Update CHANGELOG for v0.10.0-beta.1

Make borrowing using new `BorrowedStr` and `BorrowedBytes` types that holds strong reference to Lua.

.github/workflows/main.yml

@@ -27,7 +27,7 @@ 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,send,serialize,macros,unstable"
         shell: bash
       - name: Build ${{ matrix.lua }} pkg-config
         if: ${{ matrix.os == 'ubuntu-22.04' }}
@@ -50,7 +50,7 @@ jobs:
           toolchain: stable
           target: aarch64-apple-darwin
       - name: Cross-compile
-        run: cargo build --target aarch64-apple-darwin --features "${{ 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,unstable"
 
   build_aarch64_cross_ubuntu:
     name: Cross-compile to aarch64-unknown-linux-gnu
@@ -71,7 +71,7 @@ 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,unstable"
         shell: bash
 
   build_armv7_cross_ubuntu:
@@ -93,7 +93,7 @@ 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,unstable"
         shell: bash
 
   test:
@@ -122,14 +122,14 @@ 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 "${{ matrix.lua }},vendored,async,send,serialize,macros"
+          cargo test --features "${{ matrix.lua }},vendored,async,serialize,macros,unstable"
         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,unstable" -- --ignored
         shell: bash
 
   test_with_sanitizer:
@@ -153,7 +153,7 @@ 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,send,serialize,macros,unstable" --target x86_64-unknown-linux-gnu -- --skip test_too_many_recursions
         shell: bash
         env:
           RUSTFLAGS: -Z sanitizer=address
@@ -226,17 +226,16 @@ 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 "${{ matrix.lua }},vendored,async,send,serialize,macros"
+          cargo test --tests --features "${{ matrix.lua }},vendored,async,serialize,macros,unstable"
 
   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 +254,4 @@ 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,unstable"

CHANGELOG.md

@@ -1,3 +1,12 @@
+## 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

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mlua"
-version = "0.9.9" # remember to update mlua_derive
+version = "0.10.0-beta.1" # remember to update mlua_derive
 authors = ["Aleksandr Orlenko <zxteam@pm.me>", "kyren <catherine@kyju.org>"]
 rust-version = "1.71"
 edition = "2021"
@@ -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", "unstable"]
 rustdoc-args = ["--cfg", "docsrs"]
 
 [workspace]
@@ -46,14 +46,13 @@ unstable = []
 [dependencies]
 mlua_derive = { version = "=0.9.3", optional = true, path = "mlua_derive" }
 bstr = { version = "1.0", features = ["std"], default-features = false }
-once_cell = { version = "1.0" }
 num-traits = { version = "0.2.14" }
 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 = "0.6.1", path = "mlua-sys" }
 
@@ -62,7 +61,6 @@ libloading = { version = "0.8", optional = true }
 
 [dev-dependencies]
 trybuild = "1.0"
-futures = "0.3.5"
 hyper = { version = "1.2", features = ["full"] }
 hyper-util = { version = "0.1.3", features = ["full"] }
 http-body-util = "0.1.1"
@@ -102,11 +100,11 @@ 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

@@ -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/main/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.

benches/benchmark.rs

@@ -183,9 +183,7 @@ 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()?))
-        })
+        .create_function(|_, (a, b): (LuaString, LuaString)| Ok(format!("{}{}", a.to_str()?, b.to_str()?)))
         .unwrap();
     let i = AtomicUsize::new(0);
 
@@ -305,7 +303,7 @@ fn userdata_create(c: &mut Criterion) {
 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) {
+        fn add_methods<'a, M: LuaUserDataMethods<'a, Self>>(methods: &mut M) {
             methods.add_meta_method(LuaMetaMethod::Index, move |_, _, key: LuaString| Ok(key));
         }
     }
@@ -331,7 +329,7 @@ fn userdata_call_index(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) {
+        fn add_methods<'a, M: LuaUserDataMethods<'a, Self>>(methods: &mut M) {
             methods.add_method("add", |_, this, i: i64| Ok(this.0 + i));
         }
     }
@@ -361,7 +359,7 @@ fn userdata_call_method(c: &mut Criterion) {
 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) {
+        fn add_methods<'a, M: LuaUserDataMethods<'a, Self>>(methods: &mut M) {
             methods.add_async_method("add", |_, this, i: i64| async move {
                 task::yield_now().await;
                 Ok(this.0 + i)
@@ -383,17 +381,10 @@ fn userdata_async_call_method(c: &mut Criterion) {
         b.to_async(rt).iter_batched(
             || {
                 collect_gc_twice(&lua);
-                (
-                    method.clone(),
-                    ud.clone(),
-                    i.fetch_add(1, Ordering::Relaxed),
-                )
+                (method.clone(), ud.clone(), i.fetch_add(1, Ordering::Relaxed))
             },
             |(method, ud, i)| async move {
-                assert_eq!(
-                    method.call_async::<_, usize>((ud, i)).await.unwrap(),
-                    123 + i
-                );
+                assert_eq!(method.call_async::<_, usize>((ud, i)).await.unwrap(), 123 + i);
             },
             BatchSize::SmallInput,
         );

examples/async_http_server.rs

@@ -1,21 +1,17 @@
 use std::convert::Infallible;
 use std::future::Future;
 use std::net::SocketAddr;
-use std::rc::Rc;
+use std::pin::Pin;
 
-use futures::future::LocalBoxFuture;
-use http_body_util::{combinators::BoxBody, BodyExt as _, Empty, Full};
+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 hyper_util::server::conn::auto::Builder as ServerConnBuilder;
 use tokio::net::TcpListener;
-use tokio::task::LocalSet;
 
-use mlua::{
-    chunk, Error as LuaError, Function, Lua, RegistryKey, String as LuaString, Table, UserData,
-    UserDataMethods,
-};
+use mlua::{chunk, Error as LuaError, Function, Lua, String as LuaString, Table, UserData, UserDataMethods};
 
 /// Wrapper around incoming request that implements UserData
 struct LuaRequest(SocketAddr, Request<Incoming>);
@@ -31,33 +27,26 @@ impl UserData for LuaRequest {
 /// Service that handles incoming requests
 #[derive(Clone)]
 pub struct Svc {
-    lua: Rc<Lua>,
-    handler: Rc<RegistryKey>,
+    handler: Function,
     peer_addr: SocketAddr,
 }
 
 impl Svc {
-    pub fn new(lua: Rc<Lua>, handler: Rc<RegistryKey>, peer_addr: SocketAddr) -> Self {
-        Self {
-            lua,
-            handler,
-            peer_addr,
-        }
+    pub fn new(handler: Function, peer_addr: SocketAddr) -> Self {
+        Self { handler, peer_addr }
     }
 }
 
 impl hyper::service::Service<Request<Incoming>> for Svc {
     type Response = Response<BoxBody<Bytes, Infallible>>;
     type Error = LuaError;
-    type Future = LocalBoxFuture<'static, Result<Self::Response, Self::Error>>;
+    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.lua.clone();
-        let handler_key = self.handler.clone();
+        let handler = self.handler.clone();
         let lua_req = LuaRequest(self.peer_addr, req);
         Box::pin(async move {
-            let handler: Function = lua.registry_value(&handler_key)?;
             match handler.call_async::<_, Table>(lua_req).await {
                 Ok(lua_resp) => {
                     let status = lua_resp.get::<_, Option<u16>>("status")?.unwrap_or(200);
@@ -67,14 +56,14 @@ impl hyper::service::Service<Request<Incoming>> for Svc {
                     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| Full::new(Bytes::copy_from_slice(b.as_bytes())).boxed())
+                        .map(|b| Full::new(Bytes::copy_from_slice(&b.as_bytes())).boxed())
                         .unwrap_or_else(|| Empty::<Bytes>::new().boxed());
 
                     Ok(resp.body(body).unwrap())
@@ -93,10 +82,10 @@ impl hyper::service::Service<Request<Incoming>> 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: RegistryKey = lua
+    let handler = lua
         .load(chunk! {
             function(req)
                 return {
@@ -110,15 +99,13 @@ async fn main() {
                 }
             end
         })
-        .eval()
+        .eval::<Function>()
         .expect("Failed to create Lua handler");
-    let handler = Rc::new(handler);
 
     let listen_addr = "127.0.0.1:3000";
     let listener = TcpListener::bind(listen_addr).await.unwrap();
     println!("Listening on http://{listen_addr}");
 
-    let local = LocalSet::new();
     loop {
         let (stream, peer_addr) = match listener.accept().await {
             Ok(x) => x,
@@ -128,29 +115,14 @@ async fn main() {
             }
         };
 
-        let svc = Svc::new(lua.clone(), handler.clone(), peer_addr);
-        local
-            .run_until(async move {
-                let result = ServerConnBuilder::new(LocalExec)
-                    .http1()
-                    .serve_connection(TokioIo::new(stream), svc)
-                    .await;
-                if let Err(err) = result {
-                    eprintln!("Error serving connection: {err:?}");
-                }
-            })
-            .await;
-    }
-}
-
-#[derive(Clone, Copy, Debug)]
-struct LocalExec;
-
-impl<F> hyper::rt::Executor<F> for LocalExec
-where
-    F: 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

@@ -1,20 +1,16 @@
 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, Function, Lua, String as LuaString, 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())
-        });
+        methods.add_method("peer_addr", |_, this, ()| Ok(this.0.peer_addr()?.to_string()));
 
         methods.add_async_method_mut("read", |lua, this, size| async move {
             let mut buf = vec![0; size];
@@ -35,14 +31,12 @@ impl UserData for LuaTcpStream {
     }
 }
 
-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,
@@ -50,13 +44,8 @@ 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 {
                 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
@@ -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!(),
@@ -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())?;

mlua-sys/src/lib.rs

@@ -54,10 +54,7 @@ pub const LUA_TRACEBACK_STACK: c_int = 11;
     target_arch = "sparc",
     target_arch = "wasm32",
     target_arch = "hexagon",
-    all(
-        target_arch = "riscv32",
-        not(any(target_os = "espidf", target_os = "zkvm"))
-    ),
+    all(target_arch = "riscv32", not(any(target_os = "espidf", target_os = "zkvm"))),
     all(target_arch = "xtensa", not(target_os = "espidf")),
 ))]
 #[doc(hidden)]

mlua-sys/src/lua51/compat.rs

@@ -2,9 +2,8 @@
 //!
 //! Based on github.com/keplerproject/lua-compat-5.3
 
-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::*;
@@ -328,12 +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)
 }
 
