send_sync)]
+        let extra = XRc::new(UnsafeCell::new(ExtraData {
+            lua: MaybeUninit::uninit(),
+            weak: MaybeUninit::uninit(),
+            owned,
+            registered_userdata: 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(),
+            safe: false,
+            libs: StdLib::NONE,
+            skip_memory_check: false,
+            ref_thread,
+            // We need some reserved stack space to move values in and out of the ref stack.
+            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),
+            #[cfg(feature = "async")]
+            thread_pool: Vec::new(),
+            wrapped_failure_mt_ptr,
+            #[cfg(feature = "async")]
+            waker: NonNull::from(noop_waker_ref()),
+            #[cfg(not(feature = "luau"))]
+            hook_callback: None,
+            #[cfg(not(feature = "luau"))]
+            hook_thread: ptr::null_mut(),
+            #[cfg(feature = "lua54")]
+            warn_callback: None,
+            #[cfg(feature = "luau")]
+            interrupt_callback: None,
+            #[cfg(feature = "luau")]
+            sandboxed: false,
+            #[cfg(feature = "luau")]
+            compiler: None,
+            #[cfg(feature = "luau-jit")]
+            enable_jit: true,
+        }));
+
+        // Store it in the registry
+        mlua_expect!(Self::store(&extra, state), "Error while storing extra data");
+
+        extra
+    }
+
+    pub(super) unsafe fn set_lua(&mut self, raw: &XRc<ReentrantMutex<RawLua>>) {
+        self.lua.write(Lua {
+            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 {
+        #[cfg(feature = "luau")]
+        if cfg!(not(feature = "module")) {
+            // In the main app we can use `lua_callbacks` to access ExtraData
+            return (*ffi::lua_callbacks(state)).userdata as *mut _;
+        }
+
+        let extra_key = &EXTRA_REGISTRY_KEY as *const u8 as *const c_void;
+        if ffi::lua_rawgetp(state, ffi::LUA_REGISTRYINDEX, extra_key) != ffi::LUA_TUSERDATA {
+            // `ExtraData` can be null only when Lua state is foreign.
+            // This case in used in `Lua::try_from_ptr()`.
+            ffi::lua_pop(state, 1);
+            return ptr::null_mut();
+        }
+        let extra_ptr = ffi::lua_touserdata(state, -1) as *mut Rc<UnsafeCell<ExtraData>>;
+        ffi::lua_pop(state, 1);
+        (*extra_ptr).get()
+    }
+
+    unsafe fn store(extra: &XRc<UnsafeCell<Self>>, state: *mut ffi::lua_State) -> Result<()> {
+        #[cfg(feature = "luau")]
+        if cfg!(not(feature = "module")) {
+            (*ffi::lua_callbacks(state)).userdata = extra.get() as *mut _;
+            return Ok(());
+        }
+
+        push_internal_userdata(state, XRc::clone(extra), true)?;
+        protect_lua!(state, 1, 0, fn(state) {
+            let extra_key = &EXTRA_REGISTRY_KEY as *const u8 as *const c_void;
+            ffi::lua_rawsetp(state, ffi::LUA_REGISTRYINDEX, extra_key);
+        })
+    }
+
+    #[inline(always)]
+    pub(super) unsafe fn lua(&self) -> &Lua {
+        self.lua.assume_init_ref()
+    }
+
+    #[inline(always)]
+    pub(super) unsafe fn raw_lua(&self) -> &RawLua {
+        &*self.lua.assume_init_ref().raw.data_ptr()
+    }
+
+    #[inline(always)]
+    pub(super) unsafe fn weak(&self) -> &WeakLua {
+        self.weak.assume_init_ref()
+    }
+}

src/state/util.rs

@@ -0,0 +1,180 @@
+use std::os::raw::c_int;
+use std::panic::{catch_unwind, AssertUnwindSafe};
+use std::ptr;
+use std::sync::Arc;
+
+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);
+
+impl<'a> StateGuard<'a> {
+    pub(super) 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> {
+    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>(
+    state: *mut ffi::lua_State,
+    mut extra: *mut ExtraData,
+    f: F,
+) -> R
+where
+    F: FnOnce(*mut ExtraData, c_int) -> Result<R>,
+{
+    if extra.is_null() {
+        extra = ExtraData::get(state);
+    }
+
+    let nargs = ffi::lua_gettop(state);
+
+    enum PreallocatedFailure {
+        New(*mut WrappedFailure),
+        Existing(i32),
+    }
+
+    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)
+                }
+            }
+        }
+
+        unsafe fn r#use(&self, state: *mut ffi::lua_State, extra: *mut ExtraData) -> *mut WrappedFailure {
+            let ref_thread = (*extra).ref_thread;
+            match *self {
+                PreallocatedFailure::New(ud) => {
+                    ffi::lua_settop(state, 1);
+                    ud
+                }
+                PreallocatedFailure::Existing(index) => {
+                    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_pushnil(ref_thread);
+                    ffi::lua_replace(ref_thread, index);
+                    (*extra).ref_free.push(index);
+                    ffi::lua_touserdata(state, -1) as *mut WrappedFailure
+                }
+            }
+        }
+
+        unsafe fn release(self, state: *mut ffi::lua_State, extra: *mut ExtraData) {
+            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);
+                    }
+                }
+            }
+        }
+    }
+
+    // We cannot shadow Rust errors with Lua ones, so we need to reserve pre-allocated memory
+    // 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))) {
+        Ok(Ok(r)) => {
+            // Return unused `WrappedFailure` to the pool
+            prealloc_failure.release(state, extra);
+            r
+        }
+        Ok(Err(err)) => {
+            let wrapped_error = prealloc_failure.r#use(state, extra);
+
+            // Build `CallbackError` with traceback
+            let traceback = if ffi::lua_checkstack(state, ffi::LUA_TRACEBACK_STACK) != 0 {
+                ffi::luaL_traceback(state, state, ptr::null(), 0);
+                let traceback = util::to_string(state, -1);
+                ffi::lua_pop(state, 1);
+                traceback
+            } else {
+                "<not enough stack space for traceback>".to_string()
+            };
+            let cause = Arc::new(err);
+            ptr::write(
+                wrapped_error,
+                WrappedFailure::Error(Error::CallbackError { traceback, cause }),
+            );
+            get_internal_metatable::<WrappedFailure>(state);
+            ffi::lua_setmetatable(state, -2);
+
+            ffi::lua_error(state)
+        }
+        Err(p) => {
+            let wrapped_panic = prealloc_failure.r#use(state, extra);
+            ptr::write(wrapped_panic, WrappedFailure::Panic(Some(p)));
+            get_internal_metatable::<WrappedFailure>(state);
+            ffi::lua_setmetatable(state, -2);
+            ffi::lua_error(state)
+        }
+    }
+}
+
+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

@@ -1,5 +1,4 @@
 use std::ops::{BitAnd, BitAndAssign, BitOr, BitOrAssign, BitXor, BitXorAssign};
-use std::u32;
 
 /// Flags describing the set of lua standard libraries to load.
 #[derive(Copy, Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]
@@ -9,12 +8,7 @@ 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(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

src/string.rs

@@ -1,8 +1,9 @@
-use std::borrow::{Borrow, Cow};
+use std::borrow::Borrow;
 use std::hash::{Hash, Hasher};
+use std::ops::Deref;
 use std::os::raw::c_void;
 use std::string::String as StdString;
-use std::{fmt, slice, str};
+use std::{cmp, fmt, slice, str};
 
 #[cfg(feature = "serialize")]
 use {
@@ -11,37 +12,17 @@ use {
 };
 
 use crate::error::{Error, Result};
-use crate::types::LuaRef;
+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.
 #[derive(Clone)]
-pub struct String<'lua>(pub(crate) LuaRef<'lua>);
+pub struct String(pub(crate) ValueRef);
 
-/// Owned handle to an internal Lua string.
-///
-/// The owned handle holds a *strong* reference to the current Lua instance.
-/// Be warned, if you place it into a Lua type (eg. [`UserData`] or a Rust callback), it is *very easy*
-/// to accidentally cause reference cycles that would prevent destroying Lua instance.
-///
-/// [`UserData`]: crate::UserData
-#[cfg(feature = "unstable")]
-#[cfg_attr(docsrs, doc(cfg(feature = "unstable")))]
-#[derive(Clone)]
-pub struct OwnedString(pub(crate) crate::types::LuaOwnedRef);
-
-#[cfg(feature = "unstable")]
-impl OwnedString {
-    /// Get borrowed handle to the underlying Lua string.
-    #[cfg_attr(feature = "send", allow(unused))]
-    pub const fn to_ref(&self) -> String {
-        String(self.0.to_ref())
-    }
-}
-
-impl<'lua> String<'lua> {
-    /// Get a `&str` slice if the Lua string is valid UTF-8.
+impl String {
+    /// Get a [`BorrowedStr`] if the Lua string is valid UTF-8.
     ///
     /// # Examples
     ///
@@ -60,15 +41,17 @@ impl<'lua> String<'lua> {
     /// # }
     /// ```
     #[inline]
-    pub fn to_str(&self) -> Result<&str> {
-        str::from_utf8(self.as_bytes()).map_err(|e| Error::FromLuaConversionError {
+    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))
     }
 
-    /// Converts this string to a [`Cow<str>`].
+    /// Converts this string to a [`StdString`].
     ///
     /// Any non-Unicode sequences are replaced with [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD].
     ///
@@ -87,8 +70,8 @@ impl<'lua> String<'lua> {
     /// # }
     /// ```
     #[inline]
-    pub fn to_string_lossy(&self) -> Cow<'_, str> {
-        StdString::from_utf8_lossy(self.as_bytes())
+    pub fn to_string_lossy(&self) -> StdString {
+        StdString::from_utf8_lossy(&self.as_bytes()).into_owned()
     }
 
     /// Get the bytes that make up this string.
@@ -109,14 +92,21 @@ impl<'lua> String<'lua> {
     /// # }
     /// ```
     #[inline]
-    pub fn as_bytes(&self) -> &[u8] {
-        let nulled = self.as_bytes_with_nul();
-        &nulled[..nulled.len() - 1]
+    pub fn as_bytes(&self) -> BorrowedBytes {
+        let (bytes, guard) = unsafe { self.to_slice() };
+        BorrowedBytes(&bytes[..bytes.len() - 1], guard)
     }
 
     /// Get the bytes that make up this string, including the trailing nul byte.
-    pub fn as_bytes_with_nul(&self) -> &[u8] {
-        let ref_thread = self.0.lua.ref_thread();
+    pub fn as_bytes_with_nul(&self) -> BorrowedBytes {
+        let (bytes, guard) = unsafe { self.to_slice() };
+        BorrowedBytes(bytes, guard)
+    }
+
+    unsafe fn to_slice(&self) -> (&[u8], Lua) {
+        let lua = self.0.lua.upgrade();
+        let rawlua = lua.lock();
+        let ref_thread = rawlua.ref_thread();
         unsafe {
             mlua_debug_assert!(
                 ffi::lua_type(ref_thread, self.0.index) == ffi::LUA_TSTRING,
@@ -128,11 +118,12 @@ impl<'lua> String<'lua> {
             // string type
             let data = ffi::lua_tolstring(ref_thread, self.0.index, &mut size);
 
-            slice::from_raw_parts(data as *const u8, size + 1)
+            drop(rawlua);
+            (slice::from_raw_parts(data as *const u8, size + 1), lua)
         }
     }
 
-    /// Converts the string to a generic C pointer.
+    /// Converts this string to a generic C pointer.
     ///
     /// There is no way to convert the pointer back to its original value.
     ///
@@ -141,21 +132,13 @@ impl<'lua> String<'lua> {
     pub fn to_pointer(&self) -> *const c_void {
         self.0.to_pointer()
     }
-
-    /// Convert this handle to owned version.
-    #[cfg(all(feature = "unstable", any(not(feature = "send"), doc)))]
-    #[cfg_attr(docsrs, doc(cfg(all(feature = "unstable", not(feature = "send")))))]
-    #[inline]
-    pub fn into_owned(self) -> OwnedString {
-        OwnedString(self.0.into_owned())
-    }
 }
 
-impl<'lua> fmt::Debug for String<'lua> {
+impl fmt::Debug for String {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let bytes = self.as_bytes();
         // Check if the string is valid utf8
-        if let Ok(s) = str::from_utf8(bytes) {
+        if let Ok(s) = str::from_utf8(&bytes) {
             return s.fmt(f);
         }
 
@@ -180,27 +163,14 @@ impl<'lua> fmt::Debug for String<'lua> {
     }
 }
 
-impl<'lua> AsRef<[u8]> for String<'lua> {
-    fn as_ref(&self) -> &[u8] {
-        self.as_bytes()
-    }
-}
-
-impl<'lua> Borrow<[u8]> for String<'lua> {
-    fn borrow(&self) -> &[u8] {
-        self.as_bytes()
-    }
-}
-
 // Lua strings are basically &[u8] slices, so implement PartialEq for anything resembling that.
 //
-// This makes our `String` comparable with `Vec<u8>`, `[u8]`, `&str`, `String` and `mlua::String`
-// itself.
+// This makes our `String` comparable with `Vec<u8>`, `[u8]`, `&str` and `String`.
 //
 // The only downside is that this disallows a comparison with `Cow<str>`, as that only implements
 // `AsRef<str>`, which collides with this impl. Requiring `AsRef<str>` would fix that, but limit us
 // in other ways.
-impl<'lua, T> PartialEq<T> for String<'lua>
+impl<T> PartialEq<T> for String
 where
     T: AsRef<[u8]> + ?Sized,
 {
@@ -209,55 +179,151 @@ where
     }
 }
 
-impl<'lua> Eq for String<'lua> {}
+impl PartialEq<String> for String {
+    fn eq(&self, other: &String) -> bool {
+        self.as_bytes() == other.as_bytes()
+    }
+}
 
-impl<'lua> Hash for String<'lua> {
+impl PartialEq<&String> for String {
+    fn eq(&self, other: &&String) -> bool {
+        self.as_bytes() == other.as_bytes()
+    }
+}
+
+impl Eq for String {}
+
+impl Hash for String {
     fn hash<H: Hasher>(&self, state: &mut H) {
         self.as_bytes().hash(state);
     }
 }
 
 #[cfg(feature = "serialize")]
-impl<'lua> Serialize for String<'lua> {
+impl Serialize for String {
     fn serialize<S>(&self, serializer: S) -> StdResult<S::Ok, S::Error>
     where
         S: Serializer,
     {
         match self.to_str() {
-            Ok(s) => serializer.serialize_str(s),
-            Err(_) => serializer.serialize_bytes(self.as_bytes()),
+            Ok(s) => serializer.serialize_str(&s),
+            Err(_) => serializer.serialize_bytes(&self.as_bytes()),
         }
     }
 }
 
-// Additional shortcuts
-#[cfg(feature = "unstable")]
-impl OwnedString {
-    /// Get a `&str` slice if the Lua string is valid UTF-8.
-    ///
-    /// This is a shortcut for [`String::to_str()`].
-    #[inline]
-    pub fn to_str(&self) -> Result<&str> {
-        let s = self.to_ref();
-        // Reattach lifetime to &self
-        unsafe { std::mem::transmute(s.to_str()) }
-    }
+/// A borrowed string (`&str`) that holds a strong reference to the Lua state.
+pub struct BorrowedStr<'a>(&'a str, #[allow(unused)] Lua);
 
-    /// Get the bytes that make up this string.
-    ///
-    /// This is a shortcut for [`String::as_bytes()`].
-    #[inline]
-    pub fn as_bytes(&self) -> &[u8] {
-        let s = self.to_ref();
-        // Reattach lifetime to &self
-        unsafe { std::mem::transmute(s.as_bytes()) }
+impl Deref for BorrowedStr<'_> {
+    type Target = str;
+
+    #[inline(always)]
+    fn deref(&self) -> &str {
+        self.0
     }
 }
 
-#[cfg(feature = "unstable")]
-impl fmt::Debug for OwnedString {
+impl Borrow<str> for BorrowedStr<'_> {
+    #[inline(always)]
+    fn borrow(&self) -> &str {
+        self.0
+    }
+}
+
+impl AsRef<str> for BorrowedStr<'_> {
+    #[inline(always)]
+    fn as_ref(&self) -> &str {
+        self.0
+    }
+}
+
+impl fmt::Display for BorrowedStr<'_> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        self.to_ref().fmt(f)
+        self.0.fmt(f)
+    }
+}
+
+impl fmt::Debug for BorrowedStr<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl<T> PartialEq<T> for BorrowedStr<'_>
+where
+    T: AsRef<str>,
+{
+    fn eq(&self, other: &T) -> bool {
+        self.0 == other.as_ref()
+    }
+}
+
+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())
+    }
+}
+
+/// A borrowed byte slice (`&[u8]`) that holds a strong reference to the Lua state.
+pub struct BorrowedBytes<'a>(&'a [u8], #[allow(unused)] Lua);
+
+impl Deref for BorrowedBytes<'_> {
+    type Target = [u8];
+
+    #[inline(always)]
+    fn deref(&self) -> &[u8] {
+        self.0
+    }
+}
+
+impl Borrow<[u8]> for BorrowedBytes<'_> {
+    #[inline(always)]
+    fn borrow(&self) -> &[u8] {
+        self.0
+    }
+}
+
+impl AsRef<[u8]> for BorrowedBytes<'_> {
+    #[inline(always)]
+    fn as_ref(&self) -> &[u8] {
+        self.0
+    }
+}
+
+impl fmt::Debug for BorrowedBytes<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl<T> PartialEq<T> for BorrowedBytes<'_>
+where
+    T: AsRef<[u8]>,
+{
+    fn eq(&self, other: &T) -> bool {
+        self.0 == other.as_ref()
+    }
+}
+
+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())
+    }
+}
+
+impl<'a> IntoIterator for BorrowedBytes<'a> {
+    type Item = &'a u8;
+    type IntoIter = slice::Iter<'a, u8>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.0.iter()
     }
 }
 
@@ -265,5 +331,12 @@ impl fmt::Debug for OwnedString {
 mod assertions {
     use super::*;
 
+    #[cfg(not(feature = "send"))]
     static_assertions::assert_not_impl_any!(String: Send);
+    #[cfg(feature = "send")]
+    static_assertions::assert_impl_all!(String: Send, Sync);
+    #[cfg(feature = "send")]
+    static_assertions::assert_impl_all!(BorrowedBytes: Send, Sync);
+    #[cfg(feature = "send")]
+    static_assertions::assert_impl_all!(BorrowedStr: Send, Sync);
 }

src/thread.rs

@@ -1,9 +1,10 @@
-use std::os::raw::c_int;
+use std::os::raw::{c_int, c_void};
 
 use crate::error::{Error, Result};
 #[allow(unused)]
-use crate::lua::Lua;
-use crate::types::LuaRef;
+use crate::state::Lua;
+use crate::state::RawLua;
+use crate::types::ValueRef;
 use crate::util::{check_stack, error_traceback_thread, pop_error, StackGuard};
 use crate::value::{FromLuaMulti, IntoLuaMulti};
 
@@ -15,7 +16,6 @@ use crate::{
 
 #[cfg(feature = "async")]
 use {
-    crate::{lua::ASYNC_POLL_PENDING, value::MultiValue},
     futures_util::stream::Stream,
     std::{
         future::Future,
@@ -29,45 +29,26 @@ use {
 /// Status of a Lua thread (coroutine).
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 pub enum ThreadStatus {
-    /// The thread was just created, or is suspended because it has called `coroutine.yield`.
+    /// The thread was just created or is suspended (yielded).
     ///
     /// If a thread is in this state, it can be resumed by calling [`Thread::resume`].
-    ///
-    /// [`Thread::resume`]: crate::Thread::resume
     Resumable,
-    /// Either the thread has finished executing, or the thread is currently running.
-    Unresumable,
+    /// The thread is currently running.
+    Running,
+    /// The thread has finished executing.
+    Finished,
     /// The thread has raised a Lua error during execution.
     Error,
 }
 
 /// Handle to an internal Lua thread (coroutine).
 #[derive(Clone, Debug)]
-pub struct Thread<'lua>(pub(crate) LuaRef<'lua>, pub(crate) *mut ffi::lua_State);
+pub struct Thread(pub(crate) ValueRef, pub(crate) *mut ffi::lua_State);
 
-/// Owned handle to an internal Lua thread (coroutine).
-///
-/// The owned handle holds a *strong* reference to the current Lua instance.
-/// Be warned, if you place it into a Lua type (eg. [`UserData`] or a Rust callback), it is *very easy*
-/// to accidentally cause reference cycles that would prevent destroying Lua instance.
-///
-/// [`UserData`]: crate::UserData
-#[cfg(feature = "unstable")]
-#[cfg_attr(docsrs, doc(cfg(feature = "unstable")))]
-#[derive(Clone, Debug)]
-pub struct OwnedThread(
-    pub(crate) crate::types::LuaOwnedRef,
-    pub(crate) *mut ffi::lua_State,
-);
-
-#[cfg(feature = "unstable")]
-impl OwnedThread {
-    /// Get borrowed handle to the underlying Lua table.
-    #[cfg_attr(feature = "send", allow(unused))]
-    pub const fn to_ref(&self) -> Thread {
-        Thread(self.0.to_ref(), self.1)
-    }
-}
+#[cfg(feature = "send")]
+unsafe impl Send for Thread {}
+#[cfg(feature = "send")]
+unsafe impl Sync for Thread {}
 
 /// Thread (coroutine) representation as an async [`Future`] or [`Stream`].
 ///
@@ -78,20 +59,15 @@ impl OwnedThread {
 #[cfg(feature = "async")]
 #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
 #[must_use = "futures do nothing unless you `.await` or poll them"]
-pub struct AsyncThread<'lua, R> {
-    thread: Thread<'lua>,
-    init_args: Option<Result<MultiValue<'lua>>>,
+pub struct AsyncThread<A, R> {
+    thread: Thread,
+    init_args: Option<A>,
     ret: PhantomData<R>,
     recycle: bool,
 }
 
-impl<'lua> Thread<'lua> {
+impl Thread {
     #[inline(always)]
-    pub(crate) fn new(r#ref: LuaRef<'lua>) -> Self {
-        let state = unsafe { ffi::lua_tothread(r#ref.lua.ref_thread(), r#ref.index) };
-        Thread(r#ref, state)
-    }
-
     const fn state(&self) -> *mut ffi::lua_State {
         self.1
     }
@@ -126,50 +102,48 @@ impl<'lua> Thread<'lua> {
     ///     end)
     /// "#).eval()?;
     ///
-    /// assert_eq!(thread.resume::<_, u32>(42)?, 123);
-    /// assert_eq!(thread.resume::<_, u32>(43)?, 987);
+    /// assert_eq!(thread.resume::<u32>(42)?, 123);
+    /// assert_eq!(thread.resume::<u32>(43)?, 987);
     ///
     /// // The coroutine has now returned, so `resume` will fail
-    /// match thread.resume::<_, u32>(()) {
-    ///     Err(Error::CoroutineInactive) => {},
+    /// match thread.resume::<u32>(()) {
+    ///     Err(Error::CoroutineUnresumable) => {},
     ///     unexpected => panic!("unexpected result {:?}", unexpected),
     /// }
     /// # Ok(())
     /// # }
     /// ```
-    pub fn resume<A, R>(&self, args: A) -> Result<R>
+    pub fn resume<R>(&self, args: impl IntoLuaMulti) -> Result<R>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua>,
+        R: FromLuaMulti,
     {
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
+        if self.status_inner(&lua) != ThreadStatus::Resumable {
+            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);
 
-            let nresults = self.resume_inner(args)?;
+            let nresults = self.resume_inner(&lua, args)?;
             check_stack(state, nresults + 1)?;
             ffi::lua_xmove(thread_state, state, nresults);
 
-            R::from_stack_multi(nresults, lua)
+            R::from_stack_multi(nresults, &lua)
         }
     }
 
     /// Resumes execution of this thread.
     ///
     /// It's similar to `resume()` but leaves `nresults` values on the thread stack.
-    unsafe fn resume_inner<A: IntoLuaMulti<'lua>>(&self, args: A) -> Result<c_int> {
-        let lua = self.0.lua;
+    unsafe fn resume_inner(&self, lua: &RawLua, args: impl IntoLuaMulti) -> Result<c_int> {
         let state = lua.state();
         let thread_state = self.state();
 
-        if self.status() != ThreadStatus::Resumable {
-            return Err(Error::CoroutineInactive);
-        }
-
-        let nargs = args.push_into_stack_multi(lua)?;
+        let nargs = args.push_into_stack_multi(&lua)?;
         if nargs > 0 {
             check_stack(thread_state, nargs)?;
             ffi::lua_xmove(state, thread_state, nargs);
@@ -183,10 +157,7 @@ impl<'lua> Thread<'lua> {
                 return Err(pop_error(thread_state, ret));
             }
             check_stack(state, 3)?;
-            protect_lua!(state, 0, 1, |state| error_traceback_thread(
-                state,
-                thread_state
-            ))?;
+            protect_lua!(state, 0, 1, |state| error_traceback_thread(state, thread_state))?;
             return Err(pop_error(state, ret));
         }
 
@@ -195,16 +166,23 @@ impl<'lua> Thread<'lua> {
 
     /// Gets the status of the thread.
     pub fn status(&self) -> ThreadStatus {
+        self.status_inner(&self.0.lua.lock())
+    }
+
+    /// Gets the status of the thread (internal implementation).
+    pub(crate) fn status_inner(&self, lua: &RawLua) -> ThreadStatus {
         let thread_state = self.state();
-        unsafe {
-            let status = ffi::lua_status(thread_state);
-            if status != ffi::LUA_OK && status != ffi::LUA_YIELD {
-                ThreadStatus::Error
-            } else if status == ffi::LUA_YIELD || ffi::lua_gettop(thread_state) > 0 {
-                ThreadStatus::Resumable
-            } else {
-                ThreadStatus::Unresumable
-            }
+        if thread_state == lua.state() {
+            // The thread is currently running
+            return ThreadStatus::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
         }
     }
 
@@ -218,7 +196,7 @@ impl<'lua> Thread<'lua> {
     where
         F: Fn(&Lua, Debug) -> Result<()> + MaybeSend + 'static,
     {
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         unsafe {
             lua.set_thread_hook(self.state(), triggers, callback);
         }
@@ -240,8 +218,12 @@ impl<'lua> Thread<'lua> {
     /// [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<'lua>) -> Result<()> {
-        let lua = self.0.lua;
+    pub fn reset(&self, func: crate::function::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")))]
@@ -289,7 +271,7 @@ impl<'lua> Thread<'lua> {
     ///
     /// ```
     /// # use mlua::{Lua, Result, Thread};
-    /// use futures::stream::TryStreamExt;
+    /// use futures_util::stream::TryStreamExt;
     /// # #[tokio::main]
     /// # async fn main() -> Result<()> {
     /// # let lua = Lua::new();
@@ -303,7 +285,7 @@ impl<'lua> Thread<'lua> {
     ///     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;
@@ -316,12 +298,10 @@ impl<'lua> Thread<'lua> {
     /// ```
     #[cfg(feature = "async")]
     #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
-    pub fn into_async<A, R>(self, args: A) -> AsyncThread<'lua, R>
+    pub fn into_async<R>(self, args: impl IntoLuaMulti) -> AsyncThread<impl IntoLuaMulti, R>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua>,
+        R: FromLuaMulti,
     {
-        let args = args.into_lua_multi(self.0.lua);
         AsyncThread {
             thread: self,
             init_args: Some(args),
@@ -348,14 +328,14 @@ impl<'lua> Thread<'lua> {
     /// let lua = Lua::new();
     /// let thread = lua.create_thread(lua.create_function(|lua2, ()| {
     ///     lua2.load("var = 123").exec()?;
-    ///     assert_eq!(lua2.globals().get::<_, u32>("var")?, 123);
+    ///     assert_eq!(lua2.globals().get::<u32>("var")?, 123);
     ///     Ok(())
     /// })?)?;
     /// thread.sandbox()?;
     /// thread.resume(())?;
     ///
     /// // The global environment should be unchanged
-    /// assert_eq!(lua.globals().get::<_, Option<u32>>("var")?, None);
+    /// assert_eq!(lua.globals().get::<Option<u32>>("var")?, None);
     /// # Ok(())
     /// # }
     /// ```
@@ -365,7 +345,7 @@ impl<'lua> Thread<'lua> {
     #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
     #[doc(hidden)]
     pub fn sandbox(&self) -> Result<()> {
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         let thread_state = self.state();
         unsafe {
@@ -375,43 +355,25 @@ impl<'lua> Thread<'lua> {
         }
     }
 