@@ -365,12 +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);
@@ -446,12 +435,7 @@ 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);
@@ -543,12 +527,7 @@ 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

@@ -379,12 +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

@@ -157,22 +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);
@@ -240,12 +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 {

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;
@@ -471,12 +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

@@ -5,12 +5,7 @@ use std::os::raw::c_int;
 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);

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)]

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);
 }
 
 //
@@ -175,12 +165,7 @@ 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/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;
 }

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);
@@ -345,18 +335,10 @@ 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;
         }
     }
@@ -397,12 +379,7 @@ 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 +471,7 @@ 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 {

mlua-sys/src/luau/lua.rs

@@ -84,12 +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> {
@@ -426,12 +422,7 @@ pub unsafe fn lua_pushcclosure(L: *mut lua_State, f: lua_CFunction, nup: c_int)
 }
 
 #[inline(always)]
-pub unsafe fn lua_pushcclosured(
-    L: *mut lua_State,
-    f: lua_CFunction,
-    debugname: *const c_char,
-    nup: c_int,
-) {
+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)
 }
 
@@ -476,12 +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;
@@ -489,19 +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;
 }

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/src/from_lua.rs

@@ -3,9 +3,7 @@ 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();
@@ -15,9 +13,9 @@ pub fn from_lua(input: TokenStream) -> TokenStream {
     };
 
     quote! {
-      impl #impl_generics ::mlua::FromLua<'_> for #ident #ty_generics #where_clause {
+      impl #impl_generics ::mlua::FromLua for #ident #ty_generics #where_clause {
         #[inline]
-        fn from_lua(value: ::mlua::Value<'_>, _: &'_ ::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

@@ -99,15 +99,14 @@ pub fn chunk(input: TokenStream) -> TokenStream {
         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);
@@ -125,9 +124,7 @@ 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()?;
@@ -139,9 +136,9 @@ 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

@@ -1,8 +1,6 @@
-use std::{
-    cmp::{Eq, PartialEq},
-    fmt::{self, Display, Formatter},
-    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;
@@ -47,10 +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)> {
@@ -79,9 +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

@@ -7,7 +7,7 @@ use std::string::String as StdString;
 
 use crate::error::{Error, ErrorContext, Result};
 use crate::function::Function;
-use crate::lua::Lua;
+use crate::state::{Lua, WeakLua};
 use crate::table::Table;
 use crate::value::{FromLuaMulti, IntoLua, IntoLuaMulti};
 
@@ -15,7 +15,7 @@ use crate::value::{FromLuaMulti, IntoLua, IntoLuaMulti};
 ///
 /// [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")]
@@ -290,7 +290,7 @@ impl Compiler {
     }
 }
 
-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();
@@ -299,8 +299,8 @@ 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.
@@ -308,10 +308,12 @@ 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 {
+    pub fn set_environment<V: IntoLua>(mut self, env: V) -> Self {
+        let lua = self.lua.lock();
+        let lua = lua.lua();
         self.env = env
-            .into_lua(self.lua)
-            .and_then(|val| self.lua.unpack(val))
+            .into_lua(lua)
+            .and_then(|val| lua.unpack(val))
             .context("bad environment value");
         self
     }
@@ -363,7 +365,7 @@ 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
@@ -388,7 +390,7 @@ 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
@@ -402,7 +404,7 @@ 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<A: IntoLuaMulti, R: FromLuaMulti>(self, args: A) -> Result<R> {
         self.into_function()?.call(args)
     }
 
@@ -417,8 +419,8 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
     #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
     pub async fn call_async<A, R>(self, args: A) -> Result<R>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua,
+        A: IntoLuaMulti,
+        R: FromLuaMulti,
     {
         self.into_function()?.call_async(args).await
     }
@@ -427,7 +429,7 @@ 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
@@ -436,6 +438,7 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
 
         let name = Self::convert_name(self.name)?;
         self.lua
+            .lock()
             .load_chunk(Some(&name), self.env?, self.mode, self.source?.as_ref())
     }
 
@@ -447,15 +450,12 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
             if self.detect_mode() == ChunkMode::Text {
                 #[cfg(feature = "luau")]
                 {
-                    let data = self
-                        .compiler
-                        .get_or_insert_with(Default::default)
-                        .compile(source);
+                    let 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);
@@ -474,7 +474,8 @@ 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);
@@ -490,13 +491,14 @@ 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);
+                    };
                 }
             }
         }
@@ -504,7 +506,7 @@ 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)?;
@@ -519,6 +521,7 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
 
         let name = Self::convert_name(self.name.clone())?;
         self.lua
+            .lock()
             .load_chunk(Some(&name), self.env.clone()?, None, &source)
     }
 

src/error.rs

@@ -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`.
@@ -122,8 +99,8 @@ impl<'lua> Function<'lua> {
     /// # Ok(())
     /// # }
     /// ```
-    pub fn call<A: IntoLuaMulti<'lua>, R: FromLuaMulti<'lua>>(&self, args: A) -> Result<R> {
-        let lua = self.0.lua;
+    pub fn call<A: IntoLuaMulti, R: FromLuaMulti>(&self, args: A) -> 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 +153,19 @@ 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<A, R>(&self, args: A) -> impl Future<Output = Result<R>>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua,
+        A: IntoLuaMulti,
+        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 }
     }
 
@@ -217,7 +196,7 @@ impl<'lua> Function<'lua> {
     /// # Ok(())
     /// # }
     /// ```
-    pub fn bind<A: IntoLuaMulti<'lua>>(&self, args: A) -> Result<Function<'lua>> {
+    pub fn bind<A: IntoLuaMulti>(&self, args: A) -> 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 +212,10 @@ 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 +231,7 @@ 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 +241,7 @@ impl<'lua> Function<'lua> {
             Function(lua.pop_ref())
         };
 
+        let lua = lua.lua();
         lua.load(
             r#"
             local func, args_wrapper = ...
@@ -272,7 +252,7 @@ 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 +261,7 @@ 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 +298,7 @@ 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 +322,7 @@ 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 +345,7 @@ 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 +406,7 @@ 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 +424,8 @@ 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 +463,7 @@ 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);
@@ -514,134 +495,98 @@ impl<'lua> Function<'lua> {
     #[cfg(feature = "luau")]
     #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
     pub fn deep_clone(&self) -> Self {
-        let ref_thread = self.0.lua.ref_thread();
+        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(self.0.lua.pop_ref_thread())
+            Function(lua.pop_ref_thread())
         }
     }
-
-    /// 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) -> OwnedFunction {
-        OwnedFunction(self.0.into_owned())
-    }
 }
 
-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<'static>);
 
 #[cfg(feature = "async")]
-pub(crate) struct WrappedAsyncFunction<'lua>(pub(crate) AsyncCallback<'lua, 'static>);
+pub(crate) struct WrappedAsyncFunction(pub(crate) AsyncCallback<'static>);
 
-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>> + 'static,
     {
-        WrappedAsyncFunction(Box::new(move |lua, args| unsafe {
+        WrappedAsyncFunction(Box::new(move |rawlua, args| unsafe {
+            let lua = rawlua.lua();
             let args = match A::from_lua_args(args, 1, None, lua) {
                 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 weak = rawlua.weak().clone();
+            Box::pin(async move { fut.await?.push_into_stack_multi(&weak.lock()) })
         }))
     }
 }
 
-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)
     }
 }
 
@@ -649,8 +594,8 @@ 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
@@ -84,20 +84,18 @@ 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 types;
 mod userdata;
-mod userdata_ext;
-mod userdata_impl;
 mod util;
 mod value;
 
@@ -109,20 +107,18 @@ 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::string::{BorrowedBytes, BorrowedStr, String};
 pub use crate::table::{Table, TableExt, TablePairs, TableSequence};
 pub use crate::thread::{Thread, ThreadStatus};
 pub use crate::types::{AppDataRef, AppDataRefMut, Integer, LightUserData, Number, RegistryKey};
 pub use crate::userdata::{
-    AnyUserData, MetaMethod, UserData, UserDataFields, UserDataMetatable, UserDataMethods,
-    UserDataRef, UserDataRefMut,
+    AnyUserData, AnyUserDataExt, 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 +137,7 @@ 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 +148,6 @@ 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 +188,8 @@ 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`.
 ///
@@ -266,7 +253,6 @@ pub use mlua_derive::FromLua;
 ///     ...
 /// }
 /// ```
-///
 #[cfg(any(feature = "module", docsrs))]
 #[cfg_attr(docsrs, doc(cfg(feature = "module")))]
 pub use mlua_derive::lua_module;
@@ -279,6 +265,6 @@ 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

@@ -7,7 +7,7 @@ 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};
@@ -53,7 +53,7 @@ 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)
     let package = lua.create_table()?;
-    lua.set_app_data(PackageKey(lua.create_registry_value(package.clone())?));
+    lua.set_app_data(PackageKey(lua.create_registry_value(&package)?));
 
     // Set `package.path`
     let mut search_path = env::var("LUAU_PATH")
@@ -82,12 +82,12 @@ 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())?;
+    package.raw_set("loaded", &loaded)?;
     lua.set_named_registry_value("_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)?)?;
@@ -225,14 +225,13 @@ fn dylib_loader(lua: &Lua, modname: StdString) -> Result<Value> {
     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

@@ -1,135 +1,104 @@
+use std::iter::FromIterator;
 use std::ops::{Deref, DerefMut};
 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)
     }
 
     #[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> {
         match self {
-            Ok(v) => v.push_into_stack(lua).map(|_| 1),
-            Err(e) => {
-                let state = lua.state();
-                check_stack(state, 3)?;
-                ffi::lua_pushnil(state);
-                e.push_into_stack(lua)?;
-                Ok(2)
-            }
+            Ok(val) => (val,).push_into_stack_multi(lua),
+            Err(err) => (Nil, err).push_into_stack_multi(lua),
         }
     }
 }
 
-impl<'lua, E: IntoLua<'lua>> IntoLuaMulti<'lua> for StdResult<(), E> {
+impl<E: IntoLua> IntoLuaMulti for StdResult<(), E> {
     #[inline]
-    fn into_lua_multi(self, lua: &'lua Lua) -> Result<MultiValue<'lua>> {
+    fn into_lua_multi(self, lua: &Lua) -> Result<MultiValue> {
         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(_) => Ok(MultiValue::new()),
+            Err(err) => (Nil, err).into_lua_multi(lua),
         }
     }
 
     #[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> {
         match self {
             Ok(_) => Ok(0),
-            Err(e) => {
-                let state = lua.state();
-                check_stack(state, 3)?;
-                ffi::lua_pushnil(state);
-                e.push_into_stack(lua)?;
-                Ok(2)
-            }
+            Err(err) => (Nil, err).push_into_stack_multi(lua),
         }
     }
 }
 
-impl<'lua, T: IntoLua<'lua>> IntoLuaMulti<'lua> for T {
+impl<T: IntoLua> IntoLuaMulti for T {
     #[inline]
-    fn into_lua_multi(self, lua: &'lua Lua) -> Result<MultiValue<'lua>> {
+    fn into_lua_multi(self, lua: &Lua) -> Result<MultiValue> {
         let mut v = MultiValue::with_lua_and_capacity(lua, 1);
-        v.push_front(self.into_lua(lua)?);
+        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)
     }
 }
@@ -205,21 +174,21 @@ 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>> {
+    fn into_lua_multi(self, lua: &Lua) -> Result<MultiValue> {
         let mut values = MultiValue::with_lua_and_capacity(lua, self.0.len());
-        values.refill(self.0.into_iter().map(|e| e.into_lua(lua)))?;
+        values.extend_from_values(self.0.into_iter().map(|val| val.into_lua(lua)))?;
         Ok(values)
     }
 }
 
-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)
     }
@@ -227,26 +196,26 @@ 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>> {
+            fn into_lua_multi(self, lua: &Lua) -> Result<MultiValue> {
                 Ok(MultiValue::with_lua_and_capacity(lua, 0))
             }
 
             #[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);
                 }
@@ -256,13 +225,13 @@ 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)?;
@@ -272,7 +241,7 @@ 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;
                 $(
@@ -288,13 +257,13 @@ 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,))
@@ -302,7 +271,7 @@ 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;
@@ -313,13 +282,13 @@ 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)?;
@@ -328,13 +297,13 @@ 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,
+    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,
+    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,
 };
@@ -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);
@@ -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

@@ -14,8 +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>>>,
 }
@@ -93,14 +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,
@@ -108,11 +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,
@@ -121,7 +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]
@@ -139,8 +135,8 @@ impl<'lua, 'de> serde::Deserializer<'de> for Deserializer<'lua> {
             #[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),
@@ -150,8 +146,9 @@ impl<'lua, 'de> serde::Deserializer<'de> for Deserializer<'lua> {
             }
             #[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(ud.0.lua.ref_thread(), ud.0.index, &mut size);
+                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)
@@ -266,10 +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() => {
@@ -291,12 +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>,
     {
@@ -313,7 +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,
@@ -394,13 +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>>
@@ -453,8 +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),
@@ -466,13 +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
@@ -497,8 +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 {
@@ -508,15 +496,15 @@ 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> {
+impl<'de> de::MapAccess<'de> for MapDeserializer<'_> {
     type Error = Error;
 
     fn next_key_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>>
@@ -566,16 +554,16 @@ 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
@@ -591,13 +579,13 @@ 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<()> {
@@ -615,9 +603,7 @@ 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",

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

@@ -2,14 +2,14 @@ use serde::{ser, Serialize};
 
 use super::LuaSerdeExt;
 use crate::error::{Error, Result};
-use crate::lua::Lua;
+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,
 }
 
@@ -96,8 +96,8 @@ impl Options {
 
     /// 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 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.
     ///
@@ -109,14 +109,14 @@ impl Options {
     }
 }
 
-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 }
     }
 }
@@ -124,28 +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 = SerializeStruct<'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))
     }
 
@@ -164,22 +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 {
@@ -188,7 +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,
     {
@@ -196,7 +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 {
@@ -205,7 +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 {
@@ -219,12 +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,
     {
@@ -238,7 +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,
     {
@@ -255,7 +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]
@@ -264,11 +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));
@@ -286,6 +282,7 @@ impl<'lua> ser::Serializer for Serializer<'lua> {
         _len: usize,
     ) -> Result<Self::SerializeTupleVariant> {
         Ok(SerializeTupleVariant {
+            lua: self.lua,
             variant,
             table: self.lua.create_table()?,
             options: self.options,
@@ -295,6 +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,
@@ -330,6 +328,7 @@ impl<'lua> ser::Serializer for Serializer<'lua> {
         len: usize,
     ) -> Result<Self::SerializeStructVariant> {
         Ok(SerializeStructVariant {
+            lua: self.lua,
             variant,
             table: self.lua.create_table_with_capacity(0, len)?,
             options: self.options,
@@ -338,19 +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),
@@ -360,7 +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()),
@@ -371,8 +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<()>
@@ -386,13 +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<()>
@@ -402,13 +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<()>
@@ -426,7 +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));
@@ -436,49 +435,48 @@ impl<'lua> ser::SerializeTupleStruct for SerializeSeq<'lua> {
 }
 
 #[doc(hidden)]
-pub struct SerializeTupleVariant<'lua> {
+pub struct SerializeTupleVariant<'a> {
+    lua: &'a Lua,
     variant: &'static str,
-    table: Table<'lua>,
+    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()?;
+    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(())
     }
 
@@ -486,29 +484,25 @@ 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))
     }
 }
 
 #[doc(hidden)]
-pub struct SerializeStruct<'lua> {
-    lua: &'lua Lua,
-    inner: Option<Value<'lua>>,
+pub struct SerializeStruct<'a> {
+    lua: &'a Lua,
+    inner: Option<Value>,
     options: Options,
 }
 
-impl<'lua> ser::SerializeStruct for SerializeStruct<'lua> {
-    type Ok = Value<'lua>;
+impl ser::SerializeStruct for SerializeStruct<'_> {
+    type Ok = Value;
     type Error = Error;
 
     fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<()>
@@ -529,7 +523,7 @@ impl<'lua> ser::SerializeStruct for SerializeStruct<'lua> {
         Ok(())
     }
 
-    fn end(self) -> Result<Value<'lua>> {
+    fn end(self) -> Result<Value> {
         match self.inner {
             Some(table @ Value::Table(_)) => Ok(table),
             Some(value) if self.options.detect_serde_json_arbitrary_precision => {
@@ -551,29 +545,28 @@ impl<'lua> ser::SerializeStruct for SerializeStruct<'lua> {
 }
 
 #[doc(hidden)]
-pub struct SerializeStructVariant<'lua> {
+pub struct SerializeStructVariant<'a> {
+    lua: &'a Lua,
     variant: &'static str,
-    table: Table<'lua>,
+    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_with_capacity(0, 1)?;
+    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 +1,247 @@
+use std::any::TypeId;
+use std::cell::UnsafeCell;
+use std::rc::Rc;
+// use std::collections::VecDeque;
+use std::mem::{self, MaybeUninit};
+use std::os::raw::{c_int, c_void};
+use std::ptr;
+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, XWeak};
+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 MULTIVALUE_POOL_SIZE: usize = 64;
+const REF_STACK_RESERVE: c_int = 1;
+
+/// Data associated with the Lua state.
+pub(crate) struct ExtraData {
+    // Same layout as `Lua`
+    pub(super) lua: MaybeUninit<XRc<ReentrantMutex<RawLua>>>,
+    // Same layout as `WeakLua`
+    pub(super) weak: MaybeUninit<XWeak<ReentrantMutex<RawLua>>>,
+
+    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,
+    #[cfg(feature = "module")]
+    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 `MultiValue` containers
+    // multivalue_pool: Vec<VecDeque<Value>>,
+    // 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 {
+            #[cfg(feature = "module")]
+            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) -> 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);
+        }
+
+        let extra = XRc::new(UnsafeCell::new(ExtraData {
+            lua: MaybeUninit::uninit(),
+            weak: MaybeUninit::uninit(),
+            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,
+            #[cfg(feature = "module")]
+            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),
+            // multivalue_pool: Vec::with_capacity(MULTIVALUE_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, lua: &XRc<ReentrantMutex<RawLua>>) {
+        self.lua.write(XRc::clone(lua));
+        if cfg!(not(feature = "module")) {
+            XRc::decrement_strong_count(XRc::as_ptr(lua));
+        }
+        self.weak.write(XRc::downgrade(lua));
+    }
+
+    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 {
+        mem::transmute(self.lua.assume_init_ref())
+    }
+
+    #[inline(always)]
+    pub(super) unsafe fn raw_lua(&self) -> &RawLua {
+        &*self.lua.assume_init_ref().data_ptr()
+    }
+
+    #[inline(always)]
+    pub(super) unsafe fn weak(&self) -> &WeakLua {
+        mem::transmute(self.weak.assume_init_ref())
+    }
+}

src/state/util.rs

@@ -0,0 +1,181 @@
+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;
+// const MULTIVALUE_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(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(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

@@ -8,12 +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::LuaGuard;
+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 +92,20 @@ 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], LuaGuard) {
+        let lua = self.0.lua.lock();
+        let ref_thread = lua.ref_thread();
         unsafe {
             mlua_debug_assert!(
                 ffi::lua_type(ref_thread, self.0.index) == ffi::LUA_TSTRING,
@@ -128,7 +117,7 @@ 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)
+            (slice::from_raw_parts(data as *const u8, size + 1), lua)
         }
     }
 