-    /// Convert this handle to owned version.
-    #[cfg(all(feature = "unstable", any(not(feature = "send"), doc)))]
-    #[cfg_attr(docsrs, doc(cfg(all(feature = "unstable", not(feature = "send")))))]
+    /// Converts this thread to a generic C pointer.
+    ///
+    /// There is no way to convert the pointer back to its original value.
+    ///
+    /// Typically this function is used only for hashing and debug information.
     #[inline]
-    pub fn into_owned(self) -> OwnedThread {
-        OwnedThread(self.0.into_owned(), self.1)
+    pub fn to_pointer(&self) -> *const c_void {
+        self.0.to_pointer()
     }
 }
 
-impl<'lua> PartialEq for Thread<'lua> {
+impl PartialEq for Thread {
     fn eq(&self, other: &Self) -> bool {
         self.0 == other.0
     }
 }
 
-// Additional shortcuts
-#[cfg(feature = "unstable")]
-impl OwnedThread {
-    /// Resumes execution of this thread.
-    ///
-    /// See [`Thread::resume()`] for more details.
-    pub fn resume<'lua, A, R>(&'lua self, args: A) -> Result<R>
-    where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua>,
-    {
-        self.to_ref().resume(args)
-    }
-
-    /// Gets the status of the thread.
-    pub fn status(&self) -> ThreadStatus {
-        self.to_ref().status()
-    }
-}
-
 #[cfg(feature = "async")]
-impl<'lua, R> AsyncThread<'lua, R> {
+impl<A, R> AsyncThread<A, R> {
     #[inline]
     pub(crate) fn set_recyclable(&mut self, recyclable: bool) {
         self.recycle = recyclable;
@@ -420,19 +382,20 @@ impl<'lua, R> AsyncThread<'lua, R> {
 
 #[cfg(feature = "async")]
 #[cfg(any(feature = "lua54", feature = "luau"))]
-impl<'lua, R> Drop for AsyncThread<'lua, R> {
+impl<A, R> Drop for AsyncThread<A, R> {
     fn drop(&mut self) {
         if self.recycle {
-            unsafe {
-                let lua = self.thread.0.lua;
-                // 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() == ThreadStatus::Error {
-                        #[cfg(not(feature = "vendored"))]
-                        ffi::lua_resetthread(self.thread.state());
-                        #[cfg(feature = "vendored")]
-                        ffi::lua_closethread(self.thread.state(), lua.state());
+            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());
+                        }
                     }
                 }
             }
@@ -441,31 +404,28 @@ impl<'lua, R> Drop for AsyncThread<'lua, R> {
 }
 
 #[cfg(feature = "async")]
-impl<'lua, R> Stream for AsyncThread<'lua, R>
-where
-    R: FromLuaMulti<'lua>,
-{
+impl<A: IntoLuaMulti, R: FromLuaMulti> Stream for AsyncThread<A, R> {
     type Item = Result<R>;
 
     fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
-        if self.thread.status() != ThreadStatus::Resumable {
+        let lua = self.thread.0.lua.lock();
+        if self.thread.status_inner(&lua) != ThreadStatus::Resumable {
             return Poll::Ready(None);
         }
 
-        let lua = self.thread.0.lua;
         let state = lua.state();
         let thread_state = self.thread.state();
         unsafe {
             let _sg = StackGuard::new(state);
             let _thread_sg = StackGuard::with_top(thread_state, 0);
-            let _wg = WakerGuard::new(lua, cx.waker());
+            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(args?)?
+                this.thread.resume_inner(&lua, args)?
             } else {
-                this.thread.resume_inner(())?
+                this.thread.resume_inner(&lua, ())?
             };
 
             if nresults == 1 && is_poll_pending(thread_state) {
@@ -476,37 +436,34 @@ where
             ffi::lua_xmove(thread_state, state, nresults);
 
             cx.waker().wake_by_ref();
-            Poll::Ready(Some(R::from_stack_multi(nresults, lua)))
+            Poll::Ready(Some(R::from_stack_multi(nresults, &lua)))
         }
     }
 }
 
 #[cfg(feature = "async")]
-impl<'lua, R> Future for AsyncThread<'lua, R>
-where
-    R: FromLuaMulti<'lua>,
-{
+impl<A: IntoLuaMulti, R: FromLuaMulti> Future for AsyncThread<A, R> {
     type Output = Result<R>;
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-        if self.thread.status() != ThreadStatus::Resumable {
-            return Poll::Ready(Err(Error::CoroutineInactive));
+        let lua = self.thread.0.lua.lock();
+        if self.thread.status_inner(&lua) != ThreadStatus::Resumable {
+            return Poll::Ready(Err(Error::CoroutineUnresumable));
         }
 
-        let lua = self.thread.0.lua;
         let state = lua.state();
         let thread_state = self.thread.state();
         unsafe {
             let _sg = StackGuard::new(state);
             let _thread_sg = StackGuard::with_top(thread_state, 0);
-            let _wg = WakerGuard::new(lua, cx.waker());
+            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(args?)?
+                this.thread.resume_inner(&lua, args)?
             } else {
-                this.thread.resume_inner(())?
+                this.thread.resume_inner(&lua, ())?
             };
 
             if nresults == 1 && is_poll_pending(thread_state) {
@@ -522,7 +479,7 @@ where
             check_stack(state, nresults + 1)?;
             ffi::lua_xmove(thread_state, state, nresults);
 
-            Poll::Ready(R::from_stack_multi(nresults, lua))
+            Poll::Ready(R::from_stack_multi(nresults, &lua))
         }
     }
 }
@@ -530,17 +487,12 @@ where
 #[cfg(feature = "async")]
 #[inline(always)]
 unsafe fn is_poll_pending(state: *mut ffi::lua_State) -> bool {
-    if ffi::lua_islightuserdata(state, -1) != 0 {
-        let stack_ptr = ffi::lua_touserdata(state, -1) as *const u8;
-        let pending_ptr = &ASYNC_POLL_PENDING as *const u8;
-        return std::ptr::eq(stack_ptr, pending_ptr);
-    }
-    false
+    ffi::lua_tolightuserdata(state, -1) == Lua::poll_pending().0
 }
 
 #[cfg(feature = "async")]
 struct WakerGuard<'lua, 'a> {
-    lua: &'lua Lua,
+    lua: &'lua RawLua,
     prev: NonNull<Waker>,
     _phantom: PhantomData<&'a ()>,
 }
@@ -548,7 +500,7 @@ struct WakerGuard<'lua, 'a> {
 #[cfg(feature = "async")]
 impl<'lua, 'a> WakerGuard<'lua, 'a> {
     #[inline]
-    pub fn new(lua: &'lua Lua, waker: &'a Waker) -> Result<WakerGuard<'lua, 'a>> {
+    pub fn new(lua: &'lua RawLua, waker: &'a Waker) -> Result<WakerGuard<'lua, 'a>> {
         let prev = unsafe { lua.set_waker(NonNull::from(waker)) };
         Ok(WakerGuard {
             lua,
@@ -569,5 +521,12 @@ impl<'lua, 'a> Drop for WakerGuard<'lua, 'a> {
 mod assertions {
     use super::*;
 
+    #[cfg(not(feature = "send"))]
     static_assertions::assert_not_impl_any!(Thread: Send);
+    #[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);
+    #[cfg(all(feature = "async", feature = "send"))]
+    static_assertions::assert_impl_all!(AsyncThread<(), ()>: Send, Sync);
 }

src/traits.rs

@@ -0,0 +1,78 @@
+use std::string::String as StdString;
+
+use crate::error::Result;
+use crate::private::Sealed;
+use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti};
+
+#[cfg(feature = "async")]
+use std::future::Future;
+
+/// A trait for types that can be used as Lua objects (usually table and userdata).
+pub trait ObjectLike: Sealed {
+    /// Gets the value associated to `key` from the object, assuming it has `__index` metamethod.
+    fn get<V: FromLua>(&self, key: impl IntoLua) -> Result<V>;
+
+    /// Sets the value associated to `key` in the object, assuming it has `__newindex` metamethod.
+    fn set(&self, key: impl IntoLua, value: impl IntoLua) -> Result<()>;
+
+    /// Calls the object as a function assuming it has `__call` metamethod.
+    ///
+    /// The metamethod is called with the object as its first argument, followed by the passed
+    /// arguments.
+    fn call<R>(&self, args: impl IntoLuaMulti) -> Result<R>
+    where
+        R: FromLuaMulti;
+
+    /// Asynchronously calls the object as a function assuming it has `__call` metamethod.
+    ///
+    /// The metamethod is called with the object as its first argument, followed by the passed
+    /// arguments.
+    #[cfg(feature = "async")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
+    fn call_async<R>(&self, args: impl IntoLuaMulti) -> impl Future<Output = Result<R>>
+    where
+        R: FromLuaMulti;
+
+    /// Gets the function associated to key `name` from the object and calls it,
+    /// passing the object itself along with `args` as function arguments.
+    fn call_method<R>(&self, name: &str, args: impl IntoLuaMulti) -> Result<R>
+    where
+        R: FromLuaMulti;
+
+    /// 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>>
+    where
+        R: FromLuaMulti;
+
+    /// Gets the function associated to key `name` from the object and calls it,
+    /// passing `args` as function arguments.
+    ///
+    /// This might invoke the `__index` metamethod.
+    fn call_function<R>(&self, name: &str, args: impl IntoLuaMulti) -> Result<R>
+    where
+        R: FromLuaMulti;
+
+    /// 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>>
+    where
+        R: FromLuaMulti;
+
+    /// Converts the object to a string in a human-readable format.
+    ///
+    /// This might invoke the `__tostring` metamethod.
+    fn to_string(&self) -> Result<StdString>;
+}

src/types.rs

@@ -1,28 +1,26 @@
-use std::any::{Any, TypeId};
-use std::cell::{Cell, Ref, RefCell, RefMut, UnsafeCell};
-use std::hash::{Hash, Hasher};
-use std::ops::{Deref, DerefMut};
+use std::cell::UnsafeCell;
+use std::fmt;
 use std::os::raw::{c_int, c_void};
-use std::result::Result as StdResult;
-use std::sync::atomic::{AtomicBool, Ordering};
-use std::sync::{Arc, Mutex};
-use std::{fmt, mem, ptr};
-
-use rustc_hash::FxHashMap;
+use std::rc::Rc;
 
 use crate::error::Result;
 #[cfg(not(feature = "luau"))]
 use crate::hook::Debug;
-use crate::lua::{ExtraData, Lua};
+use crate::state::{ExtraData, Lua, RawLua, WeakLua};
 
-#[cfg(feature = "async")]
-use {crate::value::MultiValue, futures_util::future::LocalBoxFuture};
+// Re-export mutex wrappers
+pub(crate) use sync::{ArcReentrantMutexGuard, ReentrantMutex, ReentrantMutexGuard, XRc, XWeak};
 
-#[cfg(feature = "unstable")]
-use {crate::lua::LuaInner, std::marker::PhantomData};
+#[cfg(all(feature = "async", feature = "send"))]
+pub(crate) type BoxFuture<'a, T> = futures_util::future::BoxFuture<'a, T>;
 
-#[cfg(all(feature = "luau", feature = "serialize"))]
-use serde::ser::{Serialize, SerializeTupleStruct, Serializer};
+#[cfg(all(feature = "async", not(feature = "send")))]
+pub(crate) type BoxFuture<'a, T> = futures_util::future::LocalBoxFuture<'a, T>;
+
+pub use app_data::{AppData, AppDataRef, AppDataRefMut};
+pub use registry_key::RegistryKey;
+#[cfg(any(feature = "luau", doc))]
+pub use vector::Vector;
 
 /// Type of Lua integer numbers.
 pub type Integer = ffi::lua_Integer;
@@ -43,24 +41,37 @@ pub(crate) enum SubtypeId {
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 pub struct LightUserData(pub *mut c_void);
 
-pub(crate) type Callback<'lua, 'a> = Box<dyn Fn(&'lua Lua, c_int) -> Result<c_int> + 'a>;
+#[cfg(feature = "send")]
+unsafe impl Send for LightUserData {}
+#[cfg(feature = "send")]
+unsafe impl Sync for LightUserData {}
+
+#[cfg(feature = "send")]
+pub(crate) type Callback = Box<dyn Fn(&RawLua, c_int) -> Result<c_int> + Send + 'static>;
+
+#[cfg(not(feature = "send"))]
+pub(crate) type Callback = Box<dyn Fn(&RawLua, c_int) -> Result<c_int> + 'static>;
 
 pub(crate) struct Upvalue<T> {
     pub(crate) data: T,
-    pub(crate) extra: Arc<UnsafeCell<ExtraData>>,
+    pub(crate) extra: XRc<UnsafeCell<ExtraData>>,
 }
 
-pub(crate) type CallbackUpvalue = Upvalue<Callback<'static, 'static>>;
+pub(crate) type CallbackUpvalue = Upvalue<Callback>;
+
+#[cfg(all(feature = "async", feature = "send"))]
+pub(crate) type AsyncCallback =
+    Box<dyn for<'a> Fn(&'a RawLua, c_int) -> BoxFuture<'a, Result<c_int>> + Send + 'static>;
+
+#[cfg(all(feature = "async", not(feature = "send")))]
+pub(crate) type AsyncCallback =
+    Box<dyn for<'a> Fn(&'a RawLua, c_int) -> BoxFuture<'a, Result<c_int>> + 'static>;
 
 #[cfg(feature = "async")]
-pub(crate) type AsyncCallback<'lua, 'a> =
-    Box<dyn Fn(&'lua Lua, MultiValue<'lua>) -> LocalBoxFuture<'lua, Result<c_int>> + 'a>;
+pub(crate) type AsyncCallbackUpvalue = Upvalue<AsyncCallback>;
 
 #[cfg(feature = "async")]
-pub(crate) type AsyncCallbackUpvalue = Upvalue<AsyncCallback<'static, 'static>>;
-
-#[cfg(feature = "async")]
-pub(crate) type AsyncPollUpvalue = Upvalue<LocalBoxFuture<'static, Result<c_int>>>;
+pub(crate) type AsyncPollUpvalue = Upvalue<BoxFuture<'static, Result<c_int>>>;
 
 /// Type to set next Luau VM action after executing interrupt function.
 #[cfg(any(feature = "luau", doc))]
@@ -71,16 +82,16 @@ pub enum VmState {
 }
 
 #[cfg(all(feature = "send", not(feature = "luau")))]
-pub(crate) type HookCallback = Arc<dyn Fn(&Lua, Debug) -> Result<()> + Send>;
+pub(crate) type HookCallback = Rc<dyn Fn(&Lua, Debug) -> Result<()> + Send>;
 
 #[cfg(all(not(feature = "send"), not(feature = "luau")))]
-pub(crate) type HookCallback = Arc<dyn Fn(&Lua, Debug) -> Result<()>>;
+pub(crate) type HookCallback = Rc<dyn Fn(&Lua, Debug) -> Result<()>>;
 
-#[cfg(all(feature = "luau", feature = "send"))]
-pub(crate) type InterruptCallback = Arc<dyn Fn(&Lua) -> Result<VmState> + Send>;
+#[cfg(all(feature = "send", feature = "luau"))]
+pub(crate) type InterruptCallback = Rc<dyn Fn(&Lua) -> Result<VmState> + Send>;
 
-#[cfg(all(feature = "luau", not(feature = "send")))]
-pub(crate) type InterruptCallback = Arc<dyn Fn(&Lua) -> Result<VmState>>;
+#[cfg(all(not(feature = "send"), feature = "luau"))]
+pub(crate) type InterruptCallback = Rc<dyn Fn(&Lua) -> Result<VmState>>;
 
 #[cfg(all(feature = "send", feature = "lua54"))]
 pub(crate) type WarnCallback = Box<dyn Fn(&Lua, &str, bool) -> Result<()> + Send>;
@@ -88,6 +99,7 @@ pub(crate) type WarnCallback = Box<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<()>>;
 
+/// A trait that adds `Send` requirement if `send` feature is enabled.
 #[cfg(feature = "send")]
 pub trait MaybeSend: Send {}
 #[cfg(feature = "send")]
@@ -98,195 +110,19 @@ pub trait MaybeSend {}
 #[cfg(not(feature = "send"))]
 impl<T> MaybeSend for T {}
 
-/// A Luau vector type.
-///
-/// By default vectors are 3-dimensional, but can be 4-dimensional
-/// if the `luau-vector4` feature is enabled.
-#[cfg(any(feature = "luau", doc))]
-#[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
-#[derive(Debug, Default, Clone, Copy, PartialEq)]
-pub struct Vector(pub(crate) [f32; Self::SIZE]);
-
-#[cfg(any(feature = "luau", doc))]
-impl fmt::Display for Vector {
-    #[rustfmt::skip]
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        #[cfg(not(feature = "luau-vector4"))]
-        return write!(f, "vector({}, {}, {})", self.x(), self.y(), self.z());
-        #[cfg(feature = "luau-vector4")]
-        return write!(f, "vector({}, {}, {}, {})", self.x(), self.y(), self.z(), self.w());
-    }
-}
-
-#[cfg(any(feature = "luau", doc))]
-impl Vector {
-    pub(crate) const SIZE: usize = if cfg!(feature = "luau-vector4") { 4 } else { 3 };
-
-    /// Creates a new vector.
-    #[cfg(not(feature = "luau-vector4"))]
-    pub const fn new(x: f32, y: f32, z: f32) -> Self {
-        Self([x, y, z])
-    }
-
-    /// Creates a new vector.
-    #[cfg(feature = "luau-vector4")]
-    pub const fn new(x: f32, y: f32, z: f32, w: f32) -> Self {
-        Self([x, y, z, w])
-    }
-
-    /// Creates a new vector with all components set to `0.0`.
-    #[doc(hidden)]
-    pub const fn zero() -> Self {
-        Self([0.0; Self::SIZE])
-    }
-
-    /// Returns 1st component of the vector.
-    pub const fn x(&self) -> f32 {
-        self.0[0]
-    }
-
-    /// Returns 2nd component of the vector.
-    pub const fn y(&self) -> f32 {
-        self.0[1]
-    }
-
-    /// Returns 3rd component of the vector.
-    pub const fn z(&self) -> f32 {
-        self.0[2]
-    }
-
-    /// Returns 4th component of the vector.
-    #[cfg(any(feature = "luau-vector4", doc))]
-    #[cfg_attr(docsrs, doc(cfg(feature = "luau-vector4")))]
-    pub const fn w(&self) -> f32 {
-        self.0[3]
-    }
-}
-
-#[cfg(all(feature = "luau", feature = "serialize"))]
-impl Serialize for Vector {
-    fn serialize<S: Serializer>(&self, serializer: S) -> StdResult<S::Ok, S::Error> {
-        let mut ts = serializer.serialize_tuple_struct("Vector", Self::SIZE)?;
-        ts.serialize_field(&self.x())?;
-        ts.serialize_field(&self.y())?;
-        ts.serialize_field(&self.z())?;
-        #[cfg(feature = "luau-vector4")]
-        ts.serialize_field(&self.w())?;
-        ts.end()
-    }
-}
-
-#[cfg(any(feature = "luau", doc))]
-impl PartialEq<[f32; Self::SIZE]> for Vector {
-    #[inline]
-    fn eq(&self, other: &[f32; Self::SIZE]) -> bool {
-        self.0 == *other
-    }
-}
-
 pub(crate) struct DestructedUserdata;
 
-/// An auto generated key into the Lua registry.
-///
-/// This is a handle to a value stored inside the Lua registry. It is not automatically
-/// garbage collected on Drop, but it can be removed with [`Lua::remove_registry_value`],
-/// 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`].
-///
-/// [`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: c_int,
-    pub(crate) is_nil: AtomicBool,
-    pub(crate) unref_list: Arc<Mutex<Option<Vec<c_int>>>>,
-}
-
-impl fmt::Debug for RegistryKey {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "RegistryKey({})", self.registry_id)
-    }
-}
-
-impl Hash for RegistryKey {
-    fn hash<H: Hasher>(&self, state: &mut H) {
-        self.registry_id.hash(state)
-    }
-}
-
-impl PartialEq for RegistryKey {
-    fn eq(&self, other: &RegistryKey) -> bool {
-        self.registry_id == other.registry_id && Arc::ptr_eq(&self.unref_list, &other.unref_list)
-    }
-}
-
-impl Eq for RegistryKey {}
-
-impl Drop for RegistryKey {
-    fn drop(&mut self) {
-        // We don't need to collect nil slot
-        if self.registry_id > ffi::LUA_REFNIL {
-            let mut unref_list = mlua_expect!(self.unref_list.lock(), "unref list poisoned");
-            if let Some(list) = unref_list.as_mut() {
-                list.push(self.registry_id);
-            }
-        }
-    }
-}
-
-impl RegistryKey {
-    // Creates a new instance of `RegistryKey`
-    pub(crate) const fn new(id: c_int, unref_list: Arc<Mutex<Option<Vec<c_int>>>>) -> Self {
-        RegistryKey {
-            registry_id: id,
-            is_nil: AtomicBool::new(id == ffi::LUA_REFNIL),
-            unref_list,
-        }
-    }
-
-    // Destroys the `RegistryKey` without adding to the unref list
-    pub(crate) fn take(self) -> c_int {
-        let registry_id = self.registry_id;
-        unsafe {
-            ptr::read(&self.unref_list);
-            mem::forget(self);
-        }
-        registry_id
-    }
-
-    // Returns true if this `RegistryKey` holds a nil value
-    #[inline(always)]
-    pub(crate) fn is_nil(&self) -> bool {
-        self.is_nil.load(Ordering::Relaxed)
-    }
-
-    // Marks value of this `RegistryKey` as `Nil`
-    #[inline(always)]
-    pub(crate) fn set_nil(&self, enabled: bool) {
-        // We cannot replace previous value with nil in as this will break
-        // Lua mechanism to find free keys.
-        // Instead, we set a special flag to mark value as nil.
-        self.is_nil.store(enabled, Ordering::Relaxed);
-    }
-}
-
-pub(crate) struct LuaRef<'lua> {
-    pub(crate) lua: &'lua Lua,
+pub(crate) struct ValueRef {
+    pub(crate) lua: WeakLua,
     pub(crate) index: c_int,
     pub(crate) drop: bool,
 }
 
-impl<'lua> LuaRef<'lua> {
-    pub(crate) const fn new(lua: &'lua Lua, index: c_int) -> Self {
-        LuaRef {
-            lua,
+impl ValueRef {
+    #[inline]
+    pub(crate) fn new(lua: &RawLua, index: c_int) -> Self {
+        ValueRef {
+            lua: lua.weak().clone(),
             index,
             drop: true,
         }
@@ -294,249 +130,67 @@ impl<'lua> LuaRef<'lua> {
 
     #[inline]
     pub(crate) fn to_pointer(&self) -> *const c_void {
-        unsafe { ffi::lua_topointer(self.lua.ref_thread(), self.index) }
+        let lua = self.lua.lock();
+        unsafe { ffi::lua_topointer(lua.ref_thread(), self.index) }
     }
 
-    #[cfg(feature = "unstable")]
+    /// Returns a copy of the value, which is valid as long as the original value is held.
     #[inline]
-    pub(crate) fn into_owned(self) -> LuaOwnedRef {
-        assert!(self.drop, "Cannot turn non-drop reference into owned");
-        let owned_ref = LuaOwnedRef::new(self.lua.clone(), self.index);
-        mem::forget(self);
-        owned_ref
-    }
-}
-
-impl<'lua> fmt::Debug for LuaRef<'lua> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "Ref({:p})", self.to_pointer())
-    }
-}
-
-impl<'lua> Clone for LuaRef<'lua> {
-    fn clone(&self) -> Self {
-        self.lua.clone_ref(self)
-    }
-}
-
-impl<'lua> Drop for LuaRef<'lua> {
-    fn drop(&mut self) {
-        if self.drop {
-            self.lua.drop_ref_index(self.index);
-        }
-    }
-}
-
-impl<'lua> PartialEq for LuaRef<'lua> {
-    fn eq(&self, other: &Self) -> bool {
-        let ref_thread = self.lua.ref_thread();
-        assert!(
-            ref_thread == other.lua.ref_thread(),
-            "Lua instance passed Value created from a different main Lua state"
-        );
-        unsafe { ffi::lua_rawequal(ref_thread, self.index, other.index) == 1 }
-    }
-}
-
-#[cfg(feature = "unstable")]
-pub(crate) struct LuaOwnedRef {
-    pub(crate) inner: Arc<LuaInner>,
-    pub(crate) index: c_int,
-    _non_send: PhantomData<*const ()>,
-}
-
-#[cfg(feature = "unstable")]
-impl fmt::Debug for LuaOwnedRef {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "OwnedRef({:p})", self.to_ref().to_pointer())
-    }
-}
-
-#[cfg(feature = "unstable")]
-impl Clone for LuaOwnedRef {
-    fn clone(&self) -> Self {
-        self.to_ref().clone().into_owned()
-    }
-}
-
-#[cfg(feature = "unstable")]
-impl Drop for LuaOwnedRef {
-    fn drop(&mut self) {
-        let lua: &Lua = unsafe { mem::transmute(&self.inner) };
-        lua.drop_ref_index(self.index);
-    }
-}
-
-#[cfg(feature = "unstable")]
-impl LuaOwnedRef {
-    pub(crate) const fn new(inner: Arc<LuaInner>, index: c_int) -> Self {
-        LuaOwnedRef {
-            inner,
-            index,
-            _non_send: PhantomData,
-        }
-    }
-
-    pub(crate) const fn to_ref(&self) -> LuaRef {
-        LuaRef {
-            lua: unsafe { mem::transmute(&self.inner) },
+    pub(crate) fn copy(&self) -> Self {
+        ValueRef {
+            lua: self.lua.clone(),
             index: self.index,
             drop: false,
         }
     }
 }
 