@@ -141,21 +130,13 @@ 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 +161,14 @@ 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 +177,151 @@ 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)] LuaGuard);
 
-    /// 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)] LuaGuard);
+
+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.into_iter()
     }
 }
 
@@ -265,5 +329,8 @@ 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);
 }

src/table.rs

@@ -13,39 +13,19 @@ use {
 use crate::error::{Error, Result};
 use crate::function::Function;
 use crate::private::Sealed;
-use crate::types::{Integer, LuaRef};
+use crate::state::{LuaGuard, RawLua};
+use crate::types::{Integer, ValueRef};
 use crate::util::{assert_stack, check_stack, StackGuard};
 use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, Nil, Value};
 
 #[cfg(feature = "async")]
-use futures_util::future::{self, LocalBoxFuture};
+use std::future::Future;
 
 /// Handle to an internal Lua table.
 #[derive(Clone)]
-pub struct Table<'lua>(pub(crate) LuaRef<'lua>);
+pub struct Table(pub(crate) ValueRef);
 
-/// Owned handle to an internal Lua table.
-///
-/// 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 OwnedTable(pub(crate) crate::types::LuaOwnedRef);
-
-#[cfg(feature = "unstable")]
-impl OwnedTable {
-    /// Get borrowed handle to the underlying Lua table.
-    #[cfg_attr(feature = "send", allow(unused))]
-    pub const fn to_ref(&self) -> Table {
-        Table(self.0.to_ref())
-    }
-}
-
-impl<'lua> Table<'lua> {
+impl Table {
     /// Sets a key-value pair in the table.
     ///
     /// If the value is `nil`, this will effectively remove the pair.
@@ -79,21 +59,21 @@ impl<'lua> Table<'lua> {
     /// ```
     ///
     /// [`raw_set`]: #method.raw_set
-    pub fn set<K: IntoLua<'lua>, V: IntoLua<'lua>>(&self, key: K, value: V) -> Result<()> {
+    pub fn set<K: IntoLua, V: IntoLua>(&self, key: K, value: V) -> Result<()> {
         // Fast track
         if !self.has_metatable() {
             return self.raw_set(key, value);
         }
 
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
             check_stack(state, 5)?;
 
             lua.push_ref(&self.0);
-            key.push_into_stack(lua)?;
-            value.push_into_stack(lua)?;
+            key.push_into_stack(&lua)?;
+            value.push_into_stack(&lua)?;
             protect_lua!(state, 3, 0, fn(state) ffi::lua_settable(state, -3))
         }
     }
@@ -122,50 +102,50 @@ impl<'lua> Table<'lua> {
     /// ```
     ///
     /// [`raw_get`]: #method.raw_get
-    pub fn get<K: IntoLua<'lua>, V: FromLua<'lua>>(&self, key: K) -> Result<V> {
+    pub fn get<K: IntoLua, V: FromLua>(&self, key: K) -> Result<V> {
         // Fast track
         if !self.has_metatable() {
             return self.raw_get(key);
         }
 
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
             check_stack(state, 4)?;
 
             lua.push_ref(&self.0);
-            key.push_into_stack(lua)?;
+            key.push_into_stack(&lua)?;
             protect_lua!(state, 2, 1, fn(state) ffi::lua_gettable(state, -2))?;
 
-            V::from_stack(-1, lua)
+            V::from_stack(-1, &lua)
         }
     }
 
     /// Checks whether the table contains a non-nil value for `key`.
     ///
     /// This might invoke the `__index` metamethod.
-    pub fn contains_key<K: IntoLua<'lua>>(&self, key: K) -> Result<bool> {
+    pub fn contains_key<K: IntoLua>(&self, key: K) -> Result<bool> {
         Ok(self.get::<_, Value>(key)? != Value::Nil)
     }
 
     /// Appends a value to the back of the table.
     ///
     /// This might invoke the `__len` and `__newindex` metamethods.
-    pub fn push<V: IntoLua<'lua>>(&self, value: V) -> Result<()> {
+    pub fn push<V: IntoLua>(&self, value: V) -> Result<()> {
         // Fast track
         if !self.has_metatable() {
             return self.raw_push(value);
         }
 
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
             check_stack(state, 4)?;
 
             lua.push_ref(&self.0);
-            value.push_into_stack(lua)?;
+            value.push_into_stack(&lua)?;
             protect_lua!(state, 2, 0, fn(state) {
                 let len = ffi::luaL_len(state, -2) as Integer;
                 ffi::lua_seti(state, -2, len + 1);
@@ -177,13 +157,13 @@ impl<'lua> Table<'lua> {
     /// Removes the last element from the table and returns it.
     ///
     /// This might invoke the `__len` and `__newindex` metamethods.
-    pub fn pop<V: FromLua<'lua>>(&self) -> Result<V> {
+    pub fn pop<V: FromLua>(&self) -> Result<V> {
         // Fast track
         if !self.has_metatable() {
             return self.raw_pop();
         }
 
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
@@ -196,7 +176,7 @@ impl<'lua> Table<'lua> {
                 ffi::lua_pushnil(state);
                 ffi::lua_seti(state, -3, len);
             })?;
-            V::from_stack(-1, lua)
+            V::from_stack(-1, &lua)
         }
     }
 
@@ -240,16 +220,12 @@ impl<'lua> Table<'lua> {
         // If self does not define it, then check the other table.
         if let Some(mt) = self.get_metatable() {
             if mt.contains_key("__eq")? {
-                return mt
-                    .get::<_, Function>("__eq")?
-                    .call((self.clone(), other.clone()));
+                return mt.get::<_, Function>("__eq")?.call((self, other));
             }
         }
         if let Some(mt) = other.get_metatable() {
             if mt.contains_key("__eq")? {
-                return mt
-                    .get::<_, Function>("__eq")?
-                    .call((self.clone(), other.clone()));
+                return mt.get::<_, Function>("__eq")?.call((self, other));
             }
         }
 
@@ -257,19 +233,19 @@ impl<'lua> Table<'lua> {
     }
 
     /// Sets a key-value pair without invoking metamethods.
-    pub fn raw_set<K: IntoLua<'lua>, V: IntoLua<'lua>>(&self, key: K, value: V) -> Result<()> {
+    pub fn raw_set<K: IntoLua, V: IntoLua>(&self, key: K, value: V) -> Result<()> {
         #[cfg(feature = "luau")]
         self.check_readonly_write()?;
 
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
             check_stack(state, 5)?;
 
             lua.push_ref(&self.0);
-            key.push_into_stack(lua)?;
-            value.push_into_stack(lua)?;
+            key.push_into_stack(&lua)?;
+            value.push_into_stack(&lua)?;
 
             if lua.unlikely_memory_error() {
                 ffi::lua_rawset(state, -3);
@@ -282,37 +258,37 @@ impl<'lua> Table<'lua> {
     }
 
     /// Gets the value associated to `key` without invoking metamethods.
-    pub fn raw_get<K: IntoLua<'lua>, V: FromLua<'lua>>(&self, key: K) -> Result<V> {
-        let lua = self.0.lua;
+    pub fn raw_get<K: IntoLua, V: FromLua>(&self, key: K) -> Result<V> {
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
             check_stack(state, 3)?;
 
             lua.push_ref(&self.0);
-            key.push_into_stack(lua)?;
+            key.push_into_stack(&lua)?;
             ffi::lua_rawget(state, -2);
 
-            V::from_stack(-1, lua)
+            V::from_stack(-1, &lua)
         }
     }
 
-    /// Inserts element value at position `idx` to the table, shifting up the elements from `table[idx]`.
-    /// The worst case complexity is O(n), where n is the table length.
-    pub fn raw_insert<V: IntoLua<'lua>>(&self, idx: Integer, value: V) -> Result<()> {
+    /// Inserts element value at position `idx` to the table, shifting up the elements from
+    /// `table[idx]`. The worst case complexity is O(n), where n is the table length.
+    pub fn raw_insert<V: IntoLua>(&self, idx: Integer, value: V) -> Result<()> {
         let size = self.raw_len() as Integer;
         if idx < 1 || idx > size + 1 {
             return Err(Error::runtime("index out of bounds"));
         }
 
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
             check_stack(state, 5)?;
 
             lua.push_ref(&self.0);
-            value.push_into_stack(lua)?;
+            value.push_into_stack(&lua)?;
             protect_lua!(state, 2, 0, |state| {
                 for i in (idx..=size).rev() {
                     // table[i+1] = table[i]
@@ -325,18 +301,18 @@ impl<'lua> Table<'lua> {
     }
 
     /// Appends a value to the back of the table without invoking metamethods.
-    pub fn raw_push<V: IntoLua<'lua>>(&self, value: V) -> Result<()> {
+    pub fn raw_push<V: IntoLua>(&self, value: V) -> Result<()> {
         #[cfg(feature = "luau")]
         self.check_readonly_write()?;
 
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
             check_stack(state, 4)?;
 
             lua.push_ref(&self.0);
-            value.push_into_stack(lua)?;
+            value.push_into_stack(&lua)?;
 
             unsafe fn callback(state: *mut ffi::lua_State) {
                 let len = ffi::lua_rawlen(state, -2) as Integer;
@@ -353,11 +329,11 @@ impl<'lua> Table<'lua> {
     }
 
     /// Removes the last element from the table and returns it, without invoking metamethods.
-    pub fn raw_pop<V: FromLua<'lua>>(&self) -> Result<V> {
+    pub fn raw_pop<V: FromLua>(&self) -> Result<V> {
         #[cfg(feature = "luau")]
         self.check_readonly_write()?;
 
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
@@ -370,7 +346,7 @@ impl<'lua> Table<'lua> {
             ffi::lua_pushnil(state);
             ffi::lua_rawseti(state, -3, len);
 
-            V::from_stack(-1, lua)
+            V::from_stack(-1, &lua)
         }
     }
 
@@ -381,10 +357,10 @@ impl<'lua> Table<'lua> {
     /// where n is the table length.
     ///
     /// For other key types this is equivalent to setting `table[key] = nil`.
-    pub fn raw_remove<K: IntoLua<'lua>>(&self, key: K) -> Result<()> {
-        let lua = self.0.lua;
+    pub fn raw_remove<K: IntoLua>(&self, key: K) -> Result<()> {
+        let lua = self.0.lua.lock();
         let state = lua.state();
-        let key = key.into_lua(lua)?;
+        let key = key.into_lua(lua.lua())?;
         match key {
             Value::Integer(idx) => {
                 let size = self.raw_len() as Integer;
@@ -418,7 +394,7 @@ impl<'lua> Table<'lua> {
         #[cfg(feature = "luau")]
         self.check_readonly_write()?;
 
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         unsafe {
             #[cfg(feature = "luau")]
             ffi::lua_cleartable(lua.ref_thread(), self.0.index);
@@ -462,7 +438,7 @@ impl<'lua> Table<'lua> {
             return Ok(self.raw_len() as Integer);
         }
 
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
@@ -475,8 +451,8 @@ impl<'lua> Table<'lua> {
 
     /// Returns the result of the Lua `#` operator, without invoking the `__len` metamethod.
     pub fn raw_len(&self) -> usize {
-        let ref_thread = self.0.lua.ref_thread();
-        unsafe { ffi::lua_rawlen(ref_thread, self.0.index) }
+        let lua = self.0.lua.lock();
+        unsafe { ffi::lua_rawlen(lua.ref_thread(), self.0.index) }
     }
 
     /// Returns `true` if the table is empty, without invoking metamethods.
@@ -489,7 +465,7 @@ impl<'lua> Table<'lua> {
         }
 
         // Check hash part
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
@@ -508,8 +484,8 @@ impl<'lua> Table<'lua> {
     /// Returns a reference to the metatable of this table, or `None` if no metatable is set.
     ///
     /// Unlike the `getmetatable` Lua function, this method ignores the `__metatable` field.
-    pub fn get_metatable(&self) -> Option<Table<'lua>> {
-        let lua = self.0.lua;
+    pub fn get_metatable(&self) -> Option<Table> {
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
@@ -528,14 +504,14 @@ impl<'lua> Table<'lua> {
     ///
     /// If `metatable` is `None`, the metatable is removed (if no metatable is set, this does
     /// nothing).
-    pub fn set_metatable(&self, metatable: Option<Table<'lua>>) {
+    pub fn set_metatable(&self, metatable: Option<Table>) {
         // Workaround to throw readonly error without returning Result
         #[cfg(feature = "luau")]
         if self.is_readonly() {
             panic!("attempt to modify a readonly table");
         }
 
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
@@ -555,7 +531,8 @@ impl<'lua> Table<'lua> {
     #[doc(hidden)]
     #[inline]
     pub fn has_metatable(&self) -> bool {
-        let ref_thread = self.0.lua.ref_thread();
+        let lua = self.0.lua.lock();
+        let ref_thread = lua.ref_thread();
         unsafe {
             if ffi::lua_getmetatable(ref_thread, self.0.index) != 0 {
                 ffi::lua_pop(ref_thread, 1);
@@ -571,7 +548,8 @@ impl<'lua> Table<'lua> {
     #[cfg(any(feature = "luau", doc))]
     #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
     pub fn set_readonly(&self, enabled: bool) {
-        let ref_thread = self.0.lua.ref_thread();
+        let lua = self.0.lua.lock();
+        let ref_thread = lua.ref_thread();
         unsafe {
             ffi::lua_setreadonly(ref_thread, self.0.index, enabled as _);
             if !enabled {
@@ -587,7 +565,8 @@ impl<'lua> Table<'lua> {
     #[cfg(any(feature = "luau", doc))]
     #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
     pub fn is_readonly(&self) -> bool {
-        let ref_thread = self.0.lua.ref_thread();
+        let lua = self.0.lua.lock();
+        let ref_thread = lua.ref_thread();
         unsafe { ffi::lua_getreadonly(ref_thread, self.0.index) != 0 }
     }
 
@@ -602,26 +581,12 @@ impl<'lua> Table<'lua> {
         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) -> OwnedTable {
-        OwnedTable(self.0.into_owned())
-    }
-
-    /// Consume this table and return an iterator over the pairs of the table.
+    /// Returns an iterator over the pairs of the table.
     ///
     /// This works like the Lua `pairs` function, but does not invoke the `__pairs` metamethod.
     ///
     /// The pairs are wrapped in a [`Result`], since they are lazily converted to `K` and `V` types.
     ///
-    /// # Note
-    ///
-    /// While this method consumes the `Table` object, it can not prevent code from mutating the
-    /// table while the iteration is in progress. Refer to the [Lua manual] for information about
-    /// the consequences of such mutation.
-    ///
     /// # Examples
     ///
     /// Iterate over all globals:
@@ -643,9 +608,10 @@ impl<'lua> Table<'lua> {
     ///
     /// [`Result`]: crate::Result
     /// [Lua manual]: http://www.lua.org/manual/5.4/manual.html#pdf-next
-    pub fn pairs<K: FromLua<'lua>, V: FromLua<'lua>>(self) -> TablePairs<'lua, K, V> {
+    pub fn pairs<K: FromLua, V: FromLua>(&self) -> TablePairs<K, V> {
         TablePairs {
-            table: self.0,
+            guard: self.0.lua.lock(),
+            table: self,
             key: Some(Nil),
             _phantom: PhantomData,
         }
@@ -657,10 +623,10 @@ impl<'lua> Table<'lua> {
     /// It does not invoke the `__pairs` metamethod.
     pub fn for_each<K, V>(&self, mut f: impl FnMut(K, V) -> Result<()>) -> Result<()>
     where
-        K: FromLua<'lua>,
-        V: FromLua<'lua>,
+        K: FromLua,
+        V: FromLua,
     {
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
@@ -669,8 +635,8 @@ impl<'lua> Table<'lua> {
             lua.push_ref(&self.0);
             ffi::lua_pushnil(state);
             while ffi::lua_next(state, -2) != 0 {
-                let k = K::from_stack(-2, lua)?;
-                let v = V::from_stack(-1, lua)?;
+                let k = K::from_stack(-2, &lua)?;
+                let v = V::from_stack(-1, &lua)?;
                 f(k, v)?;
                 // Keep key for next iteration
                 ffi::lua_pop(state, 1);
@@ -679,18 +645,12 @@ impl<'lua> Table<'lua> {
         Ok(())
     }
 
-    /// Consume this table and return an iterator over all values in the sequence part of the table.
+    /// Returns an iterator over all values in the sequence part of the table.
     ///
     /// The iterator will yield all values `t[1]`, `t[2]` and so on, until a `nil` value is
     /// encountered. This mirrors the behavior of Lua's `ipairs` function but does not invoke
     /// any metamethods.
     ///
-    /// # Note
-    ///
-    /// While this method consumes the `Table` object, it can not prevent code from mutating the
-    /// table while the iteration is in progress. Refer to the [Lua manual] for information about
-    /// the consequences of such mutation.
-    ///
     /// # Examples
     ///
     /// ```
@@ -717,26 +677,21 @@ impl<'lua> Table<'lua> {
     /// [`pairs`]: #method.pairs
     /// [`Result`]: crate::Result
     /// [Lua manual]: http://www.lua.org/manual/5.4/manual.html#pdf-next
-    pub fn sequence_values<V: FromLua<'lua>>(self) -> TableSequence<'lua, V> {
+    pub fn sequence_values<V: FromLua>(&self) -> TableSequence<V> {
         TableSequence {
-            table: self.0,
+            guard: self.0.lua.lock(),
+            table: self,
             index: 1,
             _phantom: PhantomData,
         }
     }
 
-    #[doc(hidden)]
-    #[deprecated(since = "0.9.0", note = "use `sequence_values` instead")]
-    pub fn raw_sequence_values<V: FromLua<'lua>>(self) -> TableSequence<'lua, V> {
-        self.sequence_values()
-    }
-
     #[cfg(feature = "serialize")]
     pub(crate) fn for_each_value<V>(&self, mut f: impl FnMut(V) -> Result<()>) -> Result<()>
     where
-        V: FromLua<'lua>,
+        V: FromLua,
     {
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
@@ -746,7 +701,7 @@ impl<'lua> Table<'lua> {
             let len = ffi::lua_rawlen(state, -1);
             for i in 1..=len {
                 ffi::lua_rawgeti(state, -1, i as _);
-                f(V::from_stack(-1, lua)?)?;
+                f(V::from_stack(-1, &lua)?)?;
                 ffi::lua_pop(state, 1);
             }
         }
@@ -755,18 +710,18 @@ impl<'lua> Table<'lua> {
 
     /// Sets element value at position `idx` without invoking metamethods.
     #[doc(hidden)]
-    pub fn raw_seti<V: IntoLua<'lua>>(&self, idx: usize, value: V) -> Result<()> {
+    pub fn raw_seti<V: IntoLua>(&self, idx: usize, value: V) -> Result<()> {
         #[cfg(feature = "luau")]
         self.check_readonly_write()?;
 
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
             check_stack(state, 5)?;
 
             lua.push_ref(&self.0);
-            value.push_into_stack(lua)?;
+            value.push_into_stack(&lua)?;
 
             let idx = idx.try_into().unwrap();
             if lua.unlikely_memory_error() {
@@ -780,7 +735,7 @@ impl<'lua> Table<'lua> {
 
     #[cfg(feature = "serialize")]
     pub(crate) fn is_array(&self) -> bool {
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
@@ -812,9 +767,8 @@ impl<'lua> Table<'lua> {
     ) -> fmt::Result {
         visited.insert(self.to_pointer());
 
-        let t = self.clone();
         // Collect key/value pairs into a vector so we can sort them
-        let mut pairs = t.pairs::<Value, Value>().flatten().collect::<Vec<_>>();
+        let mut pairs = self.pairs::<Value, Value>().flatten().collect::<Vec<_>>();
         // Sort keys
         pairs.sort_by(|(a, _), (b, _)| a.cmp(b));
         if pairs.is_empty() {
@@ -832,7 +786,7 @@ impl<'lua> Table<'lua> {
     }
 }
 