-#[derive(Debug, Default)]
-pub(crate) struct AppData {
-    #[cfg(not(feature = "send"))]
-    container: UnsafeCell<FxHashMap<TypeId, RefCell<Box<dyn Any>>>>,
-    #[cfg(feature = "send")]
-    container: UnsafeCell<FxHashMap<TypeId, RefCell<Box<dyn Any + Send>>>>,
-    borrow: Cell<usize>,
-}
-
-impl AppData {
-    #[track_caller]
-    pub(crate) fn insert<T: MaybeSend + 'static>(&self, data: T) -> Option<T> {
-        match self.try_insert(data) {
-            Ok(data) => data,
-            Err(_) => panic!("cannot mutably borrow app data container"),
-        }
-    }
-
-    pub(crate) fn try_insert<T: MaybeSend + 'static>(&self, data: T) -> StdResult<Option<T>, T> {
-        if self.borrow.get() != 0 {
-            return Err(data);
-        }
-        // SAFETY: we checked that there are no other references to the container
-        Ok(unsafe { &mut *self.container.get() }
-            .insert(TypeId::of::<T>(), RefCell::new(Box::new(data)))
-            .and_then(|data| data.into_inner().downcast::<T>().ok().map(|data| *data)))
-    }
-
-    #[track_caller]
-    pub(crate) fn borrow<T: 'static>(&self) -> 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,
-        })
-    }
-
-    #[track_caller]
-    pub(crate) fn borrow_mut<T: 'static>(&self) -> Option<AppDataRefMut<T>> {
-        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,
-        })
-    }
-
-    #[track_caller]
-    pub(crate) fn remove<T: 'static>(&self) -> Option<T> {
-        if self.borrow.get() != 0 {
-            panic!("cannot mutably borrow app data container");
-        }
-        // SAFETY: we checked that there are no other references to the container
-        unsafe { &mut *self.container.get() }
-            .remove(&TypeId::of::<T>())?
-            .into_inner()
-            .downcast::<T>()
-            .ok()
-            .map(|data| *data)
+impl fmt::Debug for ValueRef {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "Ref({:p})", self.to_pointer())
     }
 }
 
-/// A wrapper type for an immutably borrowed value from an app data container.
-///
-/// This type is similar to [`Ref`].
-pub struct AppDataRef<'a, T: ?Sized + 'a> {
-    data: Ref<'a, T>,
-    borrow: &'a Cell<usize>,
+impl Clone for ValueRef {
+    fn clone(&self) -> Self {
+        unsafe { self.lua.lock().clone_ref(self) }
+    }
 }
 
-impl<T: ?Sized> Drop for AppDataRef<'_, T> {
+impl Drop for ValueRef {
     fn drop(&mut self) {
-        self.borrow.set(self.borrow.get() - 1);
+        if self.drop {
+            if let Some(lua) = self.lua.try_lock() {
+                unsafe { lua.drop_ref(self) };
+            }
+        }
     }
 }
 
-impl<T: ?Sized> Deref for AppDataRef<'_, T> {
-    type Target = T;
-
-    #[inline]
-    fn deref(&self) -> &Self::Target {
-        &self.data
+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<T: ?Sized + fmt::Display> fmt::Display for AppDataRef<'_, T> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        (**self).fmt(f)
-    }
-}
+mod app_data;
+mod registry_key;
+mod sync;
 
-impl<T: ?Sized + fmt::Debug> fmt::Debug for AppDataRef<'_, T> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        (**self).fmt(f)
-    }
-}
-
-/// A wrapper type for a mutably borrowed value from an app data container.
-///
-/// This type is similar to [`RefMut`].
-pub struct AppDataRefMut<'a, T: ?Sized + 'a> {
-    data: RefMut<'a, T>,
-    borrow: &'a Cell<usize>,
-}
-
-impl<T: ?Sized> Drop for AppDataRefMut<'_, T> {
-    fn drop(&mut self) {
-        self.borrow.set(self.borrow.get() - 1);
-    }
-}
-
-impl<T: ?Sized> Deref for AppDataRefMut<'_, T> {
-    type Target = T;
-
-    #[inline]
-    fn deref(&self) -> &Self::Target {
-        &self.data
-    }
-}
-
-impl<T: ?Sized> DerefMut for AppDataRefMut<'_, T> {
-    #[inline]
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        &mut self.data
-    }
-}
-
-impl<T: ?Sized + fmt::Display> fmt::Display for AppDataRefMut<'_, T> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        (**self).fmt(f)
-    }
-}
-
-impl<T: ?Sized + fmt::Debug> fmt::Debug for AppDataRefMut<'_, T> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        (**self).fmt(f)
-    }
-}
+#[cfg(any(feature = "luau", doc))]
+mod vector;
 
 #[cfg(test)]
 mod assertions {
     use super::*;
 
-    static_assertions::assert_impl_all!(RegistryKey: Send, Sync);
-    static_assertions::assert_not_impl_any!(LuaRef: Send);
-
-    #[cfg(feature = "unstable")]
-    static_assertions::assert_not_impl_any!(LuaOwnedRef: Send);
+    #[cfg(not(feature = "send"))]
+    static_assertions::assert_not_impl_any!(ValueRef: Send);
+    #[cfg(feature = "send")]
+    static_assertions::assert_impl_all!(ValueRef: Send, Sync);
 }

src/types/app_data.rs

@@ -0,0 +1,176 @@
+use std::any::{Any, TypeId};
+use std::cell::{Cell, Ref, RefCell, RefMut, UnsafeCell};
+use std::fmt;
+use std::ops::{Deref, DerefMut};
+use std::result::Result as StdResult;
+
+use rustc_hash::FxHashMap;
+
+use super::MaybeSend;
+use crate::state::LuaGuard;
+
+#[cfg(not(feature = "send"))]
+type Container = UnsafeCell<FxHashMap<TypeId, RefCell<Box<dyn Any>>>>;
+
+#[cfg(feature = "send")]
+type Container = UnsafeCell<FxHashMap<TypeId, RefCell<Box<dyn Any + Send>>>>;
+
+/// A container for arbitrary data associated with the Lua state.
+#[derive(Debug, Default)]
+pub struct AppData {
+    container: Container,
+    borrow: Cell<usize>,
+}
+
+impl AppData {
+    #[track_caller]
+    pub(crate) fn insert<T: MaybeSend + 'static>(&self, data: T) -> Option<T> {
+        match self.try_insert(data) {
+            Ok(data) => data,
+            Err(_) => panic!("cannot mutably borrow app data container"),
+        }
+    }
+
+    pub(crate) fn try_insert<T: MaybeSend + 'static>(&self, data: T) -> StdResult<Option<T>, T> {
+        if self.borrow.get() != 0 {
+            return Err(data);
+        }
+        // SAFETY: we checked that there are no other references to the container
+        Ok(unsafe { &mut *self.container.get() }
+            .insert(TypeId::of::<T>(), RefCell::new(Box::new(data)))
+            .and_then(|data| data.into_inner().downcast::<T>().ok().map(|data| *data)))
+    }
+
+    #[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,
+        })
+    }
+
+    #[track_caller]
+    pub(crate) fn borrow_mut<T: 'static>(&self, guard: Option<LuaGuard>) -> Option<AppDataRefMut<T>> {
+        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,
+        })
+    }
+
+    #[track_caller]
+    pub(crate) fn remove<T: 'static>(&self) -> Option<T> {
+        if self.borrow.get() != 0 {
+            panic!("cannot mutably borrow app data container");
+        }
+        // SAFETY: we checked that there are no other references to the container
+        unsafe { &mut *self.container.get() }
+            .remove(&TypeId::of::<T>())?
+            .into_inner()
+            .downcast::<T>()
+            .ok()
+            .map(|data| *data)
+    }
+}
+
+/// A wrapper type for an immutably borrowed value from an app data container.
+///
+/// This type is similar to [`Ref`].
+pub struct AppDataRef<'a, T: ?Sized + 'a> {
+    data: Ref<'a, T>,
+    borrow: &'a Cell<usize>,
+    _guard: Option<LuaGuard>,
+}
+
+impl<T: ?Sized> Drop for AppDataRef<'_, T> {
+    fn drop(&mut self) {
+        self.borrow.set(self.borrow.get() - 1);
+    }
+}
+
+impl<T: ?Sized> Deref for AppDataRef<'_, T> {
+    type Target = T;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &self.data
+    }
+}
+
+impl<T: ?Sized + fmt::Display> fmt::Display for AppDataRef<'_, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
+impl<T: ?Sized + fmt::Debug> fmt::Debug for AppDataRef<'_, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
+/// A wrapper type for a mutably borrowed value from an app data container.
+///
+/// This type is similar to [`RefMut`].
+pub struct AppDataRefMut<'a, T: ?Sized + 'a> {
+    data: RefMut<'a, T>,
+    borrow: &'a Cell<usize>,
+    _guard: Option<LuaGuard>,
+}
+
+impl<T: ?Sized> Drop for AppDataRefMut<'_, T> {
+    fn drop(&mut self) {
+        self.borrow.set(self.borrow.get() - 1);
+    }
+}
+
+impl<T: ?Sized> Deref for AppDataRefMut<'_, T> {
+    type Target = T;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &self.data
+    }
+}
+
+impl<T: ?Sized> DerefMut for AppDataRefMut<'_, T> {
+    #[inline]
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.data
+    }
+}
+
+impl<T: ?Sized + fmt::Display> fmt::Display for AppDataRefMut<'_, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
+impl<T: ?Sized + fmt::Debug> fmt::Debug for AppDataRefMut<'_, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
+#[cfg(test)]
+mod assertions {
+    use super::*;
+
+    #[cfg(not(feature = "send"))]
+    static_assertions::assert_not_impl_any!(AppData: Send);
+    #[cfg(feature = "send")]
+    static_assertions::assert_impl_all!(AppData: Send);
+
+    // Must be !Send
+    static_assertions::assert_not_impl_any!(AppDataRef<()>: Send);
+    static_assertions::assert_not_impl_any!(AppDataRefMut<()>: Send);
+}

src/types/registry_key.rs

@@ -0,0 +1,101 @@
+use std::hash::{Hash, Hasher};
+use std::os::raw::c_int;
+use std::sync::Arc;
+use std::{fmt, mem, ptr};
+
+use parking_lot::Mutex;
+
+/// An auto generated key into the Lua registry.
+///
+/// This is a handle to a value stored inside the Lua registry. It is not automatically
+/// garbage collected on Drop, but it can be removed with [`Lua::remove_registry_value`],
+/// 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`].
+///
+/// [`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>>>>,
+}
+
+impl fmt::Debug for RegistryKey {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "RegistryKey({})", self.id())
+    }
+}
+
+impl Hash for RegistryKey {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.id().hash(state)
+    }
+}
+
+impl PartialEq for RegistryKey {
+    fn eq(&self, other: &RegistryKey) -> bool {
+        self.id() == other.id() && Arc::ptr_eq(&self.unref_list, &other.unref_list)
+    }
+}
+
+impl Eq for RegistryKey {}
+
+impl Drop for RegistryKey {
+    fn drop(&mut self) {
+        let registry_id = self.id();
+        // We don't need to collect nil slot
+        if registry_id > ffi::LUA_REFNIL {
+            let mut unref_list = self.unref_list.lock();
+            if let Some(list) = unref_list.as_mut() {
+                list.push(registry_id);
+            }
+        }
+    }
+}
+
+impl RegistryKey {
+    /// Creates a new instance of `RegistryKey`
+    pub(crate) const fn new(id: c_int, unref_list: Arc<Mutex<Option<Vec<c_int>>>>) -> Self {
+        RegistryKey {
+            registry_id: id,
+            unref_list,
+        }
+    }
+
+    /// Returns the underlying Lua reference of this `RegistryKey`
+    #[inline(always)]
+    pub fn id(&self) -> c_int {
+        self.registry_id
+    }
+
+    /// Sets the unique Lua reference key of this `RegistryKey`
+    #[inline(always)]
+    pub(crate) fn set_id(&mut self, id: c_int) {
+        self.registry_id = id;
+    }
+
+    /// Destroys the `RegistryKey` without adding to the unref list
+    pub(crate) fn take(self) -> i32 {
+        let registry_id = self.id();
+        unsafe {
+            ptr::read(&self.unref_list);
+            mem::forget(self);
+        }
+        registry_id
+    }
+}
+
+#[cfg(test)]
+mod assertions {
+    use super::*;
+
+    static_assertions::assert_impl_all!(RegistryKey: Send, Sync);
+}

src/types/sync.rs

@@ -0,0 +1,77 @@
+#[cfg(feature = "send")]
+mod inner {
+    use parking_lot::{RawMutex, RawThreadId};
+    use std::sync::{Arc, Weak};
+
+    pub(crate) type XRc<T> = Arc<T>;
+    pub(crate) type XWeak<T> = Weak<T>;
+
+    pub(crate) type ReentrantMutex<T> = parking_lot::ReentrantMutex<T>;
+
+    pub(crate) type ReentrantMutexGuard<'a, T> = parking_lot::ReentrantMutexGuard<'a, T>;
+
+    pub(crate) type ArcReentrantMutexGuard<T> =
+        parking_lot::lock_api::ArcReentrantMutexGuard<RawMutex, RawThreadId, T>;
+}
+
+#[cfg(not(feature = "send"))]
+mod inner {
+    use std::ops::Deref;
+    use std::rc::{Rc, Weak};
+
+    pub(crate) type XRc<T> = Rc<T>;
+    pub(crate) type XWeak<T> = Weak<T>;
+
+    pub(crate) struct ReentrantMutex<T>(T);
+
+    impl<T> ReentrantMutex<T> {
+        #[inline(always)]
+        pub(crate) fn new(val: T) -> Self {
+            ReentrantMutex(val)
+        }
+
+        #[inline(always)]
+        pub(crate) fn lock(&self) -> ReentrantMutexGuard<T> {
+            ReentrantMutexGuard(&self.0)
+        }
+
+        #[inline(always)]
+        pub(crate) fn lock_arc(self: &XRc<Self>) -> ArcReentrantMutexGuard<T> {
+            ArcReentrantMutexGuard(Rc::clone(self))
+        }
+
+        #[inline(always)]
+        pub(crate) fn into_lock_arc(self: XRc<Self>) -> ArcReentrantMutexGuard<T> {
+            ArcReentrantMutexGuard(self)
+        }
+
+        #[inline(always)]
+        pub(crate) fn data_ptr(&self) -> *const T {
+            &self.0 as *const _
+        }
+    }
+
+    pub(crate) struct ReentrantMutexGuard<'a, T>(&'a T);
+
+    impl<'a, T> Deref for ReentrantMutexGuard<'a, T> {
+        type Target = T;
+
+        #[inline(always)]
+        fn deref(&self) -> &Self::Target {
+            self.0
+        }
+    }
+
+    pub(crate) struct ArcReentrantMutexGuard<T>(XRc<ReentrantMutex<T>>);
+
+    impl<T> Deref for ArcReentrantMutexGuard<T> {
+        type Target = T;
+
+        #[inline(always)]
+        fn deref(&self) -> &Self::Target {
+            &self.0 .0
+        }
+    }
+}
+
+pub(crate) use inner::{ArcReentrantMutexGuard, ReentrantMutex, ReentrantMutexGuard, XRc, XWeak};

src/types/vector.rs

@@ -0,0 +1,86 @@
+use std::fmt;
+
+#[cfg(all(any(feature = "luau", doc), feature = "serialize"))]
+use serde::ser::{Serialize, SerializeTupleStruct, Serializer};
+
+/// A Luau vector type.
+///
+/// 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)]
+pub struct Vector(pub(crate) [f32; Self::SIZE]);
+
+impl fmt::Display for Vector {
+    #[rustfmt::skip]
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        #[cfg(not(feature = "luau-vector4"))]
+        return write!(f, "vector({}, {}, {})", self.x(), self.y(), self.z());
+        #[cfg(feature = "luau-vector4")]
+        return write!(f, "vector({}, {}, {}, {})", self.x(), self.y(), self.z(), self.w());
+    }
+}
+
+impl Vector {
+    pub(crate) const SIZE: usize = if cfg!(feature = "luau-vector4") { 4 } else { 3 };
+
+    /// Creates a new vector.
+    #[cfg(not(feature = "luau-vector4"))]
+    pub const fn new(x: f32, y: f32, z: f32) -> Self {
+        Self([x, y, z])
+    }
+
+    /// Creates a new vector.
+    #[cfg(feature = "luau-vector4")]
+    pub const fn new(x: f32, y: f32, z: f32, w: f32) -> Self {
+        Self([x, y, z, w])
+    }
+
+    /// Creates a new vector with all components set to `0.0`.
+    #[doc(hidden)]
+    pub const fn zero() -> Self {
+        Self([0.0; Self::SIZE])
+    }
+
+    /// Returns 1st component of the vector.
+    pub const fn x(&self) -> f32 {
+        self.0[0]
+    }
+
+    /// Returns 2nd component of the vector.
+    pub const fn y(&self) -> f32 {
+        self.0[1]
+    }
+
+    /// Returns 3rd component of the vector.
+    pub const fn z(&self) -> f32 {
+        self.0[2]
+    }
+
+    /// Returns 4th component of the vector.
+    #[cfg(any(feature = "luau-vector4", doc))]
+    #[cfg_attr(docsrs, doc(cfg(feature = "luau-vector4")))]
+    pub const fn w(&self) -> f32 {
+        self.0[3]
+    }
+}
+
+#[cfg(all(any(feature = "luau", doc), feature = "serialize"))]
+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)?;
+        ts.serialize_field(&self.x())?;
+        ts.serialize_field(&self.y())?;
+        ts.serialize_field(&self.z())?;
+        #[cfg(feature = "luau-vector4")]
+        ts.serialize_field(&self.w())?;
+        ts.end()
+    }
+}
+
+impl PartialEq<[f32; Self::SIZE]> for Vector {
+    #[inline]
+    fn eq(&self, other: &[f32; Self::SIZE]) -> bool {
+        self.0 == *other
+    }
+}

src/userdata/cell.rs

@@ -0,0 +1,391 @@
+use std::any::{type_name, TypeId};
+use std::cell::UnsafeCell;
+use std::fmt;
+use std::ops::{Deref, DerefMut};
+use std::os::raw::c_int;
+
+#[cfg(feature = "serialize")]
+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 super::lock::{RawLock, UserDataLock};
+
+#[cfg(all(feature = "serialize", not(feature = "send")))]
+type DynSerialize = dyn erased_serde::Serialize;
+
+#[cfg(all(feature = "serialize", feature = "send"))]
+type DynSerialize = dyn erased_serde::Serialize + Send;
+
+// 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>>>),
+}
+
+impl<T> Clone for UserDataVariant<T> {
+    #[inline]
+    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)),
+        }
+    }
+}
+
+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())
+    }
+
+    // Mutably borrows the wrapped value in-place.
+    #[inline(always)]
+    pub(crate) fn try_borrow_mut(&self) -> Result<UserDataBorrowMut<T>> {
+        UserDataBorrowMut::try_from(self)
+    }
+
+    // Mutably borrows the wrapped value and returns an owned reference.
+    #[inline(always)]
+    pub(crate) 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> {
+        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 {
+                let raw = Box::into_raw(XRc::into_inner(inner).unwrap().value.into_inner());
+                *Box::from_raw(raw as *mut T)
+            },
+        })
+    }
+
+    #[inline(always)]
+    fn raw_lock(&self) -> &RawLock {
+        match self {
+            Self::Default(inner) => &inner.raw_lock,
+            #[cfg(feature = "serialize")]
+            Self::Serializable(inner) => &inner.raw_lock,
+        }
+    }
+
+    #[inline(always)]
+    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 = "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<()> {
+    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.
+                #[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.
+                #[cfg(not(feature = "send"))]
+                let _guard = self.try_borrow().map_err(serde::ser::Error::custom)?;
+                (*inner.value.get()).serialize(serializer)
+            },
+        }
+    }
+}
+
+/// A type that provides interior mutability for a userdata value (thread-safe).
+pub(crate) struct UserDataCell<T> {
+    raw_lock: RawLock,
+    value: UnsafeCell<T>,
+}
+
+unsafe impl<T: Send> Send for UserDataCell<T> {}
+unsafe impl<T: Send> Sync for UserDataCell<T> {}
+
+impl<T> UserDataCell<T> {
+    #[inline(always)]
+    pub fn new(value: T) -> Self {
+        UserDataCell {
+            raw_lock: RawLock::INIT,
+            value: UnsafeCell::new(value),
+        }
+    }
+}
+
+/// 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() }
+    }
+}
+
+impl<T> Drop for UserDataRef<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()
+            }
+            _ => 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> 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) 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);
+        }
+        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>())),
+        }),
+    }
+}
+
+#[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

@@ -0,0 +1,93 @@
+pub(crate) trait UserDataLock {
+    const INIT: Self;
+
+    fn try_lock_shared(&self) -> bool;
+    fn try_lock_exclusive(&self) -> bool;
+
+    unsafe fn unlock_shared(&self);
+    unsafe fn unlock_exclusive(&self);
+}
+
+pub(crate) use lock_impl::RawLock;
+
+#[cfg(not(feature = "send"))]
+mod lock_impl {
+    use std::cell::Cell;
+
+    // Positive values represent the number of read references.
+    // Negative values represent the number of write references (only one allowed).
+    pub(crate) type RawLock = Cell<isize>;
+
+    const UNUSED: isize = 0;
+
+    impl super::UserDataLock for RawLock {
+        #[allow(clippy::declare_interior_mutable_const)]
+        const INIT: Self = Cell::new(UNUSED);
+
+        #[inline(always)]
+        fn try_lock_shared(&self) -> bool {
+            let flag = self.get().wrapping_add(1);
+            if flag <= UNUSED {
+                return false;
+            }
+            self.set(flag);
+            true
+        }
+
+        #[inline(always)]
+        fn try_lock_exclusive(&self) -> bool {
+            let flag = self.get();
+            if flag != UNUSED {
+                return false;
+            }
+            self.set(UNUSED - 1);
+            true
+        }
+
+        #[inline(always)]
+        unsafe fn unlock_shared(&self) {
+            let flag = self.get();
+            debug_assert!(flag > UNUSED);
+            self.set(flag - 1);
+        }
+
+        #[inline(always)]
+        unsafe fn unlock_exclusive(&self) {
+            let flag = self.get();
+            debug_assert!(flag < UNUSED);
+            self.set(flag + 1);
+        }
+    }
+}
+
+#[cfg(feature = "send")]
+mod lock_impl {
+    use parking_lot::lock_api::RawMutex;
+
+    pub(crate) type RawLock = parking_lot::RawMutex;
+
+    impl super::UserDataLock for RawLock {
+        #[allow(clippy::declare_interior_mutable_const)]
+        const INIT: Self = <Self as parking_lot::lock_api::RawMutex>::INIT;
+
+        #[inline(always)]
+        fn try_lock_shared(&self) -> bool {
+            RawLock::try_lock(self)
+        }
+
+        #[inline(always)]
+        fn try_lock_exclusive(&self) -> bool {
+            RawLock::try_lock(self)
+        }
+
+        #[inline(always)]
+        unsafe fn unlock_shared(&self) {
+            RawLock::unlock(self)
+        }
+
+        #[inline(always)]
+        unsafe fn unlock_exclusive(&self) {
+            RawLock::unlock(self)
+        }
+    }
+}

src/userdata/object.rs

@@ -0,0 +1,93 @@
+use std::string::String as StdString;
+
+use crate::error::{Error, Result};
+use crate::table::Table;
+use crate::traits::ObjectLike;
+use crate::userdata::AnyUserData;
+use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, Value};
+use crate::Function;
+
+#[cfg(feature = "async")]
+use futures_util::future::{self, Either, Future};
+
+impl ObjectLike for AnyUserData {
+    #[inline]
+    fn get<V: FromLua>(&self, key: impl IntoLua) -> Result<V> {
+        // `lua_gettable` method used under the hood can work with any Lua value
+        // that has `__index` metamethod
+        Table(self.0.copy()).get_protected(key)
+    }
+
+    #[inline]
+    fn set(&self, key: impl IntoLua, value: impl IntoLua) -> Result<()> {
+        // `lua_settable` method used under the hood can work with any Lua value
+        // that has `__newindex` metamethod
+        Table(self.0.copy()).set_protected(key, value)
+    }
+
+    #[inline]
+    fn call<R>(&self, args: impl IntoLuaMulti) -> Result<R>
+    where
+        R: FromLuaMulti,
+    {
+        Function(self.0.copy()).call(args)
+    }
+
+    #[cfg(feature = "async")]
+    #[inline]
+    fn call_async<R>(&self, args: impl IntoLuaMulti) -> impl Future<Output = Result<R>>
+    where
+        R: FromLuaMulti,
+    {
+        Function(self.0.copy()).call_async(args)
+    }
+
+    #[inline]
+    fn call_method<R>(&self, name: &str, args: impl IntoLuaMulti) -> Result<R>
+    where
+        R: FromLuaMulti,
+    {
+        self.call_function(name, (self, args))
+    }
+
+    #[cfg(feature = "async")]
+    fn call_async_method<R>(&self, name: &str, args: impl IntoLuaMulti) -> impl Future<Output = Result<R>>
+    where
+        R: FromLuaMulti,
+    {
+        self.call_async_function(name, (self, args))
+    }
+
+    fn call_function<R>(&self, name: &str, args: impl IntoLuaMulti) -> Result<R>
+    where
+        R: FromLuaMulti,
+    {
+        match self.get(name)? {
+            Value::Function(func) => func.call(args),
+            val => {
+                let msg = format!("attempt to call a {} value (function '{name}')", val.type_name());
+                Err(Error::RuntimeError(msg))
+            }
+        }
+    }
+
+    #[cfg(feature = "async")]
+    fn call_async_function<R>(&self, name: &str, args: impl IntoLuaMulti) -> impl Future<Output = Result<R>>
+    where
+        R: FromLuaMulti,
+    {
+        match self.get(name) {
+            Ok(Value::Function(func)) => Either::Left(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))))
+            }
+            Err(err) => Either::Right(future::ready(Err(err))),
+        }
+    }
+
+    #[inline]
+    fn to_string(&self) -> Result<StdString> {
+        Value::UserData(AnyUserData(self.0.copy(), self.1)).to_string()
+    }
+}

src/userdata/registry.rs

@@ -0,0 +1,582 @@
+#![allow(clippy::await_holding_refcell_ref, clippy::await_holding_lock)]
+
+use std::any::TypeId;
+use std::cell::RefCell;
+use std::marker::PhantomData;
+use std::os::raw::c_int;
+use std::string::String as StdString;
+
+use crate::error::{Error, Result};
+use crate::state::{Lua, RawLua};
+use crate::types::{Callback, MaybeSend};
+use crate::userdata::{
+    AnyUserData, MetaMethod, UserData, UserDataFields, UserDataMethods, UserDataRef, UserDataRefMut,
+};
+use crate::util::{get_userdata, short_type_name};
+use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, Value};
+
+use super::cell::{UserDataBorrowMut, UserDataBorrowRef, UserDataVariant};
+
+#[cfg(feature = "async")]
+use {
+    crate::types::AsyncCallback,
+    std::future::{self, Future},
+};
+
+type StaticFieldCallback = Box<dyn FnOnce(&RawLua) -> Result<()> + 'static>;
+
+/// Handle to registry for userdata methods and metamethods.
+pub struct UserDataRegistry<T: 'static> {
+    // Fields
+    pub(crate) fields: Vec<(String, StaticFieldCallback)>,
+    pub(crate) field_getters: Vec<(String, Callback)>,
+    pub(crate) field_setters: Vec<(String, Callback)>,
+    pub(crate) meta_fields: Vec<(String, StaticFieldCallback)>,
+
+    // Methods
+    pub(crate) methods: Vec<(String, Callback)>,
+    #[cfg(feature = "async")]
+    pub(crate) async_methods: Vec<(String, AsyncCallback)>,
+    pub(crate) meta_methods: Vec<(String, Callback)>,
+    #[cfg(feature = "async")]
+    pub(crate) async_meta_methods: Vec<(String, AsyncCallback)>,
+
+    _type: PhantomData<T>,
+}
+
+impl<T: 'static> UserDataRegistry<T> {
+    pub(crate) const fn new() -> Self {
+        UserDataRegistry {
+            fields: Vec::new(),
+            field_getters: Vec::new(),
+            field_setters: Vec::new(),
+            meta_fields: Vec::new(),
+            methods: Vec::new(),
+            #[cfg(feature = "async")]
+            async_methods: Vec::new(),
+            meta_methods: Vec::new(),
+            #[cfg(feature = "async")]
+            async_meta_methods: Vec::new(),
+            _type: PhantomData,
+        }
+    }
+
+    fn box_method<M, A, R>(name: &str, method: M) -> Callback
+    where
+        M: Fn(&Lua, &T, A) -> Result<R> + MaybeSend + 'static,
+        A: FromLuaMulti,
+        R: IntoLuaMulti,
+    {
+        let name = get_function_name::<T>(name);
+        macro_rules! try_self_arg {
+            ($res:expr) => {
+                $res.map_err(|err| Error::bad_self_argument(&name, err))?
+            };
+        }
+
+        Box::new(move |rawlua, nargs| unsafe {
+            if nargs == 0 {
+                let err = Error::from_lua_conversion("missing argument", "userdata", None);
+                try_self_arg!(Err(err));
+            }
+            let state = rawlua.state();
+            // Find absolute "self" index before processing args
+            let self_index = ffi::lua_absindex(state, -nargs);
+            // Self was at position 1, so we pass 2 here
+            let args = A::from_stack_args(nargs - 1, 2, Some(&name), rawlua);
+
+            match try_self_arg!(rawlua.get_userdata_type_id(self_index)) {
+                Some(id) if id == TypeId::of::<T>() => {
+                    let ud = try_self_arg!(borrow_userdata_ref::<T>(state, self_index));
+                    method(rawlua.lua(), &ud, args?)?.push_into_stack_multi(rawlua)
+                }
+                _ => Err(Error::bad_self_argument(&name, Error::UserDataTypeMismatch)),
+            }
+        })
+    }
+
+    fn box_method_mut<M, A, R>(name: &str, method: M) -> Callback
+    where
+        M: FnMut(&Lua, &mut T, A) -> Result<R> + MaybeSend + 'static,
+        A: FromLuaMulti,
+        R: IntoLuaMulti,
+    {
+        let name = get_function_name::<T>(name);
+        macro_rules! try_self_arg {
+            ($res:expr) => {
+                $res.map_err(|err| Error::bad_self_argument(&name, err))?
+            };
+        }
+
+        let method = RefCell::new(method);
+        Box::new(move |rawlua, nargs| unsafe {
+            let mut method = method.try_borrow_mut().map_err(|_| Error::RecursiveMutCallback)?;
+            if nargs == 0 {
+                let err = Error::from_lua_conversion("missing argument", "userdata", None);
+                try_self_arg!(Err(err));
+            }
+            let state = rawlua.state();
+            // Find absolute "self" index before processing args
+            let self_index = ffi::lua_absindex(state, -nargs);
+            // Self was at position 1, so we pass 2 here
+            let args = A::from_stack_args(nargs - 1, 2, Some(&name), rawlua);
+
+            match try_self_arg!(rawlua.get_userdata_type_id(self_index)) {
+                Some(id) if id == TypeId::of::<T>() => {
+                    let mut ud = try_self_arg!(borrow_userdata_mut::<T>(state, self_index));
+                    method(rawlua.lua(), &mut ud, args?)?.push_into_stack_multi(rawlua)
+                }
+                _ => Err(Error::bad_self_argument(&name, Error::UserDataTypeMismatch)),
+            }
+        })
+    }
+
+    #[cfg(feature = "async")]
+    fn box_async_method<M, A, MR, R>(name: &str, method: M) -> AsyncCallback
+    where
+        M: Fn(Lua, UserDataRef<T>, A) -> MR + MaybeSend + 'static,
+        A: FromLuaMulti,
+        MR: Future<Output = Result<R>> + MaybeSend + 'static,
+        R: IntoLuaMulti,
+    {
+        let name = get_function_name::<T>(name);
+        macro_rules! try_self_arg {
+            ($res:expr) => {
+                match $res {
+                    Ok(res) => res,
+                    Err(err) => return Box::pin(future::ready(Err(Error::bad_self_argument(&name, err)))),
+                }
+            };
+        }
+
+        Box::new(move |rawlua, nargs| unsafe {
+            if nargs == 0 {
+                let err = Error::from_lua_conversion("missing argument", "userdata", None);
+                try_self_arg!(Err(err));
+            }
+            // Stack will be empty when polling the future, keep `self` on the ref thread
+            let self_ud = try_self_arg!(AnyUserData::from_stack(-nargs, rawlua));
+            let args = A::from_stack_args(nargs - 1, 2, Some(&name), rawlua);
+
+            let self_ud = try_self_arg!(self_ud.borrow());
+            let args = match args {
+                Ok(args) => args,
+                Err(e) => return Box::pin(future::ready(Err(e))),
+            };
+            let lua = rawlua.lua();
+            let fut = method(lua.clone(), self_ud, args);
+            // Lua is locked when the future is polled
+            Box::pin(async move { fut.await?.push_into_stack_multi(lua.raw_lua()) })
+        })
+    }
+
+    #[cfg(feature = "async")]
+    fn box_async_method_mut<M, A, MR, R>(name: &str, method: M) -> AsyncCallback
+    where
+        M: Fn(Lua, UserDataRefMut<T>, A) -> MR + MaybeSend + 'static,
+        A: FromLuaMulti,
+        MR: Future<Output = Result<R>> + MaybeSend + 'static,
+        R: IntoLuaMulti,
+    {
+        let name = get_function_name::<T>(name);
+        macro_rules! try_self_arg {
+            ($res:expr) => {
+                match $res {
+                    Ok(res) => res,
+                    Err(err) => return Box::pin(future::ready(Err(Error::bad_self_argument(&name, err)))),
+                }
+            };
+        }
+
+        Box::new(move |rawlua, nargs| unsafe {
+            if nargs == 0 {
+                let err = Error::from_lua_conversion("missing argument", "userdata", None);
+                try_self_arg!(Err(err));
+            }
+            // Stack will be empty when polling the future, keep `self` on the ref thread
+            let self_ud = try_self_arg!(AnyUserData::from_stack(-nargs, rawlua));
+            let args = A::from_stack_args(nargs - 1, 2, Some(&name), rawlua);
+
+            let self_ud = try_self_arg!(self_ud.borrow_mut());
+            let args = match args {
+                Ok(args) => args,
+                Err(e) => return Box::pin(future::ready(Err(e))),
+            };
+            let lua = rawlua.lua();
+            let fut = method(lua.clone(), self_ud, args);
+            // Lua is locked when the future is polled
+            Box::pin(async move { fut.await?.push_into_stack_multi(lua.raw_lua()) })
+        })
+    }
+
+    fn box_function<F, A, R>(name: &str, function: F) -> Callback
+    where
+        F: Fn(&Lua, A) -> Result<R> + MaybeSend + 'static,
+        A: FromLuaMulti,
+        R: IntoLuaMulti,
+    {
+        let name = get_function_name::<T>(name);
+        Box::new(move |lua, nargs| unsafe {
+            let args = A::from_stack_args(nargs, 1, Some(&name), lua)?;
+            function(lua.lua(), args)?.push_into_stack_multi(lua)
+        })
+    }
+
+    fn box_function_mut<F, A, R>(name: &str, function: F) -> Callback
+    where
+        F: FnMut(&Lua, A) -> Result<R> + MaybeSend + 'static,
+        A: FromLuaMulti,
+        R: IntoLuaMulti,
+    {
+        let name = get_function_name::<T>(name);
+        let function = RefCell::new(function);
+        Box::new(move |lua, nargs| unsafe {
+            let function = &mut *function
+                .try_borrow_mut()
+                .map_err(|_| Error::RecursiveMutCallback)?;
+            let args = A::from_stack_args(nargs, 1, Some(&name), lua)?;
+            function(lua.lua(), args)?.push_into_stack_multi(lua)
+        })
+    }
+
+    #[cfg(feature = "async")]
+    fn box_async_function<F, A, FR, R>(name: &str, function: F) -> AsyncCallback
+    where
+        F: Fn(Lua, A) -> FR + MaybeSend + 'static,
+        A: FromLuaMulti,
+        FR: Future<Output = Result<R>> + MaybeSend + 'static,
+        R: IntoLuaMulti,
+    {
+        let name = get_function_name::<T>(name);
+        Box::new(move |rawlua, nargs| unsafe {
+            let args = match A::from_stack_args(nargs, 1, Some(&name), rawlua) {
+                Ok(args) => args,
+                Err(e) => return Box::pin(future::ready(Err(e))),
+            };
+            let lua = rawlua.lua();
+            let fut = function(lua.clone(), args);
+            Box::pin(async move { fut.await?.push_into_stack_multi(lua.raw_lua()) })
+        })
+    }
+
+    pub(crate) fn check_meta_field(lua: &Lua, name: &str, value: impl IntoLua) -> Result<Value> {
+        let value = value.into_lua(lua)?;
+        if name == MetaMethod::Index || name == MetaMethod::NewIndex {
+            match value {
+                Value::Nil | Value::Table(_) | Value::Function(_) => {}
+                _ => {
+                    return Err(Error::MetaMethodTypeError {
+                        method: name.to_string(),
+                        type_name: value.type_name(),
+                        message: Some("expected nil, table or function".to_string()),
+                    })
+                }
+            }
+        }
+        value.into_lua(lua)
+    }
+}
+
+// Returns function name for the type `T`, without the module path
+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)
+    where
+        V: IntoLua + 'static,
+    {
+        let name = name.to_string();
+        self.fields.push((
+            name,
+            Box::new(move |rawlua| unsafe { value.push_into_stack(rawlua) }),
+        ));
+    }
+
+    fn add_field_method_get<M, R>(&mut self, name: impl ToString, 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));
+    }
+
+    fn add_field_method_set<M, A>(&mut self, name: impl ToString, 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));
+    }
+
+    fn add_field_function_get<F, R>(&mut self, name: impl ToString, 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));
+    }
+
+    fn add_field_function_set<F, A>(&mut self, name: impl ToString, 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));
+    }
+
+    fn add_meta_field<V>(&mut self, name: impl ToString, 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)
+            }),
+        ));
+    }
+
+    fn add_meta_field_with<F, R>(&mut self, name: impl ToString, 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)
+            }),
+        ));
+    }
+}
+
+impl<T: 'static> UserDataMethods<T> for UserDataRegistry<T> {
+    fn add_method<M, A, R>(&mut self, name: impl ToString, 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));
+    }
+
+    fn add_method_mut<M, A, R>(&mut self, name: impl ToString, 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));
+    }
+
+    #[cfg(feature = "async")]
+    fn add_async_method<M, A, MR, R>(&mut self, name: impl ToString, method: M)
+    where
+        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));
+    }
+
+    #[cfg(feature = "async")]
+    fn add_async_method_mut<M, A, MR, R>(&mut self, name: impl ToString, method: M)
+    where
+        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));
+    }
+
+    fn add_function<F, A, R>(&mut self, name: impl ToString, 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));
+    }
+
+    fn add_function_mut<F, A, R>(&mut self, name: impl ToString, 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));
+    }
+
+    #[cfg(feature = "async")]
+    fn add_async_function<F, A, FR, R>(&mut self, name: impl ToString, 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));
+    }
+
+    fn add_meta_method<M, A, R>(&mut self, name: impl ToString, 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));
+    }
+
+    fn add_meta_method_mut<M, A, R>(&mut self, name: impl ToString, 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));
+    }
+
+    #[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)
+    where
+        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));
+    }
+
+    #[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)
+    where
+        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));
+    }
+
+    fn add_meta_function<F, A, R>(&mut self, name: impl ToString, 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));
+    }
+
+    fn add_meta_function_mut<F, A, R>(&mut self, name: impl ToString, 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));
+    }
+
+    #[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)
+    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));
+    }
+}
+
+// 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();
+                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);
+                #[cfg(feature = "async")]
+                registry.async_methods.extend(orig_registry.async_methods);
+                registry.meta_methods.extend(orig_registry.meta_methods);
+                #[cfg(feature = "async")]
+                registry
+                    .async_meta_methods
+                    .extend(orig_registry.async_meta_methods);
+            }
+        }
+    };
+}
+
+// A special proxy object for UserData
+pub(crate) struct UserDataProxy<T>(pub(crate) PhantomData<T>);
+
+lua_userdata_impl!(UserDataProxy<T>);

src/userdata_ext.rs

@@ -1,190 +0,0 @@
-use crate::error::{Error, Result};
-use crate::private::Sealed;
-use crate::userdata::{AnyUserData, MetaMethod};
-use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, Value};
-
-#[cfg(feature = "async")]
-use futures_util::future::{self, LocalBoxFuture};
-
-/// An extension trait for [`AnyUserData`] that provides a variety of convenient functionality.
-pub trait AnyUserDataExt<'lua>: Sealed {
-    /// Gets the value associated to `key` from the userdata, assuming it has `__index` metamethod.
-    fn get<K: IntoLua<'lua>, V: FromLua<'lua>>(&self, key: K) -> Result<V>;
-
-    /// Sets the value associated to `key` in the userdata, assuming it has `__newindex` metamethod.
-    fn set<K: IntoLua<'lua>, V: IntoLua<'lua>>(&self, key: K, value: V) -> Result<()>;
-
-    /// Calls the userdata as a function assuming it has `__call` metamethod.
-    ///
-    /// The metamethod is called with the userdata as its first argument, followed by the passed arguments.
-    fn call<A, R>(&self, args: A) -> Result<R>
-    where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua>;
-
-    /// Asynchronously calls the userdata as a function assuming it has `__call` metamethod.
-    ///
-    /// The metamethod is called with the userdata as its first argument, followed by the passed arguments.
-    #[cfg(feature = "async")]
-    #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
-    fn call_async<A, R>(&self, args: A) -> LocalBoxFuture<'lua, Result<R>>
-    where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua;
-
-    /// Calls the userdata method, assuming it has `__index` metamethod
-    /// and a function associated to `name`.
-    fn call_method<A, R>(&self, name: &str, args: A) -> Result<R>
-    where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua>;
-
-    /// Gets the function associated to `key` from the table and asynchronously executes it,
-    /// passing the table itself along with `args` as function arguments and returning Future.
-    ///
-    /// Requires `feature = "async"`
-    ///
-    /// This might invoke the `__index` metamethod.
-    #[cfg(feature = "async")]
-    #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
-    fn call_async_method<A, R>(&self, name: &str, args: A) -> LocalBoxFuture<'lua, Result<R>>
-    where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua;
-
-    /// Gets the function associated to `key` from the table and executes it,
-    /// passing `args` as function arguments.
-    ///
-    /// This is a shortcut for
-    /// `table.get::<_, Function>(key)?.call(args)`
-    ///
-    /// This might invoke the `__index` metamethod.
-    fn call_function<A, R>(&self, name: &str, args: A) -> Result<R>
-    where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua>;
-
-    /// Gets the function associated to `key` from the table and asynchronously executes it,
-    /// passing `args` as function arguments and returning Future.
-    ///
-    /// Requires `feature = "async"`
-    ///
-    /// This might invoke the `__index` metamethod.
-    #[cfg(feature = "async")]
-    #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
-    fn call_async_function<A, R>(&self, name: &str, args: A) -> LocalBoxFuture<'lua, Result<R>>
-    where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua;
-}
-
-impl<'lua> AnyUserDataExt<'lua> for AnyUserData<'lua> {
-    fn get<K: IntoLua<'lua>, V: FromLua<'lua>>(&self, key: K) -> Result<V> {
-        let metatable = self.get_metatable()?;
-        match metatable.get::<Value>(MetaMethod::Index)? {
-            Value::Table(table) => table.raw_get(key),
-            Value::Function(func) => func.call((self.clone(), key)),
-            _ => Err(Error::runtime("attempt to index a userdata value")),
-        }
-    }
-
-    fn set<K: IntoLua<'lua>, V: IntoLua<'lua>>(&self, key: K, value: V) -> Result<()> {
-        let metatable = self.get_metatable()?;
-        match metatable.get::<Value>(MetaMethod::NewIndex)? {
-            Value::Table(table) => table.raw_set(key, value),
-            Value::Function(func) => func.call((self.clone(), key, value)),
-            _ => Err(Error::runtime("attempt to index a userdata value")),
-        }
-    }
-
-    fn call<A, R>(&self, args: A) -> Result<R>
-    where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua>,
-    {
-        let metatable = self.get_metatable()?;
-        match metatable.get::<Value>(MetaMethod::Call)? {
-            Value::Function(func) => func.call((self.clone(), args)),
-            _ => Err(Error::runtime("attempt to call a userdata value")),
-        }
-    }
-
-    #[cfg(feature = "async")]
-    fn call_async<A, R>(&self, args: A) -> LocalBoxFuture<'lua, Result<R>>
-    where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua,
-    {
-        let metatable = match self.get_metatable() {
-            Ok(metatable) => metatable,
-            Err(err) => return Box::pin(future::err(err)),
-        };
-        match metatable.get::<Value>(MetaMethod::Call) {
-            Ok(Value::Function(func)) => {
-                let mut args = match args.into_lua_multi(self.0.lua) {
-                    Ok(args) => args,
-                    Err(e) => return Box::pin(future::err(e)),
-                };
-                args.push_front(Value::UserData(self.clone()));
-                Box::pin(async move { func.call_async(args).await })
-            }
-            Ok(_) => Box::pin(future::err(Error::runtime(
-                "attempt to call a userdata value",
-            ))),
-            Err(err) => Box::pin(future::err(err)),
-        }
-    }
-
-    fn call_method<A, R>(&self, name: &str, args: A) -> Result<R>
-    where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua>,
-    {
-        self.call_function(name, (self.clone(), args))
-    }
-
-    #[cfg(feature = "async")]
-    fn call_async_method<A, R>(&self, name: &str, args: A) -> LocalBoxFuture<'lua, Result<R>>
-    where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua,
-    {
-        self.call_async_function(name, (self.clone(), args))
-    }
-
-    fn call_function<A, R>(&self, name: &str, args: A) -> Result<R>
-    where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua>,
-    {
-        match self.get(name)? {
-            Value::Function(func) => func.call(args),
-            val => {
-                let msg = format!("attempt to call a {} value", val.type_name());
-                Err(Error::runtime(msg))
-            }
-        }
-    }
-
-    #[cfg(feature = "async")]
-    fn call_async_function<A, R>(&self, name: &str, args: A) -> LocalBoxFuture<'lua, Result<R>>
-    where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua,
-    {
-        match self.get(name) {
-            Ok(Value::Function(func)) => {
-                let args = match args.into_lua_multi(self.0.lua) {
-                    Ok(args) => args,
-                    Err(e) => return Box::pin(future::err(e)),
-                };
-                Box::pin(async move { func.call_async(args).await })
-            }
-            Ok(val) => {
-                let msg = format!("attempt to call a {} value", val.type_name());
-                Box::pin(future::err(Error::runtime(msg)))
-            }
-            Err(err) => Box::pin(future::err(err)),
-        }
-    }
-}