-impl fmt::Debug for Table<'_> {
+impl fmt::Debug for Table {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         if fmt.alternate() {
             return self.fmt_pretty(fmt, 0, &mut HashSet::new());
@@ -841,25 +795,25 @@ impl fmt::Debug for Table<'_> {
     }
 }
 
-impl<'lua> PartialEq for Table<'lua> {
+impl PartialEq for Table {
     fn eq(&self, other: &Self) -> bool {
         self.0 == other.0
     }
 }
 
-impl<'lua> AsRef<Table<'lua>> for Table<'lua> {
+impl AsRef<Table> for Table {
     #[inline]
     fn as_ref(&self) -> &Self {
         self
     }
 }
 
-impl<'lua, T> PartialEq<[T]> for Table<'lua>
+impl<T> PartialEq<[T]> for Table
 where
-    T: IntoLua<'lua> + Clone,
+    T: IntoLua + Clone,
 {
     fn eq(&self, other: &[T]) -> bool {
-        let lua = self.0.lua;
+        let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
@@ -874,7 +828,7 @@ where
                 if val == Nil {
                     return i == other.len();
                 }
-                match other.get(i).map(|v| v.clone().into_lua(lua)) {
+                match other.get(i).map(|v| v.clone().into_lua(lua.lua())) {
                     Some(Ok(other_val)) if val == other_val => continue,
                     _ => return false,
                 }
@@ -884,9 +838,9 @@ where
     }
 }
 
-impl<'lua, T> PartialEq<&[T]> for Table<'lua>
+impl<T> PartialEq<&[T]> for Table
 where
-    T: IntoLua<'lua> + Clone,
+    T: IntoLua + Clone,
 {
     #[inline]
     fn eq(&self, other: &&[T]) -> bool {
@@ -894,9 +848,9 @@ where
     }
 }
 
-impl<'lua, T, const N: usize> PartialEq<[T; N]> for Table<'lua>
+impl<T, const N: usize> PartialEq<[T; N]> for Table
 where
-    T: IntoLua<'lua> + Clone,
+    T: IntoLua + Clone,
 {
     #[inline]
     fn eq(&self, other: &[T; N]) -> bool {
@@ -905,24 +859,26 @@ where
 }
 
 /// An extension trait for `Table`s that provides a variety of convenient functionality.
-pub trait TableExt<'lua>: Sealed {
+pub trait TableExt: Sealed {
     /// Calls the table as function assuming it has `__call` metamethod.
     ///
-    /// The metamethod is called with the table as its first argument, followed by the passed arguments.
+    /// The metamethod is called with the table 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>;
+        A: IntoLuaMulti,
+        R: FromLuaMulti;
 
     /// Asynchronously calls the table as function assuming it has `__call` metamethod.
     ///
-    /// The metamethod is called with the table as its first argument, followed by the passed arguments.
+    /// The metamethod is called with the table 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>>
+    fn call_async<A, R>(&self, args: A) -> impl Future<Output = Result<R>>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua;
+        A: IntoLuaMulti,
+        R: FromLuaMulti;
 
     /// Gets the function associated to `key` from the table and executes it,
     /// passing the table itself along with `args` as function arguments.
@@ -933,8 +889,8 @@ pub trait TableExt<'lua>: Sealed {
     /// This might invoke the `__index` metamethod.
     fn call_method<A, R>(&self, name: &str, args: A) -> Result<R>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua>;
+        A: IntoLuaMulti,
+        R: FromLuaMulti;
 
     /// Gets the function associated to `key` from the table and executes it,
     /// passing `args` as function arguments.
@@ -945,8 +901,8 @@ pub trait TableExt<'lua>: Sealed {
     /// 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>;
+        A: IntoLuaMulti,
+        R: FromLuaMulti;
 
     /// 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.
@@ -956,10 +912,10 @@ pub trait TableExt<'lua>: Sealed {
     /// 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>>
+    fn call_async_method<A, R>(&self, name: &str, args: A) -> impl Future<Output = Result<R>>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua;
+        A: IntoLuaMulti,
+        R: FromLuaMulti;
 
     /// Gets the function associated to `key` from the table and asynchronously executes it,
     /// passing `args` as function arguments and returning Future.
@@ -969,98 +925,86 @@ pub trait TableExt<'lua>: Sealed {
     /// 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>>
+    fn call_async_function<A, R>(&self, name: &str, args: A) -> impl Future<Output = Result<R>>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua;
+        A: IntoLuaMulti,
+        R: FromLuaMulti;
 }
 
-impl<'lua> TableExt<'lua> for Table<'lua> {
+impl TableExt for Table {
     fn call<A, R>(&self, args: A) -> Result<R>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua>,
+        A: IntoLuaMulti,
+        R: FromLuaMulti,
     {
         // Convert table to a function and call via pcall that respects the `__call` metamethod.
         Function(self.0.clone()).call(args)
     }
 
     #[cfg(feature = "async")]
-    fn call_async<A, R>(&self, args: A) -> LocalBoxFuture<'lua, Result<R>>
+    fn call_async<A, R>(&self, args: A) -> impl Future<Output = Result<R>>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua,
+        A: IntoLuaMulti,
+        R: FromLuaMulti,
     {
-        let args = match args.into_lua_multi(self.0.lua) {
-            Ok(args) => args,
-            Err(e) => return Box::pin(future::err(e)),
-        };
-        let func = Function(self.0.clone());
-        Box::pin(async move { func.call_async(args).await })
+        let lua = self.0.lua.lock();
+        let args = args.into_lua_multi(lua.lua());
+        async move {
+            let func = Function(self.0.clone());
+            func.call_async(args?).await
+        }
     }
 
     fn call_method<A, R>(&self, name: &str, args: A) -> Result<R>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua>,
+        A: IntoLuaMulti,
+        R: FromLuaMulti,
     {
-        let lua = self.0.lua;
-        let mut args = args.into_lua_multi(lua)?;
-        args.push_front(Value::Table(self.clone()));
-        self.get::<_, Function>(name)?.call(args)
+        self.get::<_, Function>(name)?.call((self, args))
     }
 
     fn call_function<A, R>(&self, name: &str, args: A) -> Result<R>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua>,
+        A: IntoLuaMulti,
+        R: FromLuaMulti,
     {
         self.get::<_, Function>(name)?.call(args)
     }
 
     #[cfg(feature = "async")]
-    fn call_async_method<A, R>(&self, name: &str, args: A) -> LocalBoxFuture<'lua, Result<R>>
+    fn call_async_method<A, R>(&self, name: &str, args: A) -> impl Future<Output = Result<R>>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua,
+        A: IntoLuaMulti,
+        R: FromLuaMulti,
     {
-        let lua = self.0.lua;
-        let mut args = match args.into_lua_multi(lua) {
-            Ok(args) => args,
-            Err(e) => return Box::pin(future::err(e)),
-        };
-        args.push_front(Value::Table(self.clone()));
-        self.call_async_function(name, args)
+        self.call_async_function(name, (self, args))
     }
 
     #[cfg(feature = "async")]
-    fn call_async_function<A, R>(&self, name: &str, args: A) -> LocalBoxFuture<'lua, Result<R>>
+    fn call_async_function<A, R>(&self, name: &str, args: A) -> impl Future<Output = Result<R>>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua,
+        A: IntoLuaMulti,
+        R: FromLuaMulti,
     {
-        let lua = self.0.lua;
-        let args = match args.into_lua_multi(lua) {
-            Ok(args) => args,
-            Err(e) => return Box::pin(future::err(e)),
-        };
-        match self.get::<_, Function>(name) {
-            Ok(func) => Box::pin(async move { func.call_async(args).await }),
-            Err(e) => Box::pin(future::err(e)),
+        let lua = self.0.lua.lock();
+        let args = args.into_lua_multi(lua.lua());
+        async move {
+            let func = self.get::<_, Function>(name)?;
+            func.call_async(args?).await
         }
     }
 }
 
 /// A wrapped [`Table`] with customized serialization behavior.
 #[cfg(feature = "serialize")]
-pub(crate) struct SerializableTable<'a, 'lua> {
-    table: &'a Table<'lua>,
+pub(crate) struct SerializableTable<'a> {
+    table: &'a Table,
     options: crate::serde::de::Options,
     visited: Rc<RefCell<FxHashSet<*const c_void>>>,
 }
 
 #[cfg(feature = "serialize")]
-impl<'lua> Serialize for Table<'lua> {
+impl Serialize for Table {
     #[inline]
     fn serialize<S: Serializer>(&self, serializer: S) -> StdResult<S::Ok, S::Error> {
         SerializableTable::new(self, Default::default(), Default::default()).serialize(serializer)
@@ -1068,10 +1012,10 @@ impl<'lua> Serialize for Table<'lua> {
 }
 
 #[cfg(feature = "serialize")]
-impl<'a, 'lua> SerializableTable<'a, 'lua> {
+impl<'a> SerializableTable<'a> {
     #[inline]
     pub(crate) fn new(
-        table: &'a Table<'lua>,
+        table: &'a Table,
         options: crate::serde::de::Options,
         visited: Rc<RefCell<FxHashSet<*const c_void>>>,
     ) -> Self {
@@ -1084,7 +1028,7 @@ impl<'a, 'lua> SerializableTable<'a, 'lua> {
 }
 
 #[cfg(feature = "serialize")]
-impl<'a, 'lua> Serialize for SerializableTable<'a, 'lua> {
+impl<'a> Serialize for SerializableTable<'a> {
     fn serialize<S>(&self, serializer: S) -> StdResult<S::Ok, S::Error>
     where
         S: Serializer,
@@ -1151,7 +1095,7 @@ impl<'a, 'lua> Serialize for SerializableTable<'a, 'lua> {
             // Fast track
             self.table.for_each(process_pair)
         } else {
-            MapPairs::new(self.table.clone(), self.options.sort_keys)
+            MapPairs::new(self.table, self.options.sort_keys)
                 .map_err(serde::ser::Error::custom)?
                 .try_for_each(|kv| {
                     let (key, value) = kv?;
@@ -1168,30 +1112,31 @@ impl<'a, 'lua> Serialize for SerializableTable<'a, 'lua> {
 /// This struct is created by the [`Table::pairs`] method.
 ///
 /// [`Table::pairs`]: crate::Table::pairs
-pub struct TablePairs<'lua, K, V> {
-    table: LuaRef<'lua>,
-    key: Option<Value<'lua>>,
+pub struct TablePairs<'a, K, V> {
+    guard: LuaGuard,
+    table: &'a Table,
+    key: Option<Value>,
     _phantom: PhantomData<(K, V)>,
 }
 
-impl<'lua, K, V> Iterator for TablePairs<'lua, K, V>
+impl<'a, K, V> Iterator for TablePairs<'a, K, V>
 where
-    K: FromLua<'lua>,
-    V: FromLua<'lua>,
+    K: FromLua,
+    V: FromLua,
 {
     type Item = Result<(K, V)>;
 
     fn next(&mut self) -> Option<Self::Item> {
         if let Some(prev_key) = self.key.take() {
-            let lua = self.table.lua;
+            let lua: &RawLua = &self.guard;
             let state = lua.state();
 
             let res = (|| unsafe {
                 let _sg = StackGuard::new(state);
                 check_stack(state, 5)?;
 
-                lua.push_ref(&self.table);
-                lua.push_value(prev_key)?;
+                lua.push_ref(&self.table.0);
+                lua.push_value(&prev_key)?;
 
                 // It must be safe to call `lua_next` unprotected as deleting a key from a table is
                 // a permitted operation.
@@ -1200,8 +1145,8 @@ where
                     let key = lua.stack_value(-2);
                     Ok(Some((
                         key.clone(),
-                        K::from_lua(key, lua)?,
-                        V::from_stack(-1, lua)?,
+                        K::from_lua(key, lua.lua())?,
+                        V::from_stack(-1, &lua)?,
                     )))
                 } else {
                     Ok(None)
@@ -1227,21 +1172,21 @@ where
 /// This struct is created by the [`Table::sequence_values`] method.
 ///
 /// [`Table::sequence_values`]: crate::Table::sequence_values
-pub struct TableSequence<'lua, V> {
-    // TODO: Use `&Table`
-    table: LuaRef<'lua>,
+pub struct TableSequence<'a, V> {
+    guard: LuaGuard,
+    table: &'a Table,
     index: Integer,
     _phantom: PhantomData<V>,
 }
 
-impl<'lua, V> Iterator for TableSequence<'lua, V>
+impl<'a, V> Iterator for TableSequence<'a, V>
 where
-    V: FromLua<'lua>,
+    V: FromLua,
 {
     type Item = Result<V>;
 
     fn next(&mut self) -> Option<Self::Item> {
-        let lua = self.table.lua;
+        let lua: &RawLua = &self.guard;
         let state = lua.state();
         unsafe {
             let _sg = StackGuard::new(state);
@@ -1249,12 +1194,12 @@ where
                 return Some(Err(err));
             }
 
-            lua.push_ref(&self.table);
+            lua.push_ref(&self.table.0);
             match ffi::lua_rawgeti(state, -1, self.index) {
                 ffi::LUA_TNIL => None,
                 _ => {
                     self.index += 1;
-                    Some(V::from_stack(-1, lua))
+                    Some(V::from_stack(-1, &lua))
                 }
             }
         }
@@ -1265,8 +1210,8 @@ where
 mod assertions {
     use super::*;
 
+    #[cfg(not(feature = "send"))]
     static_assertions::assert_not_impl_any!(Table: Send);
-
-    #[cfg(feature = "unstable")]
-    static_assertions::assert_not_impl_any!(OwnedTable: Send);
+    #[cfg(feature = "send")]
+    static_assertions::assert_impl_all!(Table: Send, Sync);
 }

src/thread.rs

@@ -2,8 +2,9 @@ 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};
 
@@ -43,31 +44,12 @@ pub enum ThreadStatus {
 
 /// 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 +60,15 @@ 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<R> {
+    thread: Thread,
+    init_args: Option<Result<MultiValue>>,
     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
     }
@@ -139,14 +116,15 @@ impl<'lua> Thread<'lua> {
     /// ```
     pub fn resume<A, R>(&self, args: A) -> Result<R>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua>,
+        A: IntoLuaMulti,
+        R: FromLuaMulti,
     {
-        if self.status() != ThreadStatus::Resumable {
+        let lua = self.0.lua.lock();
+
+        if unsafe { self.status_unprotected() } != ThreadStatus::Resumable {
             return Err(Error::CoroutineInactive);
         }
 
-        let lua = self.0.lua;
         let state = lua.state();
         let thread_state = self.state();
         unsafe {
@@ -157,19 +135,19 @@ impl<'lua> Thread<'lua> {
             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<A: IntoLuaMulti>(&self, args: A) -> Result<c_int> {
+        let lua = self.0.lua.lock();
         let state = lua.state();
         let thread_state = self.state();
 
-        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 +161,7 @@ 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));
         }
 
@@ -195,20 +170,25 @@ impl<'lua> Thread<'lua> {
 
     /// Gets the status of the thread.
     pub fn status(&self) -> ThreadStatus {
+        let _guard = self.0.lua.lock();
+        unsafe { self.status_unprotected() }
+    }
+
+    /// Gets the status of the thread without locking the Lua state.
+    pub(crate) unsafe fn status_unprotected(&self) -> ThreadStatus {
         let thread_state = self.state();
-        if thread_state == self.0.lua.state() {
+        // FIXME: skip double lock
+        if thread_state == self.0.lua.lock().state() {
             // The coroutine is currently running
             return ThreadStatus::Unresumable;
         }
-        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
-            }
+        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
         }
     }
 
@@ -222,7 +202,7 @@ 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);
         }
@@ -244,8 +224,8 @@ 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();
         let thread_state = self.state();
         if thread_state == lua.state() {
             return Err(Error::runtime("cannot reset a running thread"));
@@ -296,7 +276,7 @@ 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();
@@ -323,12 +303,13 @@ 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<A, R>(self, args: A) -> AsyncThread<R>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua>,
+        A: IntoLuaMulti,
+        R: FromLuaMulti,
     {
-        let args = args.into_lua_multi(self.0.lua);
+        let lua = self.0.lua.lock();
+        let args = args.into_lua_multi(lua.lua());
         AsyncThread {
             thread: self,
             init_args: Some(args),
@@ -372,7 +353,7 @@ 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 {
@@ -391,44 +372,16 @@ impl<'lua> Thread<'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) -> OwnedThread {
-        OwnedThread(self.0.into_owned(), self.1)
-    }
 }
 
-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<R> AsyncThread<R> {
     #[inline]
     pub(crate) fn set_recyclable(&mut self, recyclable: bool) {
         self.recycle = recyclable;
@@ -437,15 +390,15 @@ impl<'lua, R> AsyncThread<'lua, R> {
 
 #[cfg(feature = "async")]
 #[cfg(any(feature = "lua54", feature = "luau"))]
-impl<'lua, R> Drop for AsyncThread<'lua, R> {
+impl<R> Drop for AsyncThread<R> {
     fn drop(&mut self) {
         if self.recycle {
             unsafe {
-                let lua = self.thread.0.lua;
+                let lua = self.thread.0.lua.lock();
                 // 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 {
+                    if self.thread.status_unprotected() == ThreadStatus::Error {
                         #[cfg(not(feature = "vendored"))]
                         ffi::lua_resetthread(self.thread.state());
                         #[cfg(feature = "vendored")]
@@ -458,24 +411,21 @@ impl<'lua, R> Drop for AsyncThread<'lua, R> {
 }
 
 #[cfg(feature = "async")]
-impl<'lua, R> Stream for AsyncThread<'lua, R>
-where
-    R: FromLuaMulti<'lua>,
-{
+impl<R: FromLuaMulti> Stream for AsyncThread<R> {
     type Item = Result<R>;
 
     fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
-        if self.thread.status() != ThreadStatus::Resumable {
-            return Poll::Ready(None);
-        }
-
-        let lua = self.thread.0.lua;
+        let lua = self.thread.0.lua.lock();
         let state = lua.state();
         let thread_state = self.thread.state();
         unsafe {
+            if self.thread.status_unprotected() != ThreadStatus::Resumable {
+                return Poll::Ready(None);
+            }
+
             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();
@@ -493,30 +443,27 @@ 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<R: FromLuaMulti> Future for AsyncThread<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;
+        let lua = self.thread.0.lua.lock();
         let state = lua.state();
         let thread_state = self.thread.state();
         unsafe {
+            if self.thread.status_unprotected() != ThreadStatus::Resumable {
+                return Poll::Ready(Err(Error::CoroutineInactive));
+            }
+
             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();
@@ -539,7 +486,7 @@ 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))
         }
     }
 }
@@ -552,7 +499,7 @@ unsafe fn is_poll_pending(state: *mut ffi::lua_State) -> bool {
 
 #[cfg(feature = "async")]
 struct WakerGuard<'lua, 'a> {
-    lua: &'lua Lua,
+    lua: &'lua RawLua,
     prev: NonNull<Waker>,
     _phantom: PhantomData<&'a ()>,
 }
@@ -560,7 +507,7 @@ 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,
@@ -581,5 +528,8 @@ 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);
 }

src/types.rs

@@ -1,29 +1,27 @@
-use std::any::{Any, TypeId};
-use std::cell::{Cell, Ref, RefCell, RefMut, UnsafeCell};
+use std::cell::UnsafeCell;
 use std::hash::{Hash, Hasher};
-use std::ops::{Deref, DerefMut};
 use std::os::raw::{c_int, c_void};
-use std::result::Result as StdResult;
-use std::sync::atomic::{AtomicI32, Ordering};
-use std::sync::{Arc, Mutex};
+use std::rc::Rc;
+use std::sync::Arc;
 use std::{fmt, mem, ptr};
 
-use rustc_hash::FxHashMap;
+use parking_lot::Mutex;
 
 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};
 