src/userdata_impl.rs

@@ -1,797 +0,0 @@
-#![allow(clippy::await_holding_refcell_ref, clippy::await_holding_lock)]
-
-use std::any::TypeId;
-use std::cell::{Ref, RefCell, RefMut};
-use std::marker::PhantomData;
-use std::os::raw::c_int;
-use std::string::String as StdString;
-use std::sync::{Arc, Mutex, RwLock};
-
-use crate::error::{Error, Result};
-use crate::lua::Lua;
-use crate::types::{Callback, MaybeSend};
-use crate::userdata::{
-    AnyUserData, MetaMethod, UserData, UserDataCell, UserDataFields, UserDataMethods,
-};
-use crate::util::{get_userdata, short_type_name};
-use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, Value};
-
-#[cfg(not(feature = "send"))]
-use std::rc::Rc;
-
-#[cfg(feature = "async")]
-use {crate::types::AsyncCallback, futures_util::future, std::future::Future};
-
-/// Handle to registry for userdata methods and metamethods.
-pub struct UserDataRegistry<'lua, T: 'static> {
-    // Fields
-    pub(crate) fields: Vec<(String, Callback<'lua, 'static>)>,
-    pub(crate) field_getters: Vec<(String, Callback<'lua, 'static>)>,
-    pub(crate) field_setters: Vec<(String, Callback<'lua, 'static>)>,
-    pub(crate) meta_fields: Vec<(String, Callback<'lua, 'static>)>,
-
-    // Methods
-    pub(crate) methods: Vec<(String, Callback<'lua, 'static>)>,
-    #[cfg(feature = "async")]
-    pub(crate) async_methods: Vec<(String, AsyncCallback<'lua, 'static>)>,
-    pub(crate) meta_methods: Vec<(String, Callback<'lua, 'static>)>,
-    #[cfg(feature = "async")]
-    pub(crate) async_meta_methods: Vec<(String, AsyncCallback<'lua, 'static>)>,
-
-    _type: PhantomData<T>,
-}
-
-impl<'lua, T: 'static> UserDataRegistry<'lua, T> {
-    pub(crate) const fn new() -> Self {
-        UserDataRegistry {
-            fields: Vec::new(),
-            field_getters: Vec::new(),
-            field_setters: Vec::new(),
-            meta_fields: Vec::new(),
-            methods: Vec::new(),
-            #[cfg(feature = "async")]
-            async_methods: Vec::new(),
-            meta_methods: Vec::new(),
-            #[cfg(feature = "async")]
-            async_meta_methods: Vec::new(),
-            _type: PhantomData,
-        }
-    }
-
-    fn box_method<M, A, R>(name: &str, method: M) -> Callback<'lua, 'static>
-    where
-        M: Fn(&'lua Lua, &T, A) -> Result<R> + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = get_function_name::<T>(name);
-        macro_rules! try_self_arg {
-            ($res:expr) => {
-                $res.map_err(|err| Error::bad_self_argument(&name, err))?
-            };
-            ($res:expr, $err:expr) => {
-                $res.map_err(|_| Error::bad_self_argument(&name, $err))?
-            };
-        }
-
-        Box::new(move |lua, nargs| unsafe {
-            if nargs == 0 {
-                let err = Error::from_lua_conversion("missing argument", "userdata", None);
-                try_self_arg!(Err(err));
-            }
-            let state = lua.state();
-            // Find absolute "self" index before processing args
-            let index = ffi::lua_absindex(state, -nargs);
-            // Self was at position 1, so we pass 2 here
-            let args = A::from_stack_args(nargs - 1, 2, Some(&name), lua);
-
-            match try_self_arg!(lua.get_userdata_type_id(index)) {
-                Some(id) if id == TypeId::of::<T>() => {
-                    let ud = try_self_arg!(get_userdata_ref::<T>(state, index));
-                    method(lua, &ud, args?)?.push_into_stack_multi(lua)
-                }
-                #[cfg(not(feature = "send"))]
-                Some(id) if id == TypeId::of::<Rc<T>>() => {
-                    let ud = try_self_arg!(get_userdata_ref::<Rc<T>>(state, index));
-                    method(lua, &ud, args?)?.push_into_stack_multi(lua)
-                }
-                #[cfg(not(feature = "send"))]
-                Some(id) if id == TypeId::of::<Rc<RefCell<T>>>() => {
-                    let ud = try_self_arg!(get_userdata_ref::<Rc<RefCell<T>>>(state, index));
-                    let ud = try_self_arg!(ud.try_borrow(), Error::UserDataBorrowError);
-                    method(lua, &ud, args?)?.push_into_stack_multi(lua)
-                }
-                Some(id) if id == TypeId::of::<Arc<T>>() => {
-                    let ud = try_self_arg!(get_userdata_ref::<Arc<T>>(state, index));
-                    method(lua, &ud, args?)?.push_into_stack_multi(lua)
-                }
-                Some(id) if id == TypeId::of::<Arc<Mutex<T>>>() => {
-                    let ud = try_self_arg!(get_userdata_ref::<Arc<Mutex<T>>>(state, index));
-                    let ud = try_self_arg!(ud.try_lock(), Error::UserDataBorrowError);
-                    method(lua, &ud, args?)?.push_into_stack_multi(lua)
-                }
-                #[cfg(feature = "parking_lot")]
-                Some(id) if id == TypeId::of::<Arc<parking_lot::Mutex<T>>>() => {
-                    let ud = get_userdata_ref::<Arc<parking_lot::Mutex<T>>>(state, index);
-                    let ud = try_self_arg!(ud);
-                    let ud = try_self_arg!(ud.try_lock().ok_or(Error::UserDataBorrowError));
-                    method(lua, &ud, args?)?.push_into_stack_multi(lua)
-                }
-                Some(id) if id == TypeId::of::<Arc<RwLock<T>>>() => {
-                    let ud = try_self_arg!(get_userdata_ref::<Arc<RwLock<T>>>(state, index));
-                    let ud = try_self_arg!(ud.try_read(), Error::UserDataBorrowError);
-                    method(lua, &ud, args?)?.push_into_stack_multi(lua)
-                }
-                #[cfg(feature = "parking_lot")]
-                Some(id) if id == TypeId::of::<Arc<parking_lot::RwLock<T>>>() => {
-                    let ud = get_userdata_ref::<Arc<parking_lot::RwLock<T>>>(state, index);
-                    let ud = try_self_arg!(ud);
-                    let ud = try_self_arg!(ud.try_read().ok_or(Error::UserDataBorrowError));
-                    method(lua, &ud, args?)?.push_into_stack_multi(lua)
-                }
-                _ => Err(Error::bad_self_argument(&name, Error::UserDataTypeMismatch)),
-            }
-        })
-    }
-
-    fn box_method_mut<M, A, R>(name: &str, method: M) -> Callback<'lua, 'static>
-    where
-        M: FnMut(&'lua Lua, &mut T, A) -> Result<R> + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = get_function_name::<T>(name);
-        macro_rules! try_self_arg {
-            ($res:expr) => {
-                $res.map_err(|err| Error::bad_self_argument(&name, err))?
-            };
-            ($res:expr, $err:expr) => {
-                $res.map_err(|_| Error::bad_self_argument(&name, $err))?
-            };
-        }
-
-        let method = RefCell::new(method);
-        Box::new(move |lua, nargs| unsafe {
-            let mut method = method
-                .try_borrow_mut()
-                .map_err(|_| Error::RecursiveMutCallback)?;
-            if nargs == 0 {
-                let err = Error::from_lua_conversion("missing argument", "userdata", None);
-                try_self_arg!(Err(err));
-            }
-            let state = lua.state();
-            // Find absolute "self" index before processing args
-            let index = ffi::lua_absindex(state, -nargs);
-            // Self was at position 1, so we pass 2 here
-            let args = A::from_stack_args(nargs - 1, 2, Some(&name), lua);
-
-            match try_self_arg!(lua.get_userdata_type_id(index)) {
-                Some(id) if id == TypeId::of::<T>() => {
-                    let mut ud = try_self_arg!(get_userdata_mut::<T>(state, index));
-                    method(lua, &mut ud, args?)?.push_into_stack_multi(lua)
-                }
-                #[cfg(not(feature = "send"))]
-                Some(id) if id == TypeId::of::<Rc<T>>() => Err(Error::UserDataBorrowMutError),
-                #[cfg(not(feature = "send"))]
-                Some(id) if id == TypeId::of::<Rc<RefCell<T>>>() => {
-                    let ud = try_self_arg!(get_userdata_mut::<Rc<RefCell<T>>>(state, index));
-                    let mut ud = try_self_arg!(ud.try_borrow_mut(), Error::UserDataBorrowMutError);
-                    method(lua, &mut ud, args?)?.push_into_stack_multi(lua)
-                }
-                Some(id) if id == TypeId::of::<Arc<T>>() => Err(Error::UserDataBorrowMutError),
-                Some(id) if id == TypeId::of::<Arc<Mutex<T>>>() => {
-                    let ud = try_self_arg!(get_userdata_mut::<Arc<Mutex<T>>>(state, index));
-                    let mut ud = try_self_arg!(ud.try_lock(), Error::UserDataBorrowMutError);
-                    method(lua, &mut ud, args?)?.push_into_stack_multi(lua)
-                }
-                #[cfg(feature = "parking_lot")]
-                Some(id) if id == TypeId::of::<Arc<parking_lot::Mutex<T>>>() => {
-                    let ud = get_userdata_mut::<Arc<parking_lot::Mutex<T>>>(state, index);
-                    let ud = try_self_arg!(ud);
-                    let mut ud = try_self_arg!(ud.try_lock().ok_or(Error::UserDataBorrowMutError));
-                    method(lua, &mut ud, args?)?.push_into_stack_multi(lua)
-                }
-                Some(id) if id == TypeId::of::<Arc<RwLock<T>>>() => {
-                    let ud = try_self_arg!(get_userdata_mut::<Arc<RwLock<T>>>(state, index));
-                    let mut ud = try_self_arg!(ud.try_write(), Error::UserDataBorrowMutError);
-                    method(lua, &mut ud, args?)?.push_into_stack_multi(lua)
-                }
-                #[cfg(feature = "parking_lot")]
-                Some(id) if id == TypeId::of::<Arc<parking_lot::RwLock<T>>>() => {
-                    let ud = get_userdata_mut::<Arc<parking_lot::RwLock<T>>>(state, index);
-                    let ud = try_self_arg!(ud);
-                    let mut ud = try_self_arg!(ud.try_write().ok_or(Error::UserDataBorrowMutError));
-                    method(lua, &mut ud, args?)?.push_into_stack_multi(lua)
-                }
-                _ => Err(Error::bad_self_argument(&name, Error::UserDataTypeMismatch)),
-            }
-        })
-    }
-
-    #[cfg(feature = "async")]
-    fn box_async_method<'s, M, A, MR, R>(name: &str, method: M) -> AsyncCallback<'lua, 'static>
-    where
-        'lua: 's,
-        T: 'static,
-        M: Fn(&'lua Lua, &'s T, A) -> MR + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        MR: Future<Output = Result<R>> + 's,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = Arc::new(get_function_name::<T>(name));
-        let method = Arc::new(method);
-
-        Box::new(move |lua, mut args| unsafe {
-            let name = name.clone();
-            let method = method.clone();
-            macro_rules! try_self_arg {
-                ($res:expr) => {
-                    $res.map_err(|err| Error::bad_self_argument(&name, err))?
-                };
-                ($res:expr, $err:expr) => {
-                    $res.map_err(|_| Error::bad_self_argument(&name, $err))?
-                };
-            }
-
-            Box::pin(async move {
-                let this = args.pop_front().ok_or_else(|| {
-                    Error::from_lua_conversion("missing argument", "userdata", None)
-                });
-                let this = try_self_arg!(AnyUserData::from_lua(try_self_arg!(this), lua));
-                let args = A::from_lua_args(args, 2, Some(&name), lua);
-
-                let (ref_thread, index) = (lua.ref_thread(), this.0.index);
-                match try_self_arg!(this.type_id()) {
-                    Some(id) if id == TypeId::of::<T>() => {
-                        let ud = try_self_arg!(get_userdata_ref::<T>(ref_thread, index));
-                        let ud = std::mem::transmute::<&T, &T>(&ud);
-                        method(lua, ud, args?).await?.push_into_stack_multi(lua)
-                    }
-                    #[cfg(not(feature = "send"))]
-                    Some(id) if id == TypeId::of::<Rc<T>>() => {
-                        let ud = try_self_arg!(get_userdata_ref::<Rc<T>>(ref_thread, index));
-                        let ud = std::mem::transmute::<&T, &T>(&ud);
-                        method(lua, ud, args?).await?.push_into_stack_multi(lua)
-                    }
-                    #[cfg(not(feature = "send"))]
-                    Some(id) if id == TypeId::of::<Rc<RefCell<T>>>() => {
-                        let ud =
-                            try_self_arg!(get_userdata_ref::<Rc<RefCell<T>>>(ref_thread, index));
-                        let ud = try_self_arg!(ud.try_borrow(), Error::UserDataBorrowError);
-                        let ud = std::mem::transmute::<&T, &T>(&ud);
-                        method(lua, ud, args?).await?.push_into_stack_multi(lua)
-                    }
-                    Some(id) if id == TypeId::of::<Arc<T>>() => {
-                        let ud = try_self_arg!(get_userdata_ref::<Arc<T>>(ref_thread, index));
-                        let ud = std::mem::transmute::<&T, &T>(&ud);
-                        method(lua, ud, args?).await?.push_into_stack_multi(lua)
-                    }
-                    Some(id) if id == TypeId::of::<Arc<Mutex<T>>>() => {
-                        let ud =
-                            try_self_arg!(get_userdata_ref::<Arc<Mutex<T>>>(ref_thread, index));
-                        let ud = try_self_arg!(ud.try_lock(), Error::UserDataBorrowError);
-                        let ud = std::mem::transmute::<&T, &T>(&ud);
-                        method(lua, ud, args?).await?.push_into_stack_multi(lua)
-                    }
-                    #[cfg(feature = "parking_lot")]
-                    Some(id) if id == TypeId::of::<Arc<parking_lot::Mutex<T>>>() => {
-                        let ud = get_userdata_ref::<Arc<parking_lot::Mutex<T>>>(ref_thread, index);
-                        let ud = try_self_arg!(ud);
-                        let ud = try_self_arg!(ud.try_lock().ok_or(Error::UserDataBorrowError));
-                        let ud = std::mem::transmute::<&T, &T>(&ud);
-                        method(lua, ud, args?).await?.push_into_stack_multi(lua)
-                    }
-                    Some(id) if id == TypeId::of::<Arc<RwLock<T>>>() => {
-                        let ud =
-                            try_self_arg!(get_userdata_ref::<Arc<RwLock<T>>>(ref_thread, index));
-                        let ud = try_self_arg!(ud.try_read(), Error::UserDataBorrowError);
-                        let ud = std::mem::transmute::<&T, &T>(&ud);
-                        method(lua, ud, args?).await?.push_into_stack_multi(lua)
-                    }
-                    #[cfg(feature = "parking_lot")]
-                    Some(id) if id == TypeId::of::<Arc<parking_lot::RwLock<T>>>() => {
-                        let ud = get_userdata_ref::<Arc<parking_lot::RwLock<T>>>(ref_thread, index);
-                        let ud = try_self_arg!(ud);
-                        let ud = try_self_arg!(ud.try_read().ok_or(Error::UserDataBorrowError));
-                        let ud = std::mem::transmute::<&T, &T>(&ud);
-                        method(lua, ud, args?).await?.push_into_stack_multi(lua)
-                    }
-                    _ => Err(Error::bad_self_argument(&name, Error::UserDataTypeMismatch)),
-                }
-            })
-        })
-    }
-
-    #[cfg(feature = "async")]
-    fn box_async_method_mut<'s, M, A, MR, R>(name: &str, method: M) -> AsyncCallback<'lua, 'static>
-    where
-        'lua: 's,
-        T: 'static,
-        M: Fn(&'lua Lua, &'s mut T, A) -> MR + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        MR: Future<Output = Result<R>> + 's,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = Arc::new(get_function_name::<T>(name));
-        let method = Arc::new(method);
-
-        Box::new(move |lua, mut args| unsafe {
-            let name = name.clone();
-            let method = method.clone();
-            macro_rules! try_self_arg {
-                ($res:expr) => {
-                    $res.map_err(|err| Error::bad_self_argument(&name, err))?
-                };
-                ($res:expr, $err:expr) => {
-                    $res.map_err(|_| Error::bad_self_argument(&name, $err))?
-                };
-            }
-
-            Box::pin(async move {
-                let this = args.pop_front().ok_or_else(|| {
-                    Error::from_lua_conversion("missing argument", "userdata", None)
-                });
-                let this = try_self_arg!(AnyUserData::from_lua(try_self_arg!(this), lua));
-                let args = A::from_lua_args(args, 2, Some(&name), lua);
-
-                let (ref_thread, index) = (lua.ref_thread(), this.0.index);
-                match try_self_arg!(this.type_id()) {
-                    Some(id) if id == TypeId::of::<T>() => {
-                        let mut ud = try_self_arg!(get_userdata_mut::<T>(ref_thread, index));
-                        let ud = std::mem::transmute::<&mut T, &mut T>(&mut ud);
-                        method(lua, ud, args?).await?.push_into_stack_multi(lua)
-                    }
-                    #[cfg(not(feature = "send"))]
-                    Some(id) if id == TypeId::of::<Rc<RefCell<T>>>() => {
-                        Err(Error::UserDataBorrowMutError)
-                    }
-                    #[cfg(not(feature = "send"))]
-                    Some(id) if id == TypeId::of::<Rc<RefCell<T>>>() => {
-                        let ud =
-                            try_self_arg!(get_userdata_mut::<Rc<RefCell<T>>>(ref_thread, index));
-                        let mut ud =
-                            try_self_arg!(ud.try_borrow_mut(), Error::UserDataBorrowMutError);
-                        let ud = std::mem::transmute::<&mut T, &mut T>(&mut ud);
-                        method(lua, ud, args?).await?.push_into_stack_multi(lua)
-                    }
-                    #[cfg(not(feature = "send"))]
-                    Some(id) if id == TypeId::of::<Arc<T>>() => Err(Error::UserDataBorrowMutError),
-                    Some(id) if id == TypeId::of::<Arc<Mutex<T>>>() => {
-                        let ud =
-                            try_self_arg!(get_userdata_mut::<Arc<Mutex<T>>>(ref_thread, index));
-                        let mut ud = try_self_arg!(ud.try_lock(), Error::UserDataBorrowMutError);
-                        let ud = std::mem::transmute::<&mut T, &mut T>(&mut ud);
-                        method(lua, ud, args?).await?.push_into_stack_multi(lua)
-                    }
-                    #[cfg(feature = "parking_lot")]
-                    Some(id) if id == TypeId::of::<Arc<parking_lot::Mutex<T>>>() => {
-                        let ud = get_userdata_mut::<Arc<parking_lot::Mutex<T>>>(ref_thread, index);
-                        let ud = try_self_arg!(ud);
-                        let mut ud =
-                            try_self_arg!(ud.try_lock().ok_or(Error::UserDataBorrowMutError));
-                        let ud = std::mem::transmute::<&mut T, &mut T>(&mut ud);
-                        method(lua, ud, args?).await?.push_into_stack_multi(lua)
-                    }
-                    Some(id) if id == TypeId::of::<Arc<RwLock<T>>>() => {
-                        let ud =
-                            try_self_arg!(get_userdata_mut::<Arc<RwLock<T>>>(ref_thread, index));
-                        let mut ud = try_self_arg!(ud.try_write(), Error::UserDataBorrowMutError);
-                        let ud = std::mem::transmute::<&mut T, &mut T>(&mut ud);
-                        method(lua, ud, args?).await?.push_into_stack_multi(lua)
-                    }
-                    #[cfg(feature = "parking_lot")]
-                    Some(id) if id == TypeId::of::<Arc<parking_lot::RwLock<T>>>() => {
-                        let ud = get_userdata_mut::<Arc<parking_lot::RwLock<T>>>(ref_thread, index);
-                        let ud = try_self_arg!(ud);
-                        let mut ud =
-                            try_self_arg!(ud.try_write().ok_or(Error::UserDataBorrowMutError));
-                        let ud = std::mem::transmute::<&mut T, &mut T>(&mut ud);
-                        method(lua, ud, args?).await?.push_into_stack_multi(lua)
-                    }
-                    _ => Err(Error::bad_self_argument(&name, Error::UserDataTypeMismatch)),
-                }
-            })
-        })
-    }
-
-    fn box_function<F, A, R>(name: &str, function: F) -> Callback<'lua, 'static>
-    where
-        F: Fn(&'lua Lua, A) -> Result<R> + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = get_function_name::<T>(name);
-        Box::new(move |lua, nargs| unsafe {
-            let args = A::from_stack_args(nargs, 1, Some(&name), lua)?;
-            function(lua, args)?.push_into_stack_multi(lua)
-        })
-    }
-
-    fn box_function_mut<F, A, R>(name: &str, function: F) -> Callback<'lua, 'static>
-    where
-        F: FnMut(&'lua Lua, A) -> Result<R> + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = get_function_name::<T>(name);
-        let function = RefCell::new(function);
-        Box::new(move |lua, nargs| unsafe {
-            let function = &mut *function
-                .try_borrow_mut()
-                .map_err(|_| Error::RecursiveMutCallback)?;
-            let args = A::from_stack_args(nargs, 1, Some(&name), lua)?;
-            function(lua, args)?.push_into_stack_multi(lua)
-        })
-    }
-
-    #[cfg(feature = "async")]
-    fn box_async_function<F, A, FR, R>(name: &str, function: F) -> AsyncCallback<'lua, 'static>
-    where
-        F: Fn(&'lua Lua, A) -> FR + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        FR: Future<Output = Result<R>> + 'lua,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = get_function_name::<T>(name);
-        Box::new(move |lua, args| unsafe {
-            let args = match A::from_lua_args(args, 1, Some(&name), lua) {
-                Ok(args) => args,
-                Err(e) => return Box::pin(future::err(e)),
-            };
-            let fut = function(lua, args);
-            Box::pin(async move { fut.await?.push_into_stack_multi(lua) })
-        })
-    }
-
-    pub(crate) fn check_meta_field<V>(lua: &'lua Lua, name: &str, value: V) -> Result<Value<'lua>>
-    where
-        V: IntoLua<'lua>,
-    {
-        let value = value.into_lua(lua)?;
-        if name == MetaMethod::Index || name == MetaMethod::NewIndex {
-            match value {
-                Value::Nil | Value::Table(_) | Value::Function(_) => {}
-                _ => {
-                    return Err(Error::MetaMethodTypeError {
-                        method: name.to_string(),
-                        type_name: value.type_name(),
-                        message: Some("expected nil, table or function".to_string()),
-                    })
-                }
-            }
-        }
-        value.into_lua(lua)
-    }
-}
-
-// Returns function name for the type `T`, without the module path
-fn get_function_name<T>(name: &str) -> StdString {
-    format!("{}.{name}", short_type_name::<T>())
-}
-
-impl<'lua, T: 'static> UserDataFields<'lua, T> for UserDataRegistry<'lua, T> {
-    fn add_field<V>(&mut self, name: impl AsRef<str>, value: V)
-    where
-        V: IntoLua<'lua> + Clone + 'static,
-    {
-        let name = name.as_ref().to_string();
-        self.fields.push((
-            name,
-            Box::new(move |lua, _| unsafe { value.clone().push_into_stack_multi(lua) }),
-        ));
-    }
-
-    fn add_field_method_get<M, R>(&mut self, name: impl AsRef<str>, method: M)
-    where
-        M: Fn(&'lua Lua, &T) -> Result<R> + MaybeSend + 'static,
-        R: IntoLua<'lua>,
-    {
-        let name = name.as_ref();
-        let method = Self::box_method(name, move |lua, data, ()| method(lua, data));
-        self.field_getters.push((name.into(), method));
-    }
-
-    fn add_field_method_set<M, A>(&mut self, name: impl AsRef<str>, method: M)
-    where
-        M: FnMut(&'lua Lua, &mut T, A) -> Result<()> + MaybeSend + 'static,
-        A: FromLua<'lua>,
-    {
-        let name = name.as_ref();
-        let method = Self::box_method_mut(name, method);
-        self.field_setters.push((name.into(), method));
-    }
-
-    fn add_field_function_get<F, R>(&mut self, name: impl AsRef<str>, function: F)
-    where
-        F: Fn(&'lua Lua, AnyUserData<'lua>) -> Result<R> + MaybeSend + 'static,
-        R: IntoLua<'lua>,
-    {
-        let name = name.as_ref();
-        let func = Self::box_function(name, function);
-        self.field_getters.push((name.into(), func));
-    }
-
-    fn add_field_function_set<F, A>(&mut self, name: impl AsRef<str>, mut function: F)
-    where
-        F: FnMut(&'lua Lua, AnyUserData<'lua>, A) -> Result<()> + MaybeSend + 'static,
-        A: FromLua<'lua>,
-    {
-        let name = name.as_ref();
-        let func = Self::box_function_mut(name, move |lua, (data, val)| function(lua, data, val));
-        self.field_setters.push((name.into(), func));
-    }
-
-    fn add_meta_field<V>(&mut self, name: impl AsRef<str>, value: V)
-    where
-        V: IntoLua<'lua> + Clone + 'static,
-    {
-        let name = name.as_ref().to_string();
-        let name2 = name.clone();
-        self.meta_fields.push((
-            name,
-            Box::new(move |lua, _| unsafe {
-                Self::check_meta_field(lua, &name2, value.clone())?.push_into_stack_multi(lua)
-            }),
-        ));
-    }
-
-    fn add_meta_field_with<F, R>(&mut self, name: impl AsRef<str>, f: F)
-    where
-        F: Fn(&'lua Lua) -> Result<R> + MaybeSend + 'static,
-        R: IntoLua<'lua>,
-    {
-        let name = name.as_ref().to_string();
-        let name2 = name.clone();
-        self.meta_fields.push((
-            name,
-            Box::new(move |lua, _| unsafe {
-                Self::check_meta_field(lua, &name2, f(lua)?)?.push_into_stack_multi(lua)
-            }),
-        ));
-    }
-
-    // Below are internal methods
-
-    fn append_fields_from<S>(&mut self, other: UserDataRegistry<'lua, S>) {
-        self.fields.extend(other.fields);
-        self.field_getters.extend(other.field_getters);
-        self.field_setters.extend(other.field_setters);
-        self.meta_fields.extend(other.meta_fields);
-    }
-}
-
-impl<'lua, T: 'static> UserDataMethods<'lua, T> for UserDataRegistry<'lua, T> {
-    fn add_method<M, A, R>(&mut self, name: impl AsRef<str>, method: M)
-    where
-        M: Fn(&'lua Lua, &T, A) -> Result<R> + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = name.as_ref();
-        self.methods
-            .push((name.into(), Self::box_method(name, method)));
-    }
-
-    fn add_method_mut<M, A, R>(&mut self, name: impl AsRef<str>, method: M)
-    where
-        M: FnMut(&'lua Lua, &mut T, A) -> Result<R> + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = name.as_ref();
-        self.methods
-            .push((name.into(), Self::box_method_mut(name, method)));
-    }
-
-    #[cfg(feature = "async")]
-    fn add_async_method<'s, M, A, MR, R>(&mut self, name: impl AsRef<str>, method: M)
-    where
-        'lua: 's,
-        T: 'static,
-        M: Fn(&'lua Lua, &'s T, A) -> MR + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        MR: Future<Output = Result<R>> + 's,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = name.as_ref();
-        self.async_methods
-            .push((name.into(), Self::box_async_method(name, method)));
-    }
-
-    #[cfg(feature = "async")]
-    fn add_async_method_mut<'s, M, A, MR, R>(&mut self, name: impl AsRef<str>, method: M)
-    where
-        'lua: 's,
-        T: 'static,
-        M: Fn(&'lua Lua, &'s mut T, A) -> MR + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        MR: Future<Output = Result<R>> + 's,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = name.as_ref();
-        self.async_methods
-            .push((name.into(), Self::box_async_method_mut(name, method)));
-    }
-
-    fn add_function<F, A, R>(&mut self, name: impl AsRef<str>, function: F)
-    where
-        F: Fn(&'lua Lua, A) -> Result<R> + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = name.as_ref();
-        self.methods
-            .push((name.into(), Self::box_function(name, function)));
-    }
-
-    fn add_function_mut<F, A, R>(&mut self, name: impl AsRef<str>, function: F)
-    where
-        F: FnMut(&'lua Lua, A) -> Result<R> + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = name.as_ref();
-        self.methods
-            .push((name.into(), Self::box_function_mut(name, function)));
-    }
-
-    #[cfg(feature = "async")]
-    fn add_async_function<F, A, FR, R>(&mut self, name: impl AsRef<str>, function: F)
-    where
-        F: Fn(&'lua Lua, A) -> FR + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        FR: Future<Output = Result<R>> + 'lua,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = name.as_ref();
-        self.async_methods
-            .push((name.into(), Self::box_async_function(name, function)));
-    }
-
-    fn add_meta_method<M, A, R>(&mut self, name: impl AsRef<str>, method: M)
-    where
-        M: Fn(&'lua Lua, &T, A) -> Result<R> + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = name.as_ref();
-        self.meta_methods
-            .push((name.into(), Self::box_method(name, method)));
-    }
-
-    fn add_meta_method_mut<M, A, R>(&mut self, name: impl AsRef<str>, method: M)
-    where
-        M: FnMut(&'lua Lua, &mut T, A) -> Result<R> + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = name.as_ref();
-        self.meta_methods
-            .push((name.into(), Self::box_method_mut(name, method)));
-    }
-
-    #[cfg(all(feature = "async", not(any(feature = "lua51", feature = "luau"))))]
-    fn add_async_meta_method<'s, M, A, MR, R>(&mut self, name: impl AsRef<str>, method: M)
-    where
-        'lua: 's,
-        T: 'static,
-        M: Fn(&'lua Lua, &'s T, A) -> MR + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        MR: Future<Output = Result<R>> + 's,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = name.as_ref();
-        self.async_meta_methods
-            .push((name.into(), Self::box_async_method(name, method)));
-    }
-
-    #[cfg(all(feature = "async", not(any(feature = "lua51", feature = "luau"))))]
-    fn add_async_meta_method_mut<'s, M, A, MR, R>(&mut self, name: impl AsRef<str>, method: M)
-    where
-        'lua: 's,
-        T: 'static,
-        M: Fn(&'lua Lua, &'s mut T, A) -> MR + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        MR: Future<Output = Result<R>> + 's,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = name.as_ref();
-        self.async_meta_methods
-            .push((name.into(), Self::box_async_method_mut(name, method)));
-    }
-
-    fn add_meta_function<F, A, R>(&mut self, name: impl AsRef<str>, function: F)
-    where
-        F: Fn(&'lua Lua, A) -> Result<R> + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = name.as_ref();
-        self.meta_methods
-            .push((name.into(), Self::box_function(name, function)));
-    }
-
-    fn add_meta_function_mut<F, A, R>(&mut self, name: impl AsRef<str>, function: F)
-    where
-        F: FnMut(&'lua Lua, A) -> Result<R> + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = name.as_ref();
-        self.meta_methods
-            .push((name.into(), Self::box_function_mut(name, function)));
-    }
-
-    #[cfg(all(feature = "async", not(any(feature = "lua51", feature = "luau"))))]
-    fn add_async_meta_function<F, A, FR, R>(&mut self, name: impl AsRef<str>, function: F)
-    where
-        F: Fn(&'lua Lua, A) -> FR + MaybeSend + 'static,
-        A: FromLuaMulti<'lua>,
-        FR: Future<Output = Result<R>> + 'lua,
-        R: IntoLuaMulti<'lua>,
-    {
-        let name = name.as_ref();
-        self.async_meta_methods
-            .push((name.into(), Self::box_async_function(name, function)));
-    }
-
-    // Below are internal methods used in generated code
-
-    fn append_methods_from<S>(&mut self, other: UserDataRegistry<'lua, S>) {
-        self.methods.extend(other.methods);
-        #[cfg(feature = "async")]
-        self.async_methods.extend(other.async_methods);
-        self.meta_methods.extend(other.meta_methods);
-        #[cfg(feature = "async")]
-        self.async_meta_methods.extend(other.async_meta_methods);
-    }
-}
-
-#[inline]
-unsafe fn get_userdata_ref<'a, T>(state: *mut ffi::lua_State, index: c_int) -> Result<Ref<'a, T>> {
-    (*get_userdata::<UserDataCell<T>>(state, index)).try_borrow()
-}
-
-#[inline]
-unsafe fn get_userdata_mut<'a, T>(
-    state: *mut ffi::lua_State,
-    index: c_int,
-) -> Result<RefMut<'a, T>> {
-    (*get_userdata::<UserDataCell<T>>(state, index)).try_borrow_mut()
-}
-
-macro_rules! lua_userdata_impl {
-    ($type:ty) => {
-        impl<T: UserData + 'static> UserData for $type {
-            fn add_fields<'lua, F: UserDataFields<'lua, Self>>(fields: &mut F) {
-                let mut orig_fields = UserDataRegistry::new();
-                T::add_fields(&mut orig_fields);
-                fields.append_fields_from(orig_fields);
-            }
-
-            fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
-                let mut orig_methods = UserDataRegistry::new();
-                T::add_methods(&mut orig_methods);
-                methods.append_methods_from(orig_methods);
-            }
-        }
-    };
-}
-
-#[cfg(not(feature = "send"))]
-lua_userdata_impl!(Rc<T>);
-#[cfg(not(feature = "send"))]
-lua_userdata_impl!(Rc<RefCell<T>>);
-
-lua_userdata_impl!(Arc<T>);
-lua_userdata_impl!(Arc<Mutex<T>>);
-lua_userdata_impl!(Arc<RwLock<T>>);
-#[cfg(feature = "parking_lot")]
-lua_userdata_impl!(Arc<parking_lot::Mutex<T>>);
-#[cfg(feature = "parking_lot")]
-lua_userdata_impl!(Arc<parking_lot::RwLock<T>>);
-
-// A special proxy object for UserData
-pub(crate) struct UserDataProxy<T>(pub(crate) PhantomData<T>);
-
-lua_userdata_impl!(UserDataProxy<T>);

src/util/error.rs

@@ -0,0 +1,432 @@
+use std::any::Any;
+use std::fmt::Write as _;
+use std::mem::MaybeUninit;
+use std::os::raw::{c_int, c_void};
+use std::panic::{catch_unwind, resume_unwind, AssertUnwindSafe};
+use std::ptr;
+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,
+};
+
+static WRAPPED_FAILURE_TYPE_KEY: u8 = 0;
+
+pub(crate) enum WrappedFailure {
+    None,
+    Error(Error),
+    Panic(Option<Box<dyn Any + Send + 'static>>),
+}
+
+impl TypeKey for WrappedFailure {
+    #[inline(always)]
+    fn type_key() -> *const c_void {
+        &WRAPPED_FAILURE_TYPE_KEY as *const u8 as *const c_void
+    }
+}
+
+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
+    }
+}
+
+// In the context of a lua callback, this will call the given function and if the given function
+// returns an error, *or if the given function panics*, this will result in a call to `lua_error` (a
+// longjmp). The error or panic is wrapped in such a way that when calling `pop_error` back on
+// the Rust side, it will resume the panic.
+//
+// This function assumes the structure of the stack at the beginning of a callback, that the only
+// elements on the stack are the arguments to the callback.
+//
+// This function uses some of the bottom of the stack for error handling, the given callback will be
+// given the number of arguments available as an argument, and should return the number of returns
+// as normal, but cannot assume that the arguments available start at 0.
+unsafe fn callback_error<F, R>(state: *mut ffi::lua_State, f: F) -> R
+where
+    F: FnOnce(c_int) -> Result<R>,
+{
+    let nargs = ffi::lua_gettop(state);
+
+    // We need 2 extra stack spaces to store preallocated memory and error/panic metatable
+    let extra_stack = if nargs < 2 { 2 - nargs } else { 1 };
+    ffi::luaL_checkstack(
+        state,
+        extra_stack,
+        cstr!("not enough stack space for callback error handling"),
+    );
+
+    // We cannot shadow Rust errors with Lua ones, we pre-allocate enough memory
+    // to store a wrapped error or panic *before* we proceed.
+    let ud = WrappedFailure::new_userdata(state);
+    ffi::lua_rotate(state, 1, 1);
+
+    match catch_unwind(AssertUnwindSafe(|| f(nargs))) {
+        Ok(Ok(r)) => {
+            ffi::lua_remove(state, 1);
+            r
+        }
+        Ok(Err(err)) => {
+            ffi::lua_settop(state, 1);
+
+            // Build `CallbackError` with traceback
+            let traceback = if ffi::lua_checkstack(state, ffi::LUA_TRACEBACK_STACK) != 0 {
+                ffi::luaL_traceback(state, state, ptr::null(), 0);
+                let traceback = to_string(state, -1);
+                ffi::lua_pop(state, 1);
+                traceback
+            } else {
+                "<not enough stack space for traceback>".to_string()
+            };
+            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)
+        }
+    }
+}
+
+// Pops an error off of the stack and returns it. The specific behavior depends on the type of the
+// error at the top of the stack:
+//   1) If the error is actually a panic, this will continue the panic.
+//   2) If the error on the top of the stack is actually an error, just returns it.
+//   3) Otherwise, interprets the error as the appropriate lua error.
+// Uses 2 stack spaces, does not call checkstack.
+pub(crate) unsafe fn pop_error(state: *mut ffi::lua_State, err_code: c_int) -> Error {
+    mlua_debug_assert!(
+        err_code != ffi::LUA_OK && err_code != ffi::LUA_YIELD,
+        "pop_error called with non-error return code"
+    );
+
+    match get_internal_userdata::<WrappedFailure>(state, -1, ptr::null()).as_mut() {
+        Some(WrappedFailure::Error(err)) => {
+            ffi::lua_pop(state, 1);
+            err.clone()
+        }
+        Some(WrappedFailure::Panic(panic)) => {
+            if let Some(p) = panic.take() {
+                resume_unwind(p);
+            } else {
+                Error::PreviouslyResumedPanic
+            }
+        }
+        _ => {
+            let err_string = to_string(state, -1);
+            ffi::lua_pop(state, 1);
+
+            match err_code {
+                ffi::LUA_ERRRUN => Error::RuntimeError(err_string),
+                ffi::LUA_ERRSYNTAX => {
+                    Error::SyntaxError {
+                        // This seems terrible, but as far as I can tell, this is exactly what the
+                        // stock Lua REPL does.
+                        incomplete_input: err_string.ends_with("<eof>") || err_string.ends_with("'<eof>'"),
+                        message: err_string,
+                    }
+                }
+                ffi::LUA_ERRERR => {
+                    // This error is raised when the error handler raises an error too many times
+                    // recursively, and continuing to trigger the error handler would cause a stack
+                    // overflow. It is not very useful to differentiate between this and "ordinary"
+                    // runtime errors, so we handle them the same way.
+                    Error::RuntimeError(err_string)
+                }
+                ffi::LUA_ERRMEM => Error::MemoryError(err_string),
+                #[cfg(any(feature = "lua53", feature = "lua52"))]
+                ffi::LUA_ERRGCMM => Error::GarbageCollectorError(err_string),
+                _ => mlua_panic!("unrecognized lua error code"),
+            }
+        }
+    }
+}
+
+// Call a function that calls into the Lua API and may trigger a Lua error (longjmp) in a safe way.
+// Wraps the inner function in a call to `lua_pcall`, so the inner function only has access to a
+// limited lua stack. `nargs` is the same as the the parameter to `lua_pcall`, and `nresults` is
+// always `LUA_MULTRET`. Provided function must *not* panic, and since it will generally be
+// longjmping, should not contain any values that implements Drop.
+// Internally uses 2 extra stack spaces, and does not call checkstack.
+pub(crate) unsafe fn protect_lua_call(
+    state: *mut ffi::lua_State,
+    nargs: c_int,
+    f: unsafe extern "C-unwind" fn(*mut ffi::lua_State) -> c_int,
+) -> Result<()> {
+    let stack_start = ffi::lua_gettop(state) - nargs;
+
+    MemoryState::relax_limit_with(state, || {
+        ffi::lua_pushcfunction(state, error_traceback);
+        ffi::lua_pushcfunction(state, f);
+    });
+    if nargs > 0 {
+        ffi::lua_rotate(state, stack_start + 1, 2);
+    }
+
+    let ret = ffi::lua_pcall(state, nargs, ffi::LUA_MULTRET, stack_start + 1);
+    ffi::lua_remove(state, stack_start + 1);
+
+    if ret == ffi::LUA_OK {
+        Ok(())
+    } else {
+        Err(pop_error(state, ret))
+    }
+}
+
+// Call a function that calls into the Lua API and may trigger a Lua error (longjmp) in a safe way.
+// Wraps the inner function in a call to `lua_pcall`, so the inner function only has access to a
+// limited lua stack. `nargs` and `nresults` are similar to the parameters of `lua_pcall`, but the
+// given function return type is not the return value count, instead the inner function return
+// values are assumed to match the `nresults` param. Provided function must *not* panic, and since
+// it will generally be longjmping, should not contain any values that implements Drop.
+// Internally uses 3 extra stack spaces, and does not call checkstack.
+pub(crate) unsafe fn protect_lua_closure<F, R>(
+    state: *mut ffi::lua_State,
+    nargs: c_int,
+    nresults: c_int,
+    f: F,
+) -> Result<R>
+where
+    F: Fn(*mut ffi::lua_State) -> R,
+    R: Copy,
+{
+    struct Params<F, R: Copy> {
+        function: 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,
+        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));
+
+        if (*params).nresults == ffi::LUA_MULTRET {
+            ffi::lua_gettop(state)
+        } else {
+            (*params).nresults
+        }
+    }
+
+    let stack_start = ffi::lua_gettop(state) - nargs;
+
+    MemoryState::relax_limit_with(state, || {
+        ffi::lua_pushcfunction(state, error_traceback);
+        ffi::lua_pushcfunction(state, do_call::<F, R>);
+    });
+    if nargs > 0 {
+        ffi::lua_rotate(state, stack_start + 1, 2);
+    }
+
+    let mut params = Params {
+        function: f,
+        result: MaybeUninit::uninit(),
+        nresults,
+    };
+
+    ffi::lua_pushlightuserdata(state, &mut params as *mut Params<F, R> as *mut c_void);
+    let ret = ffi::lua_pcall(state, nargs + 1, nresults, stack_start + 1);
+    ffi::lua_remove(state, stack_start + 1);
+
+    if ret == ffi::LUA_OK {
+        // `LUA_OK` is only returned when the `do_call` function has completed successfully, so
+        // `params.result` is definitely initialized.
+        Ok(params.result.assume_init())
+    } else {
+        Err(pop_error(state, ret))
+    }
+}
+
+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
+    #[cfg(feature = "luau")]
+    if MemoryState::limit_reached(state) {
+        return 0;
+    }
+
+    if ffi::lua_checkstack(state, 2) == 0 {
+        // If we don't have enough stack space to even check the error type, do
+        // nothing so we don't risk shadowing a rust panic.
+        return 1;
+    }
+
+    if get_internal_userdata::<WrappedFailure>(state, -1, ptr::null()).is_null() {
+        let s = ffi::luaL_tolstring(state, -1, ptr::null_mut());
+        if ffi::lua_checkstack(state, ffi::LUA_TRACEBACK_STACK) != 0 {
+            ffi::luaL_traceback(state, state, s, 0);
+            ffi::lua_remove(state, -2);
+        }
+    }
+
+    1
+}
+
+// A variant of `error_traceback` that can safely inspect another (yielded) thread stack
+pub(crate) unsafe fn error_traceback_thread(state: *mut ffi::lua_State, thread: *mut ffi::lua_State) {
+    // Move error object to the main thread to safely call `__tostring` metamethod if present
+    ffi::lua_xmove(thread, state, 1);
+
+    if get_internal_userdata::<WrappedFailure>(state, -1, ptr::null()).is_null() {
+        let s = ffi::luaL_tolstring(state, -1, ptr::null_mut());
+        if ffi::lua_checkstack(state, ffi::LUA_TRACEBACK_STACK) != 0 {
+            ffi::luaL_traceback(state, thread, s, 0);
+            ffi::lua_remove(state, -2);
+        }
+    }
+}
+
+// Initialize the error, panic, and destructed userdata metatables.
+pub(crate) unsafe fn init_error_registry(state: *mut ffi::lua_State) -> Result<()> {
+    check_stack(state, 7)?;
+
+    // Create error and panic metatables
+
+    static ERROR_PRINT_BUFFER_KEY: u8 = 0;
+
+    unsafe extern "C-unwind" fn error_tostring(state: *mut ffi::lua_State) -> c_int {
+        callback_error(state, |_| {
+            check_stack(state, 3)?;
+
+            let err_buf = match get_internal_userdata::<WrappedFailure>(state, -1, ptr::null()).as_ref() {
+                Some(WrappedFailure::Error(error)) => {
+                    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;
+                    ffi::lua_pop(state, 2);
+
+                    (*err_buf).clear();
+                    // Depending on how the API is used and what error types scripts are given, it may
+                    // be possible to make this consume arbitrary amounts of memory (for example, some
+                    // kind of recursive error structure?)
+                    let _ = write!(&mut (*err_buf), "{error}");
+                    Ok(err_buf)
+                }
+                Some(WrappedFailure::Panic(Some(ref 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;
+                    (*err_buf).clear();
+                    ffi::lua_pop(state, 2);
+
+                    if let Some(msg) = panic.downcast_ref::<&str>() {
+                        let _ = write!(&mut (*err_buf), "{msg}");
+                    } else if let Some(msg) = panic.downcast_ref::<String>() {
+                        let _ = write!(&mut (*err_buf), "{msg}");
+                    } else {
+                        let _ = write!(&mut (*err_buf), "<panic>");
+                    };
+                    Ok(err_buf)
+                }
+                Some(WrappedFailure::Panic(None)) => Err(Error::PreviouslyResumedPanic),
+                _ => {
+                    // I'm not sure whether this is possible to trigger without bugs in mlua?
+                    Err(Error::UserDataTypeMismatch)
+                }
+            }?;
+
+            push_string(state, (*err_buf).as_bytes(), true)?;
+            (*err_buf).clear();
+
+            Ok(1)
+        })
+    }
+
+    init_internal_metatable::<WrappedFailure>(
+        state,
+        Some(|state| {
+            ffi::lua_pushcfunction(state, error_tostring);
+            rawset_field(state, -2, "__tostring")
+        }),
+    )?;
+
+    // Create destructed userdata metatable
+
+    unsafe extern "C-unwind" fn destructed_error(state: *mut ffi::lua_State) -> c_int {
+        callback_error(state, |_| Err(Error::CallbackDestructed))
+    }
+
+    push_table(state, 0, 26, true)?;
+    ffi::lua_pushcfunction(state, destructed_error);
+    for &method in &[
+        "__add",
+        "__sub",
+        "__mul",
+        "__div",
+        "__mod",
+        "__pow",
+        "__unm",
+        #[cfg(any(feature = "lua54", feature = "lua53", feature = "luau"))]
+        "__idiv",
+        #[cfg(any(feature = "lua54", feature = "lua53"))]
+        "__band",
+        #[cfg(any(feature = "lua54", feature = "lua53"))]
+        "__bor",
+        #[cfg(any(feature = "lua54", feature = "lua53"))]
+        "__bxor",
+        #[cfg(any(feature = "lua54", feature = "lua53"))]
+        "__bnot",
+        #[cfg(any(feature = "lua54", feature = "lua53"))]
+        "__shl",
+        #[cfg(any(feature = "lua54", feature = "lua53"))]
+        "__shr",
+        "__concat",
+        "__len",
+        "__eq",
+        "__lt",
+        "__le",
+        "__index",
+        "__newindex",
+        "__call",
+        "__tostring",
+        #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52", feature = "luajit52"))]
+        "__pairs",
+        #[cfg(any(feature = "lua53", feature = "lua52", feature = "luajit52"))]
+        "__ipairs",
+        #[cfg(feature = "luau")]
+        "__iter",
+        #[cfg(feature = "lua54")]
+        "__close",
+    ] {
+        ffi::lua_pushvalue(state, -1);
+        rawset_field(state, -3, method)?;
+    }
+    ffi::lua_pop(state, 1);
+
+    protect_lua!(state, 1, 0, fn(state) {
+        let destructed_mt_key = &DESTRUCTED_USERDATA_METATABLE as *const u8 as *const c_void;
+        ffi::lua_rawsetp(state, ffi::LUA_REGISTRYINDEX, destructed_mt_key);
+    })?;
+
+    // Create error print buffer
+    init_internal_metatable::<String>(state, None)?;
+    push_internal_userdata(state, String::new(), true)?;
+    protect_lua!(state, 1, 0, fn(state) {
+        let err_buf_key = &ERROR_PRINT_BUFFER_KEY as *const u8 as *const c_void;
+        ffi::lua_rawsetp(state, ffi::LUA_REGISTRYINDEX, err_buf_key);
+    })?;
+
+    Ok(())
+}

src/util/short_names.rs

@@ -25,22 +25,17 @@ pub(crate) fn short_type_name<T: ?Sized>() -> String {
 
         // Collapse everything up to the next special character,
         // then skip over it
-        if let Some(special_character_index) = rest_of_string
-            .find(|c: char| [' ', '<', '>', '(', ')', '[', ']', ',', ';'].contains(&c))
+        if let Some(special_character_index) =
+            rest_of_string.find(|c: char| [' ', '<', '>', '(', ')', '[', ']', ',', ';'].contains(&c))
         {
-            let segment_to_collapse = rest_of_string
-                .get(0..special_character_index)
-                .unwrap_or_default();
+            let segment_to_collapse = rest_of_string.get(0..special_character_index).unwrap_or_default();
             parsed_name += collapse_type_name(segment_to_collapse);
             // Insert the special character
-            let special_character =
-                &rest_of_string[special_character_index..=special_character_index];
+            let special_character = &rest_of_string[special_character_index..=special_character_index];
             parsed_name.push_str(special_character);
 
             match special_character {
-                ">" | ")" | "]"
-                    if rest_of_string[special_character_index + 1..].starts_with("::") =>
-                {
+                ">" | ")" | "]" if rest_of_string[special_character_index + 1..].starts_with("::") => {
                     parsed_name.push_str("::");
                     // Move the index past the "::"
                     index += special_character_index + 3;
@@ -77,9 +72,6 @@ mod tests {
             short_type_name::<HashMap<String, Option<[i32; 3]>>>(),
             "HashMap<String, Option<[i32; 3]>>"
         );
-        assert_eq!(
-            short_type_name::<dyn Fn(i32) -> i32>(),
-            "dyn Fn(i32) -> i32"
-        );
+        assert_eq!(short_type_name::<dyn Fn(i32) -> i32>(), "dyn Fn(i32) -> i32");
     }
 }

src/util/types.rs

@@ -0,0 +1,82 @@
+use std::any::Any;
+use std::os::raw::c_void;
+
+use crate::types::{Callback, CallbackUpvalue};
+
+#[cfg(feature = "async")]
+use crate::types::{AsyncCallback, AsyncCallbackUpvalue, AsyncPollUpvalue};
+
+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 {
+        &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 {
+        &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 {
+        &CALLBACK_UPVALUE_TYPE_KEY as *const u8 as *const c_void
+    }
+}
+
+#[cfg(feature = "async")]
+static ASYNC_CALLBACK_TYPE_KEY: u8 = 0;
+
+#[cfg(feature = "async")]
+impl TypeKey for AsyncCallback {
+    #[inline(always)]
+    fn type_key() -> *const c_void {
+        &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 {
+        &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 {
+        &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 {
+        &WAKER_TYPE_KEY as *const u8 as *const c_void
+    }
+}

src/util/userdata.rs

@@ -0,0 +1,380 @@
+use std::ffi::CStr;
+use std::os::raw::{c_int, c_void};
+use std::{ptr, str};
+
+use crate::error::Result;
+use crate::util::{check_stack, push_string, push_table, rawset_field, TypeKey};
+
+// Pushes the userdata and attaches a metatable with __gc method.
+// Internally uses 3 stack spaces, does not call checkstack.
+pub(crate) unsafe fn push_internal_userdata<T: TypeKey>(
+    state: *mut ffi::lua_State,
+    t: T,
+    protect: bool,
+) -> Result<()> {
+    push_userdata(state, t, protect)?;
+    get_internal_metatable::<T>(state);
+    ffi::lua_setmetatable(state, -2);
+    Ok(())
+}
+
+#[track_caller]
+pub(crate) unsafe fn get_internal_metatable<T: TypeKey>(state: *mut ffi::lua_State) {
+    ffi::lua_rawgetp(state, ffi::LUA_REGISTRYINDEX, T::type_key());
+    debug_assert!(ffi::lua_isnil(state, -1) == 0, "internal metatable not found");
+}
+
+// Initialize the internal metatable for a type T (with __gc method).
+// 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<()>>,
+) -> Result<()> {
+    check_stack(state, 6)?;
+
+    push_table(state, 0, 3, true)?;
+
+    #[cfg(not(feature = "luau"))]
+    {
+        ffi::lua_pushcfunction(state, userdata_destructor::<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| {
+        ffi::lua_rawsetp(state, ffi::LUA_REGISTRYINDEX, T::type_key());
+    })?;
+
+    Ok(())
+}
+
+// Uses 2 stack spaces, 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 T {
+    let ud = ffi::lua_touserdata(state, index) as *mut T;
+    if ud.is_null() || ffi::lua_getmetatable(state, index) == 0 {
+        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 {
+        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();
+        }
+    }
+    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 {
+        protect_lua!(state, 0, 1, |state| {
+            ffi::lua_newuserdata(state, std::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(())
+}
+
+// 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 {
+        protect_lua!(state, 0, 1, |state| {
+            ffi::lua_newuserdatauv(state, std::mem::size_of::<T>(), nuvalue) as *mut T
+        })?
+    } else {
+        ffi::lua_newuserdatauv(state, std::mem::size_of::<T>(), nuvalue) as *mut T
+    };
+    ptr::write(ud, t);
+    Ok(())
+}
+
+#[inline]
+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.
+    get_destructed_userdata_metatable(state);
+    ffi::lua_setmetatable(state, -2);
+    let ud = get_userdata::<T>(state, -1);
+
+    // Update userdata tag to disable destructor and mark as destructed
+    #[cfg(feature = "luau")]
+    ffi::lua_setuserdatatag(state, -1, 1);
+
+    ffi::lua_pop(state, 1);
+    ptr::read(ud)
+}
+
+pub(crate) unsafe fn get_destructed_userdata_metatable(state: *mut ffi::lua_State) {
+    let key = &DESTRUCTED_USERDATA_METATABLE as *const u8 as *const c_void;
+    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

@@ -1,38 +1,37 @@
-use std::borrow::Cow;
+use std::cell::RefCell;
 use std::cmp::Ordering;
-use std::collections::HashSet;
-use std::iter::{self, FromIterator};
-use std::ops::Index;
+use std::collections::{vec_deque, HashSet, VecDeque};
+use std::ops::{Deref, DerefMut};
 use std::os::raw::{c_int, c_void};
 use std::string::String as StdString;
 use std::sync::Arc;
-use std::{fmt, mem, ptr, slice, str, vec};
+use std::{fmt, mem, ptr, str};
 
 use num_traits::FromPrimitive;
 
-#[cfg(feature = "serialize")]
-use {
-    crate::table::SerializableTable,
-    rustc_hash::FxHashSet,
-    serde::ser::{self, Serialize, Serializer},
-    std::{cell::RefCell, convert::TryInto, rc::Rc, result::Result as StdResult},
-};
-
 use crate::error::{Error, Result};
 use crate::function::Function;
-use crate::lua::Lua;
-use crate::string::String;
+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::userdata::AnyUserData;
 use crate::util::{check_stack, StackGuard};
 
+#[cfg(feature = "serialize")]
+use {
+    crate::table::SerializableTable,
+    rustc_hash::FxHashSet,
+    serde::ser::{self, Serialize, Serializer},
+    std::{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.
 #[derive(Clone)]
-pub enum Value<'lua> {
+pub enum Value {
     /// The Lua value `nil`.
     Nil,
     /// The Lua value `true` or `false`.
@@ -52,27 +51,27 @@ pub enum Value<'lua> {
     /// An interned string, managed by Lua.
     ///
     /// Unlike Rust strings, Lua strings may not be valid UTF-8.
-    String(String<'lua>),
+    String(String),
     /// Reference to a Lua table.
-    Table(Table<'lua>),
+    Table(Table),
     /// Reference to a Lua function (or closure).
-    Function(Function<'lua>),
+    Function(Function),
     /// Reference to a Lua thread (or coroutine).
-    Thread(Thread<'lua>),
+    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<'lua>),
+    UserData(AnyUserData),
     /// `Error` is a special builtin userdata type. When received from Lua it is implicitly cloned.
-    Error(Error),
+    Error(Box<Error>),
 }
 
 pub use self::Value::Nil;
 
-impl<'lua> Value<'lua> {
+impl Value {
     /// A special value (lightuserdata) to represent null value.
     ///
     /// It can be used in Lua tables without downsides of `nil`.
-    pub const NULL: Value<'static> = Value::LightUserData(LightUserData(ptr::null_mut()));
+    pub const NULL: Value = Value::LightUserData(LightUserData(ptr::null_mut()));
 
     /// Returns type name of this value.
     pub const fn type_name(&self) -> &'static str {
@@ -117,8 +116,8 @@ impl<'lua> Value<'lua> {
 
     /// Converts the value to a generic C pointer.
     ///
-    /// The value can be a userdata, a table, a thread, a string, or a function; otherwise it returns NULL.
-    /// Different objects will give different pointers.
+    /// The value can be a userdata, a table, a thread, a string, or a function; otherwise it
+    /// returns NULL. Different objects will give different pointers.
     /// There is no way to convert the pointer back to its original value.
     ///
     /// Typically this function is used only for hashing and debug information.
@@ -137,7 +136,8 @@ impl<'lua> Value<'lua> {
 
     /// 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.
+    /// If the value has a metatable with a `__tostring` method, then it will be called to get the
+    /// result.
     pub fn to_string(&self) -> Result<StdString> {
         match self {
             Value::Nil => Ok("nil".to_string()),
@@ -153,15 +153,16 @@ impl<'lua> Value<'lua> {
             | Value::Function(Function(r))
             | Value::Thread(Thread(r, ..))
             | Value::UserData(AnyUserData(r, ..)) => unsafe {
-                let state = r.lua.state();
+                let lua = r.lua.lock();
+                let state = lua.state();
                 let _guard = StackGuard::new(state);
                 check_stack(state, 3)?;
 
-                r.lua.push_ref(r);
+                lua.push_ref(r);
                 protect_lua!(state, 1, 1, fn(state) {
                     ffi::luaL_tolstring(state, -1, ptr::null_mut());
                 })?;
-                Ok(String(r.lua.pop_ref()).to_str()?.to_string())
+                Ok(String(lua.pop_ref()).to_str()?.to_string())
             },
             Value::Error(err) => Ok(err.to_string()),
         }
@@ -252,8 +253,7 @@ impl<'lua> Value<'lua> {
     /// 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> {
-        #[allow(clippy::useless_conversion)]
-        self.as_integer().and_then(|i| i64::try_from(i).ok())
+        self.as_integer().map(i64::from)
     }
 
     /// Cast the value to `u64`.
@@ -330,19 +330,20 @@ impl<'lua> Value<'lua> {
         }
     }
 
-    /// Cast the value to [`str`].
+    /// Cast the value to [`BorrowedStr`].
     ///
-    /// If the value is a Lua [`String`], try to convert it to [`str`] or return `None` otherwise.
+    /// If the value is a Lua [`String`], try to convert it to [`BorrowedStr`] or return `None`
+    /// otherwise.
     #[inline]
-    pub fn as_str(&self) -> Option<&str> {
+    pub fn as_str(&self) -> Option<BorrowedStr> {
         self.as_string().and_then(|s| s.to_str().ok())
     }
 
-    /// Cast the value to [`Cow<str>`].
+    /// Cast the value to [`StdString`].
     ///
-    /// If the value is a Lua [`String`], converts it to [`Cow<str>`] or returns `None` otherwise.
+    /// If the value is a Lua [`String`], converts it to [`StdString`] or returns `None` otherwise.
     #[inline]
-    pub fn as_string_lossy(&self) -> Option<Cow<str>> {
+    pub fn as_string_lossy(&self) -> Option<StdString> {
         self.as_string().map(|s| s.to_string_lossy())
     }
 
@@ -442,7 +443,7 @@ impl<'lua> Value<'lua> {
     #[cfg(feature = "serialize")]
     #[cfg_attr(docsrs, doc(cfg(feature = "serialize")))]
     #[doc(hidden)]
-    pub fn to_serializable(&self) -> SerializableValue<'_, 'lua> {
+    pub fn to_serializable(&self) -> SerializableValue {
         SerializableValue::new(self, Default::default(), None)
     }
 
@@ -478,7 +479,7 @@ impl<'lua> Value<'lua> {
             (Value::Integer(_) | Value::Number(_), _) => Ordering::Less,
             (_, Value::Integer(_) | Value::Number(_)) => Ordering::Greater,
             // String
-            (Value::String(a), Value::String(b)) => a.as_bytes().cmp(b.as_bytes()),
+            (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
@@ -524,7 +525,7 @@ impl<'lua> Value<'lua> {
     }
 }
 
-impl fmt::Debug for Value<'_> {
+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());
@@ -547,7 +548,7 @@ impl fmt::Debug for Value<'_> {
     }
 }
 
-impl<'lua> PartialEq for Value<'lua> {
+impl PartialEq for Value {
     fn eq(&self, other: &Self) -> bool {
         match (self, other) {
             (Value::Nil, Value::Nil) => true,
@@ -569,7 +570,7 @@ impl<'lua> PartialEq for Value<'lua> {
     }
 }
 
-impl<'lua> AsRef<Value<'lua>> for Value<'lua> {
+impl AsRef<Value> for Value {
     #[inline]
     fn as_ref(&self) -> &Self {
         self
@@ -579,15 +580,15 @@ impl<'lua> AsRef<Value<'lua>> for Value<'lua> {
 /// A wrapped [`Value`] with customized serialization behavior.
 #[cfg(feature = "serialize")]
 #[cfg_attr(docsrs, doc(cfg(feature = "serialize")))]
-pub struct SerializableValue<'a, 'lua> {
-    value: &'a Value<'lua>,
+pub struct SerializableValue<'a> {
+    value: &'a Value,
     options: crate::serde::de::Options,
     // In many cases we don't need `visited` map, so don't allocate memory by default
     visited: Option<Rc<RefCell<FxHashSet<*const c_void>>>>,
 }
 
 #[cfg(feature = "serialize")]
-impl<'lua> Serialize for Value<'lua> {
+impl Serialize for Value {
     #[inline]
     fn serialize<S: Serializer>(&self, serializer: S) -> StdResult<S::Ok, S::Error> {
         SerializableValue::new(self, Default::default(), None).serialize(serializer)
@@ -595,10 +596,10 @@ impl<'lua> Serialize for Value<'lua> {
 }
 
 #[cfg(feature = "serialize")]
-impl<'a, 'lua> SerializableValue<'a, 'lua> {
+impl<'a> SerializableValue<'a> {
     #[inline]
     pub(crate) fn new(
-        value: &'a Value<'lua>,
+        value: &'a Value,
         options: crate::serde::de::Options,
         visited: Option<&Rc<RefCell<FxHashSet<*const c_void>>>>,
     ) -> Self {
@@ -650,7 +651,7 @@ impl<'a, 'lua> SerializableValue<'a, 'lua> {
 }
 
 #[cfg(feature = "serialize")]
-impl<'a, 'lua> Serialize for SerializableValue<'a, 'lua> {
+impl<'a> Serialize for SerializableValue<'a> {
     fn serialize<S>(&self, serializer: S) -> StdResult<S::Ok, S::Error>
     where
         S: Serializer,
@@ -659,8 +660,7 @@ impl<'a, 'lua> Serialize for SerializableValue<'a, 'lua> {
             Value::Nil => serializer.serialize_unit(),
             Value::Boolean(b) => serializer.serialize_bool(*b),
             #[allow(clippy::useless_conversion)]
-            Value::Integer(i) => serializer
-                .serialize_i64((*i).try_into().expect("cannot convert Lua Integer to i64")),
+            Value::Integer(i) => serializer.serialize_i64((*i).into()),
             Value::Number(n) => serializer.serialize_f64(*n),
             #[cfg(feature = "luau")]
             Value::Vector(v) => v.serialize(serializer),
@@ -690,9 +690,9 @@ impl<'a, 'lua> Serialize for SerializableValue<'a, 'lua> {
 }
 
 /// Trait for types convertible to `Value`.
-pub trait IntoLua<'lua>: Sized {
+pub trait IntoLua: Sized {
     /// Performs the conversion.
-    fn into_lua(self, lua: &'lua Lua) -> Result<Value<'lua>>;
+    fn into_lua(self, lua: &Lua) -> Result<Value>;
 
     /// Pushes the value into the Lua stack.
     ///
@@ -700,15 +700,15 @@ pub trait IntoLua<'lua>: Sized {
     /// This method does not check Lua stack space.
     #[doc(hidden)]
     #[inline]
-    unsafe fn push_into_stack(self, lua: &'lua Lua) -> Result<()> {
-        lua.push_value(self.into_lua(lua)?)
+    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<'lua>: Sized {
+pub trait FromLua: Sized {
     /// Performs the conversion.
-    fn from_lua(value: Value<'lua>, lua: &'lua Lua) -> Result<Self>;
+    fn from_lua(value: Value, lua: &Lua) -> Result<Self>;
 
     /// Performs the conversion for an argument (eg. function argument).
     ///
@@ -716,7 +716,7 @@ pub trait FromLua<'lua>: Sized {
     /// `to` is a function name that received the argument.
     #[doc(hidden)]
     #[inline]
-    fn from_lua_arg(arg: Value<'lua>, i: usize, to: Option<&str>, lua: &'lua Lua) -> Result<Self> {
+    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,
@@ -728,19 +728,14 @@ pub trait FromLua<'lua>: Sized {
     /// Performs the conversion for a value in the Lua stack at index `idx`.
     #[doc(hidden)]
     #[inline]
-    unsafe fn from_stack(idx: c_int, lua: &'lua Lua) -> Result<Self> {
-        Self::from_lua(lua.stack_value(idx), lua)
+    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: &'lua Lua,
-    ) -> Result<Self> {
+    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,
@@ -751,192 +746,99 @@ pub trait FromLua<'lua>: Sized {
 }
 
 /// Multiple Lua values used for both argument passing and also for multiple return values.
-#[derive(Debug, Clone)]
-pub struct MultiValue<'lua> {
-    vec: Vec<Value<'lua>>,
-    lua: Option<&'lua Lua>,
-}
+#[derive(Default, Debug, Clone)]
+pub struct MultiValue(VecDeque<Value>);
 
-impl Drop for MultiValue<'_> {
-    fn drop(&mut self) {
-        if let Some(lua) = self.lua {
-            let vec = mem::take(&mut self.vec);
-            lua.push_multivalue_to_pool(vec);
-        }
+impl Deref for MultiValue {
+    type Target = VecDeque<Value>;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &self.0
     }
 }
 
-impl<'lua> MultiValue<'lua> {
+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.
-    pub const fn new() -> MultiValue<'lua> {
-        MultiValue {
-            vec: Vec::new(),
-            lua: None,
-        }
-    }
-
-    /// Similar to `new` but can reuse previously used container with allocated capacity.
-    #[inline]
-    pub(crate) fn with_lua_and_capacity(lua: &'lua Lua, capacity: usize) -> MultiValue<'lua> {
-        let vec = lua
-            .pop_multivalue_from_pool()
-            .map(|mut vec| {
-                vec.reserve(capacity);
-                vec
-            })
-            .unwrap_or_else(|| Vec::with_capacity(capacity));
-        MultiValue {
-            vec,
-            lua: Some(lua),
+    #[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<'lua> Default for MultiValue<'lua> {
+impl FromIterator<Value> for MultiValue {
     #[inline]
-    fn default() -> MultiValue<'lua> {
-        MultiValue::new()
+    fn from_iter<I: IntoIterator<Item = Value>>(iter: I) -> Self {
+        let mut multi_value = MultiValue::new();
+        multi_value.extend(iter);
+        multi_value
     }
 }
 
-impl<'lua> FromIterator<Value<'lua>> for MultiValue<'lua> {
-    #[inline]
-    fn from_iter<I: IntoIterator<Item = Value<'lua>>>(iter: I) -> Self {
-        MultiValue::from_vec(Vec::from_iter(iter))
-    }
-}
-
-impl<'lua> IntoIterator for MultiValue<'lua> {
-    type Item = Value<'lua>;
-    type IntoIter = iter::Rev<vec::IntoIter<Value<'lua>>>;
+impl IntoIterator for MultiValue {
+    type Item = Value;
+    type IntoIter = vec_deque::IntoIter<Value>;
 
     #[inline]
     fn into_iter(mut self) -> Self::IntoIter {
-        let vec = mem::take(&mut self.vec);
+        let deque = mem::take(&mut self.0);
         mem::forget(self);
-        vec.into_iter().rev()
+        deque.into_iter()
     }
 }
 
-impl<'a, 'lua> IntoIterator for &'a MultiValue<'lua> {
-    type Item = &'a Value<'lua>;
-    type IntoIter = iter::Rev<slice::Iter<'a, Value<'lua>>>;
+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.vec.iter().rev()
-    }
-}
-
-impl<'lua> Index<usize> for MultiValue<'lua> {
-    type Output = Value<'lua>;
-
-    #[inline]
-    fn index(&self, index: usize) -> &Self::Output {
-        if let Some(result) = self.get(index) {
-            result
-        } else {
-            panic!(
-                "index out of bounds: the len is {} but the index is {}",
-                self.len(),
-                index
-            )
-        }
-    }
-}
-
-impl<'lua> MultiValue<'lua> {
-    #[inline]
-    pub fn from_vec(mut vec: Vec<Value<'lua>>) -> MultiValue<'lua> {
-        vec.reverse();
-        MultiValue { vec, lua: None }
-    }
-
-    #[inline]
-    pub fn into_vec(mut self) -> Vec<Value<'lua>> {
-        let mut vec = mem::take(&mut self.vec);
-        mem::forget(self);
-        vec.reverse();
-        vec
-    }
-
-    #[inline]
-    pub fn get(&self, index: usize) -> Option<&Value<'lua>> {
-        if index < self.vec.len() {
-            return self.vec.get(self.vec.len() - index - 1);
-        }
-        None
-    }
-
-    #[inline]
-    pub fn pop_front(&mut self) -> Option<Value<'lua>> {
-        self.vec.pop()
-    }
-
-    #[inline]
-    pub fn push_front(&mut self, value: Value<'lua>) {
-        self.vec.push(value);
-    }
-
-    #[inline]
-    pub fn clear(&mut self) {
-        self.vec.clear();
-    }
-
-    #[inline]
-    pub fn len(&self) -> usize {
-        self.vec.len()
-    }
-
-    #[inline]
-    pub fn is_empty(&self) -> bool {
-        self.vec.is_empty()
-    }
-
-    #[inline]
-    pub fn iter(&self) -> iter::Rev<slice::Iter<Value<'lua>>> {
-        self.vec.iter().rev()
-    }
-
-    #[inline]
-    pub(crate) fn drain_all(&mut self) -> iter::Rev<vec::Drain<Value<'lua>>> {
-        self.vec.drain(..).rev()
-    }
-
-    #[inline]
-    pub(crate) fn refill(
-        &mut self,
-        iter: impl IntoIterator<Item = Result<Value<'lua>>>,
-    ) -> Result<()> {
-        self.vec.clear();
-        for value in iter {
-            self.vec.push(value?);
-        }
-        self.vec.reverse();
-        Ok(())
+        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<'lua>: Sized {
+/// 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 Lua) -> Result<MultiValue<'lua>>;
+    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: &'lua Lua) -> Result<c_int> {
-        let mut values = self.into_lua_multi(lua)?;
+    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 v in values.drain_all() {
-                lua.push_value(v)?;
+            for val in &values {
+                lua.push_value(val)?;
             }
         }
         Ok(len)
@@ -947,14 +849,14 @@ pub trait IntoLuaMulti<'lua>: Sized {
 ///
 /// 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<'lua>: Sized {
+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: &'lua Lua) -> Result<Self>;
+    fn from_lua_multi(values: MultiValue, lua: &Lua) -> Result<Self>;
 
     /// Performs the conversion for a list of arguments.
     ///
@@ -962,12 +864,7 @@ pub trait FromLuaMulti<'lua>: Sized {
     /// `to` is a function name that received the arguments.
     #[doc(hidden)]
     #[inline]
-    fn from_lua_args(
-        args: MultiValue<'lua>,
-        i: usize,
-        to: Option<&str>,
-        lua: &'lua Lua,
-    ) -> Result<Self> {
+    fn from_lua_args(args: MultiValue, i: usize, to: Option<&str>, lua: &Lua) -> Result<Self> {
         let _ = (i, to);
         Self::from_lua_multi(args, lua)
     }
@@ -975,27 +872,22 @@ pub trait FromLuaMulti<'lua>: Sized {
     /// Performs the conversion for a number of values in the Lua stack.
     #[doc(hidden)]
     #[inline]
-    unsafe fn from_stack_multi(nvals: c_int, lua: &'lua Lua) -> Result<Self> {
-        let mut values = MultiValue::with_lua_and_capacity(lua, nvals as usize);
-        for idx in 1..=nvals {
-            values.push_front(lua.stack_value(-idx));
+    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)
+        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: &'lua Lua,
-    ) -> Result<Self> {
+    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)
     }
@@ -1005,6 +897,13 @@ pub trait FromLuaMulti<'lua>: Sized {
 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);
 }

tarpaulin.toml

@@ -1,8 +1,8 @@
 [lua54_coverage]
-features = "lua54,vendored,async,serialize,macros,unstable"
+features = "lua54,vendored,async,serialize,macros"
 
 [lua51_coverage]
-features = "lua51,vendored,async,serialize,macros,unstable"
+features = "lua51,vendored,async,serialize,macros"
 
 [luau_coverage]
-features = "luau,async,serialize,macros,unstable"
+features = "luau,async,serialize,macros"

tests/async.rs

@@ -1,13 +1,14 @@
 #![cfg(feature = "async")]
 
-use std::sync::{Arc, Mutex};
+use std::sync::Arc;
 use std::time::Duration;
 
 use futures_util::stream::TryStreamExt;
+use tokio::sync::Mutex;
 
 use mlua::{
-    AnyUserDataExt, Error, Function, Lua, LuaOptions, MultiValue, Result, StdLib, Table, TableExt,
-    UserData, UserDataMethods, Value,
+    Error, Function, Lua, LuaOptions, MultiValue, ObjectLike, Result, StdLib, Table, UserData,
+    UserDataMethods, Value,
 };
 
 #[cfg(not(target_arch = "wasm32"))]
@@ -25,8 +26,7 @@ async fn sleep_ms(_ms: u64) {
 async fn test_async_function() -> Result<()> {
     let lua = Lua::new();
 
-    let f = lua
-        .create_async_function(|_lua, (a, b, c): (i64, i64, i64)| async move { Ok((a + b) * c) })?;
+    let f = lua.create_async_function(|_lua, (a, b, c): (i64, i64, i64)| async move { Ok((a + b) * c) })?;
     lua.globals().set("f", f)?;
 
     let res: i64 = lua.load("f(1, 2, 3)").eval_async().await?;
@@ -73,18 +73,16 @@ async fn test_async_call() -> Result<()> {
         Ok(format!("hello, {}!", name))
     })?;
 
-    match hello.call::<_, ()>("alex") {
+    match hello.call::<()>("alex") {
         Err(Error::RuntimeError(_)) => {}
-        _ => panic!(
-            "non-async executing async function must fail on the yield stage with RuntimeError"
-        ),
+        err => panic!("expected `RuntimeError`, got {err:?}"),
     };
 
-    assert_eq!(hello.call_async::<_, String>("alex").await?, "hello, alex!");
+    assert_eq!(hello.call_async::<String>("alex").await?, "hello, alex!");
 
     // Executing non-async functions using async call is allowed
     let sum = lua.create_function(|_lua, (a, b): (i64, i64)| return Ok(a + b))?;
-    assert_eq!(sum.call_async::<_, i64>((5, 1)).await?, 6);
+    assert_eq!(sum.call_async::<i64>((5, 1)).await?, 6);
 
     Ok(())
 }
@@ -98,7 +96,7 @@ async fn test_async_call_many_returns() -> Result<()> {
         Ok(("a", "b", "c", 1))
     })?;
 
-    let vals = hello.call_async::<_, MultiValue>(()).await?;
+    let vals = hello.call_async::<MultiValue>(()).await?;
     assert_eq!(vals.len(), 4);
     assert_eq!(vals[0].to_string()?, "a");
     assert_eq!(vals[1].to_string()?, "b");
@@ -161,7 +159,7 @@ async fn test_async_handle_yield() -> Result<()> {
     "#,
         )
         .eval::<Function>()?;
-    assert_eq!(min.call_async::<_, i64>((-1, 1)).await?, -1);
+    assert_eq!(min.call_async::<i64>((-1, 1)).await?, -1);
 
     Ok(())
 }
@@ -230,15 +228,15 @@ async fn test_async_lua54_to_be_closed() -> Result<()> {
     let f = lua.load(code).into_function()?;
 
     // Test close using call_async
-    let _ = f.call_async::<_, ()>(()).await;
-    assert_eq!(globals.get::<_, usize>("close_count")?, 1);
+    let _ = f.call_async::<()>(()).await;
+    assert_eq!(globals.get::<usize>("close_count")?, 1);
 
     // Don't close by default when awaiting async threads
     let co = lua.create_thread(f.clone())?;
-    let _ = co.clone().into_async::<_, ()>(()).await;
-    assert_eq!(globals.get::<_, usize>("close_count")?, 1);
+    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);
+    assert_eq!(globals.get::<usize>("close_count")?, 2);
 
     Ok(())
 }
@@ -262,7 +260,7 @@ 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;
@@ -310,14 +308,14 @@ fn test_async_thread_capture() -> Result<()> {
 
     let thread = lua.create_thread(f)?;
     // After first resume, `v: Value` is captured in the coroutine
-    thread.resume::<_, ()>("abc").unwrap();
+    thread.resume::<()>("abc").unwrap();
     drop(thread);
 
     Ok(())
 }
 
 #[tokio::test]
-async fn test_async_table() -> Result<()> {
+async fn test_async_table_object_like() -> Result<()> {
     let options = LuaOptions::new().thread_pool_size(4);
     let lua = Lua::new_with(StdLib::ALL_SAFE, options)?;
 
@@ -326,7 +324,7 @@ async fn test_async_table() -> Result<()> {
 
     let get_value = lua.create_async_function(|_, table: Table| async move {
         sleep_ms(10).await;
-        table.get::<_, i64>("val")
+        table.get::<i64>("val")
     })?;
     table.set("get_value", get_value)?;
 
@@ -336,25 +334,20 @@ async fn test_async_table() -> Result<()> {
     })?;
     table.set("set_value", set_value)?;
 
-    let sleep = lua.create_async_function(|_, n| async move {
-        sleep_ms(n).await;
-        Ok(format!("elapsed:{}ms", n))
-    })?;
-    table.set("sleep", sleep)?;
+    assert_eq!(table.call_async_method::<i64>("get_value", ()).await?, 10);
+    table.call_async_method::<()>("set_value", 15).await?;
+    assert_eq!(table.call_async_method::<i64>("get_value", ()).await?, 15);
 
-    assert_eq!(
-        table.call_async_method::<_, i64>("get_value", ()).await?,
-        10
-    );
-    table.call_async_method("set_value", 15).await?;
-    assert_eq!(
-        table.call_async_method::<_, i64>("get_value", ()).await?,
-        15
-    );
-    assert_eq!(
-        table.call_async_function::<_, String>("sleep", 7).await?,
-        "elapsed:7ms"
-    );
+    let metatable = lua.create_table()?;
+    metatable.set(
+        "__call",
+        lua.create_async_function(|_, table: Table| async move {
+            sleep_ms(10).await;
+            table.get::<i64>("val")
+        })?,
+    )?;
+    table.set_metatable(Some(metatable));
+    assert_eq!(table.call_async::<i64>(()).await.unwrap(), 15);
 
     Ok(())
 }
@@ -374,9 +367,9 @@ async fn test_async_thread_pool() -> Result<()> {
         Ok(format!("elapsed:{}ms", n))
     })?;
 
-    assert!(error_f.call_async::<_, ()>(()).await.is_err());
+    assert!(error_f.call_async::<()>(()).await.is_err());
     // Next call should use cached thread
-    assert_eq!(sleep.call_async::<_, String>(3).await?, "elapsed:3ms");
+    assert_eq!(sleep.call_async::<String>(3).await?, "elapsed:3ms");
 
     Ok(())
 }
@@ -386,13 +379,13 @@ async fn test_async_userdata() -> Result<()> {
     struct MyUserData(u64);
 
     impl UserData for MyUserData {
-        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+        fn add_methods<M: UserDataMethods<Self>>(methods: &mut M) {
             methods.add_async_method("get_value", |_, data, ()| async move {
                 sleep_ms(10).await;
                 Ok(data.0)
             });
 
-            methods.add_async_method_mut("set_value", |_, data, n| async move {
+            methods.add_async_method_mut("set_value", |_, mut data, n| async move {
                 sleep_ms(10).await;
                 data.0 = n;
                 Ok(())
@@ -411,22 +404,19 @@ async fn test_async_userdata() -> Result<()> {
             });
 
             #[cfg(not(any(feature = "lua51", feature = "luau")))]
-            methods.add_async_meta_method(
-                mlua::MetaMethod::Index,
-                |_, data, key: String| async move {
-                    sleep_ms(10).await;
-                    match key.as_str() {
-                        "ms" => Ok(Some(data.0 as f64)),
-                        "s" => Ok(Some((data.0 as f64) / 1000.0)),
-                        _ => Ok(None),
-                    }
-                },
-            );
+            methods.add_async_meta_method(mlua::MetaMethod::Index, |_, data, key: String| async move {
+                sleep_ms(10).await;
+                match key.as_str() {
+                    "ms" => Ok(Some(data.0 as f64)),
+                    "s" => Ok(Some((data.0 as f64) / 1000.0)),
+                    _ => Ok(None),
+                }
+            });
 
             #[cfg(not(any(feature = "lua51", feature = "luau")))]
             methods.add_async_meta_method_mut(
                 mlua::MetaMethod::NewIndex,
-                |_, data, (key, value): (String, f64)| async move {
+                |_, mut data, (key, value): (String, f64)| async move {
                     sleep_ms(10).await;
                     match key.as_str() {
                         "ms" => data.0 = value as u64,
@@ -443,7 +433,7 @@ async fn test_async_userdata() -> Result<()> {
     let globals = lua.globals();
 
     let userdata = lua.create_userdata(MyUserData(11))?;
-    globals.set("userdata", userdata.clone())?;
+    globals.set("userdata", &userdata)?;
 
     lua.load(
         r#"
@@ -472,13 +462,14 @@ async fn test_async_userdata() -> Result<()> {
     .exec_async()
     .await?;
 
-    userdata.call_async_method("set_value", 24).await?;
+    // ObjectLike methods
+    userdata.call_async_method::<()>("set_value", 24).await?;
     let n: u64 = userdata.call_async_method("get_value", ()).await?;
     assert_eq!(n, 24);
-    userdata.call_async_function("sleep", 15).await?;
+    userdata.call_async_function::<()>("sleep", 15).await?;
 
     #[cfg(not(any(feature = "lua51", feature = "luau")))]
-    assert_eq!(userdata.call_async::<_, String>(()).await?, "elapsed:24ms");
+    assert_eq!(userdata.call_async::<String>(()).await?, "elapsed:24ms");
 
     Ok(())
 }
@@ -488,7 +479,7 @@ async fn test_async_thread_error() -> Result<()> {
     struct MyUserData;
 
     impl UserData for MyUserData {
-        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+        fn add_methods<M: UserDataMethods<Self>>(methods: &mut M) {
             methods.add_meta_method("__tostring", |_, _this, ()| Ok("myuserdata error"))
         }
     }
@@ -497,7 +488,7 @@ async fn test_async_thread_error() -> Result<()> {
     let result = lua
         .load("function x(...) error(...) end x(...)")
         .set_name("chunk")
-        .call_async::<_, ()>(MyUserData)
+        .call_async::<()>(MyUserData)
         .await;
     assert!(
         matches!(result, Err(Error::RuntimeError(cause)) if cause.contains("myuserdata error")),
@@ -507,41 +498,24 @@ async fn test_async_thread_error() -> Result<()> {
     Ok(())
 }
 
-#[cfg(all(feature = "unstable", not(feature = "send")))]
-#[tokio::test]
-async fn test_owned_async_call() -> Result<()> {
-    let lua = Lua::new();
-
-    let hello = lua
-        .create_async_function(|_, name: String| async move {
-            sleep_ms(10).await;
-            Ok(format!("hello, {}!", name))
-        })?
-        .into_owned();
-    drop(lua);
-
-    assert_eq!(hello.call_async::<_, String>("alex").await?, "hello, alex!");
-
-    Ok(())
-}
-
 #[tokio::test]
 async fn test_async_terminate() -> Result<()> {
-    let lua = Lua::new();
-
     let mutex = Arc::new(Mutex::new(0u32));
-    let mutex2 = mutex.clone();
-    let func = lua.create_async_function(move |_, ()| {
-        let mutex = mutex2.clone();
-        async move {
-            let _guard = mutex.lock();
-            sleep_ms(100).await;
-            Ok(())
-        }
-    })?;
+    {
+        let lua = Lua::new();
+        let mutex2 = mutex.clone();
+        let func = lua.create_async_function(move |lua, ()| {
+            let mutex = mutex2.clone();
+            async move {
+                let _guard = mutex.lock().await;
+                sleep_ms(100).await;
+                drop(lua); // Move Lua to the future to test drop
+                Ok(())
+            }
+        })?;
 
-    let _ = tokio::time::timeout(Duration::from_millis(30), func.call_async::<_, ()>(())).await;
-    lua.gc_collect()?;
+        let _ = tokio::time::timeout(Duration::from_millis(30), func.call_async::<()>(())).await;
+    }
     assert!(mutex.try_lock().is_ok());
 
     Ok(())

tests/byte_string.rs

@@ -22,38 +22,38 @@ fn test_byte_string_round_trip() -> Result<()> {
 
     let globals = lua.globals();
 
-    let isi = globals.get::<_, BString>("invalid_sequence_identifier")?;
+    let isi = globals.get::<BString>("invalid_sequence_identifier")?;
     assert_eq!(isi, [0xa0, 0xa1].as_ref());
 
-    let i2os2 = globals.get::<_, BString>("invalid_2_octet_sequence_2nd")?;
+    let i2os2 = globals.get::<BString>("invalid_2_octet_sequence_2nd")?;
     assert_eq!(i2os2, [0xc3, 0x28].as_ref());
 
-    let i3os2 = globals.get::<_, BString>("invalid_3_octet_sequence_2nd")?;
+    let i3os2 = globals.get::<BString>("invalid_3_octet_sequence_2nd")?;
     assert_eq!(i3os2, [0xe2, 0x28, 0xa1].as_ref());
 
-    let i3os3 = globals.get::<_, BString>("invalid_3_octet_sequence_3rd")?;
+    let i3os3 = globals.get::<BString>("invalid_3_octet_sequence_3rd")?;
     assert_eq!(i3os3, [0xe2, 0x82, 0x28].as_ref());
 
-    let i4os2 = globals.get::<_, BString>("invalid_4_octet_sequence_2nd")?;
+    let i4os2 = globals.get::<BString>("invalid_4_octet_sequence_2nd")?;
     assert_eq!(i4os2, [0xf0, 0x28, 0x8c, 0xbc].as_ref());
 
-    let i4os3 = globals.get::<_, BString>("invalid_4_octet_sequence_3rd")?;
+    let i4os3 = globals.get::<BString>("invalid_4_octet_sequence_3rd")?;
     assert_eq!(i4os3, [0xf0, 0x90, 0x28, 0xbc].as_ref());
 
-    let i4os4 = globals.get::<_, BString>("invalid_4_octet_sequence_4th")?;
+    let i4os4 = globals.get::<BString>("invalid_4_octet_sequence_4th")?;
     assert_eq!(i4os4, [0xf0, 0x28, 0x8c, 0x28].as_ref());
 
-    let aas = globals.get::<_, BString>("an_actual_string")?;
+    let aas = globals.get::<BString>("an_actual_string")?;
     assert_eq!(aas, b"Hello, world!".as_ref());
 
-    globals.set::<_, &BStr>("bstr_invalid_sequence_identifier", isi.as_ref())?;
-    globals.set::<_, &BStr>("bstr_invalid_2_octet_sequence_2nd", i2os2.as_ref())?;
-    globals.set::<_, &BStr>("bstr_invalid_3_octet_sequence_2nd", i3os2.as_ref())?;
-    globals.set::<_, &BStr>("bstr_invalid_3_octet_sequence_3rd", i3os3.as_ref())?;
-    globals.set::<_, &BStr>("bstr_invalid_4_octet_sequence_2nd", i4os2.as_ref())?;
-    globals.set::<_, &BStr>("bstr_invalid_4_octet_sequence_3rd", i4os3.as_ref())?;
-    globals.set::<_, &BStr>("bstr_invalid_4_octet_sequence_4th", i4os4.as_ref())?;
-    globals.set::<_, &BStr>("bstr_an_actual_string", aas.as_ref())?;
+    globals.set("bstr_invalid_sequence_identifier", isi.as_ref() as &BStr)?;
+    globals.set("bstr_invalid_2_octet_sequence_2nd", i2os2.as_ref() as &BStr)?;
+    globals.set("bstr_invalid_3_octet_sequence_2nd", i3os2.as_ref() as &BStr)?;
+    globals.set("bstr_invalid_3_octet_sequence_3rd", i3os3.as_ref() as &BStr)?;
+    globals.set("bstr_invalid_4_octet_sequence_2nd", i4os2.as_ref() as &BStr)?;
+    globals.set("bstr_invalid_4_octet_sequence_3rd", i4os3.as_ref() as &BStr)?;
+    globals.set("bstr_invalid_4_octet_sequence_4th", i4os4.as_ref() as &BStr)?;
+    globals.set("bstr_an_actual_string", aas.as_ref() as &BStr)?;
 
     lua.load(
         r#"
@@ -69,14 +69,14 @@ fn test_byte_string_round_trip() -> Result<()> {
     )
     .exec()?;
 
-    globals.set::<_, BString>("bstring_invalid_sequence_identifier", isi)?;
-    globals.set::<_, BString>("bstring_invalid_2_octet_sequence_2nd", i2os2)?;
-    globals.set::<_, BString>("bstring_invalid_3_octet_sequence_2nd", i3os2)?;
-    globals.set::<_, BString>("bstring_invalid_3_octet_sequence_3rd", i3os3)?;
-    globals.set::<_, BString>("bstring_invalid_4_octet_sequence_2nd", i4os2)?;
-    globals.set::<_, BString>("bstring_invalid_4_octet_sequence_3rd", i4os3)?;
-    globals.set::<_, BString>("bstring_invalid_4_octet_sequence_4th", i4os4)?;
-    globals.set::<_, BString>("bstring_an_actual_string", aas)?;
+    globals.set("bstring_invalid_sequence_identifier", isi)?;
+    globals.set("bstring_invalid_2_octet_sequence_2nd", i2os2)?;
+    globals.set("bstring_invalid_3_octet_sequence_2nd", i3os2)?;
+    globals.set("bstring_invalid_3_octet_sequence_3rd", i3os3)?;
+    globals.set("bstring_invalid_4_octet_sequence_2nd", i4os2)?;
+    globals.set("bstring_invalid_4_octet_sequence_3rd", i4os3)?;
+    globals.set("bstring_invalid_4_octet_sequence_4th", i4os4)?;
+    globals.set("bstring_an_actual_string", aas)?;
 
     lua.load(
         r#"

tests/chunk.rs

@@ -1,5 +1,4 @@
-use std::fs;
-use std::io;
+use std::{fs, io};
 
 use mlua::{Lua, Result};
 
@@ -65,7 +64,7 @@ fn test_chunk_macro() -> Result<()> {
     })
     .exec()?;
 
-    assert_eq!(lua.globals().get::<_, i32>("s")?, 321);
+    assert_eq!(lua.globals().get::<i32>("s")?, 321);
 
     Ok(())
 }

tests/compile.rs

@@ -12,7 +12,6 @@ fn test_compilation() {
     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");
-    t.compile_fail("tests/compile/static_callback_args.rs");
 
     #[cfg(feature = "async")]
     {

tests/compile/async_any_userdata_method.stderr

@@ -1,10 +1,18 @@
+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
+   |
+9  |         reg.add_async_method("t", |_, this: &String, ()| 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
    |
 9  |           reg.add_async_method("t", |_, this: &String, ()| async {
    |  ___________________________________----------------------_^
    | |                                   |                    |
-   | |                                   |                    return type of closure `[async block@$DIR/tests/compile/async_any_userdata_method.rs:9:58: 12:10]` contains a lifetime `'2`
+   | |                                   |                    return type of closure `{async block@$DIR/tests/compile/async_any_userdata_method.rs:9:58: 9:63}` contains a lifetime `'2`
    | |                                   lifetime `'1` represents this closure's body
 10 | |             s = this;
 11 | |             Ok(())
@@ -13,20 +21,11 @@ error: lifetime may not live long enough
    |
    = note: closure implements `Fn`, so references to captured variables can't escape the closure
 
-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
-   |
-9  |           reg.add_async_method("t", |_, this: &String, ()| async {
-   |  __________________________________________________________^
-10 | |             s = this;
-   | |             - mutable borrow occurs due to use of `s` in closure
-11 | |             Ok(())
-12 | |         });
-   | |_________^ cannot borrow as mutable
-
 error[E0597]: `s` does not live long enough
   --> tests/compile/async_any_userdata_method.rs:8:21
    |
+7  |           let s = String::new();
+   |               - 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 {

tests/compile/lua_norefunwindsafe.stderr

@@ -1,27 +1,78 @@
-error[E0277]: the type `UnsafeCell<mlua::lua::ExtraData>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+error[E0277]: the type `UnsafeCell<*mut lua_State>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
  --> tests/compile/lua_norefunwindsafe.rs:7:18
   |
 7 |     catch_unwind(|| lua.create_table().unwrap());
-  |     ------------ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `UnsafeCell<mlua::lua::ExtraData>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+  |     ------------ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `UnsafeCell<*mut lua_State>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
   |     |
   |     required by a bound introduced by this call
   |
-  = help: within `Lua`, the trait `RefUnwindSafe` is not implemented for `UnsafeCell<mlua::lua::ExtraData>`
-  = note: required because it appears within the type `ArcInner<UnsafeCell<ExtraData>>`
-  = note: required because it appears within the type `PhantomData<ArcInner<UnsafeCell<ExtraData>>>`
-  = note: required because it appears within the type `Arc<UnsafeCell<ExtraData>>`
-  = note: required because it appears within the type `LuaInner`
-  = note: required because it appears within the type `ArcInner<LuaInner>`
-  = note: required because it appears within the type `PhantomData<ArcInner<LuaInner>>`
-  = note: required because it appears within the type `Arc<LuaInner>`
-  = note: required because it appears within the type `Lua`
+  = 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`
+note: required because it appears within the type `Cell<*mut lua_State>`
+ --> $RUST/core/src/cell.rs
+  |
+  | pub struct Cell<T: ?Sized> {
+  |            ^^^^
+note: required because it appears within the type `mlua::state::raw::RawLua`
+ --> src/state/raw.rs
+  |
+  | pub struct RawLua {
+  |            ^^^^^^
+note: required because it appears within the type `mlua::types::sync::inner::ReentrantMutex<mlua::state::raw::RawLua>`
+ --> src/types/sync.rs
+  |
+  |     pub(crate) struct ReentrantMutex<T>(T);
+  |                       ^^^^^^^^^^^^^^
+  = note: required for `Rc<mlua::types::sync::inner::ReentrantMutex<mlua::state::raw::RawLua>>` to implement `RefUnwindSafe`
+note: required because it appears within the type `Lua`
+ --> src/state.rs
+  |
+  | pub struct Lua(XRc<ReentrantMutex<RawLua>>);
+  |            ^^^
   = note: required for `&Lua` to implement `UnwindSafe`
 note: required because it's used within this closure
  --> tests/compile/lua_norefunwindsafe.rs:7:18
   |
 7 |     catch_unwind(|| lua.create_table().unwrap());
   |                  ^^
-note: required by a bound in `catch_unwind`
+note: required by a bound in `std::panic::catch_unwind`
+ --> $RUST/std/src/panic.rs
+  |
+  | pub fn catch_unwind<F: FnOnce() -> R + UnwindSafe, R>(f: F) -> Result<R> {
+  |                                        ^^^^^^^^^^ required by this bound in `catch_unwind`
+
+error[E0277]: the type `UnsafeCell<mlua::state::extra::ExtraData>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+ --> tests/compile/lua_norefunwindsafe.rs:7:18
+  |
+7 |     catch_unwind(|| lua.create_table().unwrap());
+  |     ------------ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `UnsafeCell<mlua::state::extra::ExtraData>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+  |     |
+  |     required by a bound introduced by this call
+  |
+  = help: the trait `RefUnwindSafe` is not implemented for `UnsafeCell<mlua::state::extra::ExtraData>`, which is required by `{closure@$DIR/tests/compile/lua_norefunwindsafe.rs:7:18: 7:20}: UnwindSafe`
+  = 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
+  |
+  | pub struct RawLua {
+  |            ^^^^^^
+note: required because it appears within the type `mlua::types::sync::inner::ReentrantMutex<mlua::state::raw::RawLua>`
+ --> src/types/sync.rs
+  |
+  |     pub(crate) struct ReentrantMutex<T>(T);
+  |                       ^^^^^^^^^^^^^^
+  = note: required for `Rc<mlua::types::sync::inner::ReentrantMutex<mlua::state::raw::RawLua>>` to implement `RefUnwindSafe`
+note: required because it appears within the type `Lua`
+ --> src/state.rs
+  |
+  | pub struct Lua(XRc<ReentrantMutex<RawLua>>);
+  |            ^^^
+  = note: required for `&Lua` to implement `UnwindSafe`
+note: required because it's used within this closure
+ --> tests/compile/lua_norefunwindsafe.rs:7:18
+  |
+7 |     catch_unwind(|| lua.create_table().unwrap());
+  |                  ^^
+note: required by a bound in `std::panic::catch_unwind`
  --> $RUST/std/src/panic.rs
   |
   | pub fn catch_unwind<F: FnOnce() -> R + UnwindSafe, R>(f: F) -> Result<R> {

tests/compile/non_send.rs

@@ -11,7 +11,7 @@ fn main() -> Result<()> {
     lua.create_function(move |_, ()| {
         Ok(data.get())
     })?
-    .call::<_, i32>(())?;
+    .call::<i32>(())?;
 
     Ok(())
 }

tests/compile/non_send.stderr

@@ -4,22 +4,25 @@ error[E0277]: `Rc<Cell<i32>>` cannot be sent between threads safely
 11 |       lua.create_function(move |_, ()| {
    |           --------------- ^-----------
    |           |               |
-   |  _________|_______________within this `[closure@$DIR/tests/compile/non_send.rs:11:25: 11:37]`
+   |  _________|_______________within this `{closure@$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
    |
-   = help: within `[closure@$DIR/tests/compile/non_send.rs:11:25: 11:37]`, the trait `Send` is not implemented for `Rc<Cell<i32>>`
+   = help: within `{closure@$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 |_, ()| {
    |                         ^^^^^^^^^^^^
-   = 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 `mlua::types::MaybeSend`
 note: required by a bound in `Lua::create_function`
   --> src/lua.rs
    |
+   |     pub fn create_function<'lua, A, R, F>(&'lua self, func: F) -> Result<Function<'lua>>
+   |            --------------- 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`

tests/compile/ref_nounwindsafe.stderr

@@ -1,29 +1,167 @@
-error[E0277]: the type `UnsafeCell<mlua::lua::ExtraData>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+error[E0277]: the type `UnsafeCell<usize>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
  --> tests/compile/ref_nounwindsafe.rs:8:18
   |
 8 |     catch_unwind(move || table.set("a", "b").unwrap());
-  |     ------------ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `UnsafeCell<mlua::lua::ExtraData>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+  |     ------------ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `UnsafeCell<usize>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
   |     |
   |     required by a bound introduced by this call
   |
-  = help: within `Lua`, the trait `RefUnwindSafe` is not implemented for `UnsafeCell<mlua::lua::ExtraData>`
-  = note: required because it appears within the type `ArcInner<UnsafeCell<ExtraData>>`
-  = note: required because it appears within the type `PhantomData<ArcInner<UnsafeCell<ExtraData>>>`
-  = note: required because it appears within the type `Arc<UnsafeCell<ExtraData>>`
-  = note: required because it appears within the type `LuaInner`
-  = note: required because it appears within the type `ArcInner<LuaInner>`
-  = note: required because it appears within the type `PhantomData<ArcInner<LuaInner>>`
-  = note: required because it appears within the type `Arc<LuaInner>`
-  = note: required because it appears within the type `Lua`
-  = note: required for `&Lua` to implement `UnwindSafe`
-  = note: required because it appears within the type `LuaRef<'_>`
-  = note: required because it appears within the type `Table<'_>`
+  = help: within `rc::RcBox<mlua::types::sync::inner::ReentrantMutex<mlua::state::raw::RawLua>>`, the trait `RefUnwindSafe` is not implemented for `UnsafeCell<usize>`, which is required by `{closure@$DIR/tests/compile/ref_nounwindsafe.rs:8:18: 8:25}: UnwindSafe`
+note: required because it appears within the type `Cell<usize>`
+ --> $RUST/core/src/cell.rs
+  |
+  | pub struct Cell<T: ?Sized> {
+  |            ^^^^
+note: required because it appears within the type `rc::RcBox<mlua::types::sync::inner::ReentrantMutex<mlua::state::raw::RawLua>>`
+ --> $RUST/alloc/src/rc.rs
+  |
+  | struct RcBox<T: ?Sized> {
+  |        ^^^^^
+  = note: required for `NonNull<rc::RcBox<mlua::types::sync::inner::ReentrantMutex<mlua::state::raw::RawLua>>>` to implement `UnwindSafe`
+note: required because it appears within the type `std::rc::Weak<mlua::types::sync::inner::ReentrantMutex<mlua::state::raw::RawLua>>`
+ --> $RUST/alloc/src/rc.rs
+  |
+  | pub struct Weak<
+  |            ^^^^
+note: required because it appears within the type `mlua::state::WeakLua`
+ --> src/state.rs
+  |
+  | pub(crate) struct WeakLua(XWeak<ReentrantMutex<RawLua>>);
+  |                   ^^^^^^^
+note: required because it appears within the type `mlua::types::ValueRef`
+ --> src/types.rs
+  |
+  | pub(crate) struct ValueRef {
+  |                   ^^^^^^^^
+note: required because it appears within the type `LuaTable`
+ --> src/table.rs
+  |
+  | pub struct Table(pub(crate) ValueRef);
+  |            ^^^^^
 note: required because it's used within this closure
  --> tests/compile/ref_nounwindsafe.rs:8:18
   |
 8 |     catch_unwind(move || table.set("a", "b").unwrap());
   |                  ^^^^^^^
-note: required by a bound in `catch_unwind`
+note: required by a bound in `std::panic::catch_unwind`
+ --> $RUST/std/src/panic.rs
+  |
+  | pub fn catch_unwind<F: FnOnce() -> R + UnwindSafe, R>(f: F) -> Result<R> {
+  |                                        ^^^^^^^^^^ required by this bound in `catch_unwind`
+
+error[E0277]: the type `UnsafeCell<*mut lua_State>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+ --> tests/compile/ref_nounwindsafe.rs:8:18
+  |
+8 |     catch_unwind(move || table.set("a", "b").unwrap());
+  |     ------------ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `UnsafeCell<*mut lua_State>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+  |     |
+  |     required by a bound introduced by this call
+  |
+  = help: within `rc::RcBox<mlua::types::sync::inner::ReentrantMutex<mlua::state::raw::RawLua>>`, the trait `RefUnwindSafe` is not implemented for `UnsafeCell<*mut lua_State>`, which is required by `{closure@$DIR/tests/compile/ref_nounwindsafe.rs:8:18: 8:25}: UnwindSafe`
+note: required because it appears within the type `Cell<*mut lua_State>`
+ --> $RUST/core/src/cell.rs
+  |
+  | pub struct Cell<T: ?Sized> {
+  |            ^^^^
+note: required because it appears within the type `mlua::state::raw::RawLua`
+ --> src/state/raw.rs
+  |
+  | pub struct RawLua {
+  |            ^^^^^^
+note: required because it appears within the type `mlua::types::sync::inner::ReentrantMutex<mlua::state::raw::RawLua>`
+ --> src/types/sync.rs
+  |
+  |     pub(crate) struct ReentrantMutex<T>(T);
+  |                       ^^^^^^^^^^^^^^
+note: required because it appears within the type `rc::RcBox<mlua::types::sync::inner::ReentrantMutex<mlua::state::raw::RawLua>>`
+ --> $RUST/alloc/src/rc.rs
+  |
+  | struct RcBox<T: ?Sized> {
+  |        ^^^^^
+  = note: required for `NonNull<rc::RcBox<mlua::types::sync::inner::ReentrantMutex<mlua::state::raw::RawLua>>>` to implement `UnwindSafe`
+note: required because it appears within the type `std::rc::Weak<mlua::types::sync::inner::ReentrantMutex<mlua::state::raw::RawLua>>`
+ --> $RUST/alloc/src/rc.rs
+  |
+  | pub struct Weak<
+  |            ^^^^
+note: required because it appears within the type `mlua::state::WeakLua`
+ --> src/state.rs
+  |
+  | pub(crate) struct WeakLua(XWeak<ReentrantMutex<RawLua>>);
+  |                   ^^^^^^^
+note: required because it appears within the type `mlua::types::ValueRef`
+ --> src/types.rs
+  |
+  | pub(crate) struct ValueRef {
+  |                   ^^^^^^^^
+note: required because it appears within the type `LuaTable`
+ --> src/table.rs
+  |
+  | pub struct Table(pub(crate) ValueRef);
+  |            ^^^^^
+note: required because it's used within this closure
+ --> tests/compile/ref_nounwindsafe.rs:8:18
+  |
+8 |     catch_unwind(move || table.set("a", "b").unwrap());
+  |                  ^^^^^^^
+note: required by a bound in `std::panic::catch_unwind`
+ --> $RUST/std/src/panic.rs
+  |
+  | pub fn catch_unwind<F: FnOnce() -> R + UnwindSafe, R>(f: F) -> Result<R> {
+  |                                        ^^^^^^^^^^ required by this bound in `catch_unwind`
+
+error[E0277]: the type `UnsafeCell<mlua::state::extra::ExtraData>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+ --> tests/compile/ref_nounwindsafe.rs:8:18
+  |
+8 |     catch_unwind(move || table.set("a", "b").unwrap());
+  |     ------------ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `UnsafeCell<mlua::state::extra::ExtraData>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+  |     |
+  |     required by a bound introduced by this call
+  |
+  = help: the trait `RefUnwindSafe` is not implemented for `UnsafeCell<mlua::state::extra::ExtraData>`, which is required by `{closure@$DIR/tests/compile/ref_nounwindsafe.rs:8:18: 8:25}: UnwindSafe`
+  = 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
+  |
+  | pub struct RawLua {
+  |            ^^^^^^
+note: required because it appears within the type `mlua::types::sync::inner::ReentrantMutex<mlua::state::raw::RawLua>`
+ --> src/types/sync.rs
+  |
+  |     pub(crate) struct ReentrantMutex<T>(T);
+  |                       ^^^^^^^^^^^^^^
+note: required because it appears within the type `rc::RcBox<mlua::types::sync::inner::ReentrantMutex<mlua::state::raw::RawLua>>`
+ --> $RUST/alloc/src/rc.rs
+  |
+  | struct RcBox<T: ?Sized> {
+  |        ^^^^^
+  = note: required for `NonNull<rc::RcBox<mlua::types::sync::inner::ReentrantMutex<mlua::state::raw::RawLua>>>` to implement `UnwindSafe`
+note: required because it appears within the type `std::rc::Weak<mlua::types::sync::inner::ReentrantMutex<mlua::state::raw::RawLua>>`
+ --> $RUST/alloc/src/rc.rs
+  |
+  | pub struct Weak<
+  |            ^^^^
+note: required because it appears within the type `mlua::state::WeakLua`
+ --> src/state.rs
+  |
+  | pub(crate) struct WeakLua(XWeak<ReentrantMutex<RawLua>>);
+  |                   ^^^^^^^
+note: required because it appears within the type `mlua::types::ValueRef`
+ --> src/types.rs
+  |
+  | pub(crate) struct ValueRef {
+  |                   ^^^^^^^^
+note: required because it appears within the type `LuaTable`
+ --> src/table.rs
+  |
+  | pub struct Table(pub(crate) ValueRef);
+  |            ^^^^^
+note: required because it's used within this closure
+ --> tests/compile/ref_nounwindsafe.rs:8:18
+  |
+8 |     catch_unwind(move || table.set("a", "b").unwrap());
+  |                  ^^^^^^^
+note: required by a bound in `std::panic::catch_unwind`
  --> $RUST/std/src/panic.rs
   |
   | pub fn catch_unwind<F: FnOnce() -> R + UnwindSafe, R>(f: F) -> Result<R> {

tests/compile/scope_callback_capture.rs

@@ -12,7 +12,7 @@ fn main() {
                 inner = Some(t);
                 Ok(())
             })?;
-        f.call::<_, ()>(lua.create_table()?)?;
+        f.call::<()>(lua.create_table()?)?;
         Ok(())
     });
 }

tests/compile/scope_callback_capture.stderr

@@ -1,26 +1,5 @@
-warning: unused variable: `old`
- --> $DIR/scope_callback_capture.rs:9:29
+error[E0599]: no method named `scope` found for struct `Lua` in the current scope
+ --> tests/compile/scope_callback_capture.rs:5:9
   |
-9 |                 if let Some(old) = inner.take() {
-  |                             ^^^ help: if this is intentional, prefix it with an underscore: `_old`
-  |
-  = note: `#[warn(unused_variables)]` on by default
-
-error[E0521]: borrowed data escapes outside of closure
-  --> $DIR/scope_callback_capture.rs:7:17
-   |
-5  |       lua.scope(|scope| {
-   |                  -----
-   |                  |
-   |                  `scope` declared here, outside of the closure body
-   |                  `scope` is a reference that is only valid in the closure body
-6  |           let mut inner: Option<Table> = None;
-7  |           let f = scope
-   |  _________________^
-8  | |             .create_function_mut(move |_, t: Table| {
-9  | |                 if let Some(old) = inner.take() {
-10 | |                     // Access old callback `Lua`.
-...  |
-13 | |                 Ok(())
-14 | |             })?;
-   | |______________^ `scope` escapes the closure body here
+5 |     lua.scope(|scope| {
+  |     ----^^^^^ method not found in `Lua`

tests/compile/scope_callback_inner.rs

@@ -9,7 +9,7 @@ fn main() {
                 inner = Some(t);
                 Ok(())
             })?;
-        f.call::<_, ()>(lua.create_table()?)?;
+        f.call::<()>(lua.create_table()?)?;
         Ok(())
     });
 }

tests/compile/scope_callback_inner.stderr

@@ -1,42 +1,5 @@
-error[E0521]: borrowed data escapes outside of closure
-  --> tests/compile/scope_callback_inner.rs:7:17
-   |
-5  |       lua.scope(|scope| {
-   |                  -----
-   |                  |
-   |                  `scope` declared here, outside of the closure body
-   |                  `scope` is a reference that is only valid in the closure body
-6  |           let mut inner: Option<Table> = None;
-7  |           let f = scope
-   |  _________________^
-8  | |             .create_function_mut(|_, t: Table| {
-9  | |                 inner = Some(t);
-10 | |                 Ok(())
-11 | |             })?;
-   | |______________^ `scope` escapes the closure body here
-
-error[E0373]: closure may outlive the current function, but it borrows `inner`, which is owned by the current function
-  --> tests/compile/scope_callback_inner.rs:8:34
-   |
-5  |     lua.scope(|scope| {
-   |                ----- has type `&mlua::Scope<'_, '2>`
-...
-8  |             .create_function_mut(|_, t: Table| {
-   |                                  ^^^^^^^^^^^^^ may outlive borrowed value `inner`
-9  |                 inner = Some(t);
-   |                 ----- `inner` is borrowed here
-   |
-note: function requires argument type to outlive `'2`
-  --> tests/compile/scope_callback_inner.rs:7:17
-   |
-7  |           let f = scope
-   |  _________________^
-8  | |             .create_function_mut(|_, t: Table| {
-9  | |                 inner = Some(t);
-10 | |                 Ok(())
-11 | |             })?;
-   | |______________^
-help: to force the closure to take ownership of `inner` (and any other referenced variables), use the `move` keyword
-   |
-8  |             .create_function_mut(move |_, t: Table| {
-   |                                  ++++
+error[E0599]: no method named `scope` found for struct `Lua` in the current scope
+ --> tests/compile/scope_callback_inner.rs:5:9
+  |
+5 |     lua.scope(|scope| {
+  |     ----^^^^^ method not found in `Lua`

tests/compile/scope_callback_outer.rs

@@ -9,7 +9,7 @@ fn main() {
                 outer = Some(t);
                 Ok(())
             })?;
-        f.call::<_, ()>(lua.create_table()?)?;
+        f.call::<()>(lua.create_table()?)?;
         Ok(())
     });
 }

tests/compile/scope_callback_outer.stderr

@@ -1,30 +1,5 @@
-error[E0521]: borrowed data escapes outside of closure
-  --> $DIR/scope_callback_outer.rs:7:17
-   |
-6  |       lua.scope(|scope| {
-   |                  -----
-   |                  |
-   |                  `scope` declared here, outside of the closure body
-   |                  `scope` is a reference that is only valid in the closure body
-7  |           let f = scope
-   |  _________________^
-8  | |             .create_function_mut(|_, t: Table| {
-9  | |                 outer = Some(t);
-10 | |                 Ok(())
-11 | |             })?;
-   | |______________^ `scope` escapes the closure body here
-
-error[E0597]: `outer` does not live long enough
-  --> $DIR/scope_callback_outer.rs:9:17
-   |
-6  |     lua.scope(|scope| {
-   |               ------- value captured here
-...
-9  |                 outer = Some(t);
-   |                 ^^^^^ borrowed value does not live long enough
-...
-15 | }
-   | -
-   | |
-   | `outer` dropped here while still borrowed
-   | borrow might be used here, when `outer` is dropped and runs the destructor for type `Option<LuaTable<'_>>`
+error[E0599]: no method named `scope` found for struct `Lua` in the current scope
+ --> tests/compile/scope_callback_outer.rs:6:9
+  |
+6 |     lua.scope(|scope| {
+  |     ----^^^^^ method not found in `Lua`

tests/compile/scope_invariance.rs

@@ -18,6 +18,6 @@ fn main() {
                 })?
         };
 
-        f.call::<_, ()>(())
+        f.call::<()>(())
     });
 }

tests/compile/scope_invariance.stderr

@@ -1,25 +1,5 @@
-error[E0373]: closure may outlive the current function, but it borrows `test.field`, which is owned by the current function
-  --> tests/compile/scope_invariance.rs:14:38
-   |
-9  |     lua.scope(|scope| {
-   |                ----- has type `&mlua::Scope<'_, '1>`
-...
-14 |                 .create_function_mut(|_, ()| {
-   |                                      ^^^^^^^ may outlive borrowed value `test.field`
-15 |                     test.field = 42;
-   |                     ---------- `test.field` is borrowed here
-   |
-note: function requires argument type to outlive `'1`
-  --> tests/compile/scope_invariance.rs:13:13
-   |
-13 | /             scope
-14 | |                 .create_function_mut(|_, ()| {
-15 | |                     test.field = 42;
-16 | |                     //~^ error: `test` does not live long enough
-17 | |                     Ok(())
-18 | |                 })?
-   | |__________________^
-help: to force the closure to take ownership of `test.field` (and any other referenced variables), use the `move` keyword
-   |
-14 |                 .create_function_mut(move |_, ()| {
-   |                                      ++++
+error[E0599]: no method named `scope` found for struct `Lua` in the current scope
+ --> tests/compile/scope_invariance.rs:9:9
+  |
+9 |     lua.scope(|scope| {
+  |     ----^^^^^ method not found in `Lua`