-#[cfg(feature = "unstable")]
-use {crate::lua::LuaInner, std::marker::PhantomData};
-
 #[cfg(all(feature = "luau", feature = "serialize"))]
 use serde::ser::{Serialize, SerializeTupleStruct, Serializer};
 
+// Re-export mutex wrappers
+pub use app_data::{AppData, AppDataRef, AppDataRefMut};
+pub(crate) use sync::{ArcReentrantMutexGuard, ReentrantMutex, ReentrantMutexGuard, XRc, XWeak};
+
 /// Type of Lua integer numbers.
 pub type Integer = ffi::lua_Integer;
 /// Type of Lua floating point numbers.
@@ -43,21 +41,26 @@ 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 {}
+
+pub(crate) type Callback<'a> = Box<dyn Fn(&'a 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<'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 AsyncCallback<'a> =
+    Box<dyn Fn(&'a RawLua, MultiValue) -> LocalBoxFuture<'a, Result<c_int>> + 'static>;
 
 #[cfg(feature = "async")]
-pub(crate) type AsyncCallbackUpvalue = Upvalue<AsyncCallback<'static, 'static>>;
+pub(crate) type AsyncCallbackUpvalue = Upvalue<AsyncCallback<'static>>;
 
 #[cfg(feature = "async")]
 pub(crate) type AsyncPollUpvalue = Upvalue<LocalBoxFuture<'static, Result<c_int>>>;
@@ -71,16 +74,16 @@ 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>;
@@ -165,7 +168,7 @@ impl Vector {
 
 #[cfg(all(feature = "luau", feature = "serialize"))]
 impl Serialize for Vector {
-    fn serialize<S: Serializer>(&self, serializer: S) -> StdResult<S::Ok, S::Error> {
+    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())?;
@@ -190,7 +193,8 @@ pub(crate) struct DestructedUserdata;
 ///
 /// 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`].
+/// 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.
@@ -204,7 +208,7 @@ pub(crate) struct DestructedUserdata;
 /// [`AnyUserData::set_user_value`]: crate::AnyUserData::set_user_value
 /// [`AnyUserData::user_value`]: crate::AnyUserData::user_value
 pub struct RegistryKey {
-    pub(crate) registry_id: AtomicI32,
+    pub(crate) registry_id: i32,
     pub(crate) unref_list: Arc<Mutex<Option<Vec<c_int>>>>,
 }
 
@@ -233,7 +237,7 @@ impl Drop for RegistryKey {
         let registry_id = self.id();
         // We don't need to collect nil slot
         if registry_id > ffi::LUA_REFNIL {
-            let mut unref_list = mlua_expect!(self.unref_list.lock(), "unref list poisoned");
+            let mut unref_list = self.unref_list.lock();
             if let Some(list) = unref_list.as_mut() {
                 list.push(registry_id);
             }
@@ -245,7 +249,7 @@ 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: AtomicI32::new(id),
+            registry_id: id,
             unref_list,
         }
     }
@@ -253,13 +257,13 @@ impl RegistryKey {
     /// Returns the underlying Lua reference of this `RegistryKey`
     #[inline(always)]
     pub fn id(&self) -> c_int {
-        self.registry_id.load(Ordering::Relaxed)
+        self.registry_id
     }
 
     /// Sets the unique Lua reference key of this `RegistryKey`
     #[inline(always)]
-    pub(crate) fn set_id(&self, id: c_int) {
-        self.registry_id.store(id, Ordering::Relaxed);
+    pub(crate) fn set_id(&mut self, id: c_int) {
+        self.registry_id = id;
     }
 
     /// Destroys the `RegistryKey` without adding to the unref list
@@ -273,16 +277,17 @@ impl RegistryKey {
     }
 }
 
-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,
         }
@@ -290,249 +295,55 @@ impl<'lua> LuaRef<'lua> {
 
     #[inline]
     pub(crate) fn to_pointer(&self) -> *const c_void {
-        unsafe { ffi::lua_topointer(self.lua.ref_thread(), self.index) }
-    }
-
-    #[cfg(feature = "unstable")]
-    #[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
+        let lua = self.lua.lock();
+        unsafe { ffi::lua_topointer(lua.ref_thread(), self.index) }
     }
 }
 
-impl<'lua> fmt::Debug for LuaRef<'lua> {
+impl fmt::Debug for ValueRef {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "Ref({:p})", self.to_pointer())
     }
 }
 
-impl<'lua> Clone for LuaRef<'lua> {
+impl Clone for ValueRef {
     fn clone(&self) -> Self {
-        self.lua.clone_ref(self)
+        unsafe { self.lua.lock().clone_ref(self) }
     }
 }
 
-impl<'lua> Drop for LuaRef<'lua> {
+impl Drop for ValueRef {
     fn drop(&mut self) {
         if self.drop {
-            self.lua.drop_ref_index(self.index);
+            if let Some(lua) = self.lua.try_lock() {
+                unsafe { lua.drop_ref(self) };
+            }
         }
     }
 }
 
-impl<'lua> PartialEq for LuaRef<'lua> {
+impl PartialEq for ValueRef {
     fn eq(&self, other: &Self) -> bool {
-        let ref_thread = self.lua.ref_thread();
         assert!(
-            ref_thread == other.lua.ref_thread(),
+            self.lua == other.lua,
             "Lua instance passed Value created from a different main Lua state"
         );
-        unsafe { ffi::lua_rawequal(ref_thread, self.index, other.index) == 1 }
+        let lua = self.lua.lock();
+        unsafe { ffi::lua_rawequal(lua.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) },
-            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)
-    }
-}
-
-/// 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<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>,
-}
-
-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)
-    }
-}
+mod app_data;
+mod sync;
 
 #[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/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/userdata/cell.rs

@@ -0,0 +1,422 @@
+use std::any::{type_name, TypeId};
+use std::cell::{Cell, UnsafeCell};
+use std::fmt;
+use std::ops::{Deref, DerefMut};
+use std::os::raw::c_int;
+use std::rc::Rc;
+
+#[cfg(feature = "serialize")]
+use serde::ser::{Serialize, Serializer};
+
+use crate::error::{Error, Result};
+use crate::state::{Lua, LuaGuard, RawLua};
+use crate::userdata::AnyUserData;
+use crate::util::get_userdata;
+use crate::value::{FromLua, Value};
+
+// 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(Rc<InnerRefCell<T>>),
+    #[cfg(feature = "serialize")]
+    Serializable(Rc<InnerRefCell<Box<dyn erased_serde::Serialize>>>),
+}
+
+impl<T> Clone for UserDataVariant<T> {
+    #[inline]
+    fn clone(&self) -> Self {
+        match self {
+            Self::Default(inner) => Self::Default(Rc::clone(inner)),
+            #[cfg(feature = "serialize")]
+            Self::Serializable(inner) => UserDataVariant::Serializable(Rc::clone(inner)),
+        }
+    }
+}
+
+impl<T> UserDataVariant<T> {
+    #[inline(always)]
+    pub(crate) fn new(data: T) -> Self {
+        Self::Default(Rc::new(InnerRefCell::new(data)))
+    }
+
+    // Immutably borrows the wrapped value in-place.
+    #[inline(always)]
+    pub(crate) unsafe 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_make_ref(&self, guard: LuaGuard) -> Result<UserDataRef<T>> {
+        UserDataRef::try_from(self.clone(), guard)
+    }
+
+    // Mutably borrows the wrapped value in-place.
+    #[inline(always)]
+    pub(crate) unsafe 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_make_mut_ref(&self, guard: LuaGuard) -> Result<UserDataRefMut<T>> {
+        UserDataRefMut::try_from(self.clone(), guard)
+    }
+
+    // Returns the wrapped value.
+    //
+    // This method checks that we have exclusive access to the value.
+    pub(crate) fn into_inner(self) -> Result<T> {
+        set_writing(self.flag())?;
+        Ok(match self {
+            Self::Default(inner) => Rc::into_inner(inner).unwrap().value.into_inner(),
+            #[cfg(feature = "serialize")]
+            Self::Serializable(inner) => unsafe {
+                let raw = Box::into_raw(Rc::into_inner(inner).unwrap().value.into_inner());
+                *Box::from_raw(raw as *mut T)
+            },
+        })
+    }
+
+    #[inline(always)]
+    fn flag(&self) -> &Cell<BorrowFlag> {
+        match self {
+            Self::Default(inner) => &inner.borrow,
+            #[cfg(feature = "serialize")]
+            Self::Serializable(inner) => &inner.borrow,
+        }
+    }
+
+    #[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 + 'static> UserDataVariant<T> {
+    #[inline(always)]
+    pub(crate) fn new_ser(data: T) -> Self {
+        let data = Box::new(data) as Box<dyn erased_serde::Serialize>;
+        Self::Serializable(Rc::new(InnerRefCell::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 {
+            UserDataVariant::Default(_) => Err(serde::ser::Error::custom("cannot serialize <userdata>")),
+            UserDataVariant::Serializable(inner) => unsafe {
+                let _ = self.try_borrow().map_err(serde::ser::Error::custom)?;
+                (*inner.value.get()).serialize(serializer)
+            },
+        }
+    }
+}
+
+//
+// Inspired by `std::cell::RefCell`` implementation
+//
+
+pub(crate) struct InnerRefCell<T> {
+    borrow: Cell<BorrowFlag>,
+    value: UnsafeCell<T>,
+}
+
+impl<T> InnerRefCell<T> {
+    #[inline(always)]
+    pub fn new(value: T) -> Self {
+        InnerRefCell {
+            borrow: Cell::new(UNUSED),
+            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> {
+    variant: UserDataVariant<T>,
+    #[allow(unused)]
+    guard: LuaGuard,
+}
+
+impl<T> Deref for UserDataRef<T> {
+    type Target = T;
+
+    #[inline]
+    fn deref(&self) -> &T {
+        unsafe { &*self.variant.as_ptr() }
+    }
+}
+
+impl<T> Drop for UserDataRef<T> {
+    #[inline]
+    fn drop(&mut self) {
+        unset_reading(self.variant.flag());
+    }
+}
+
+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> UserDataRef<T> {
+    #[inline]
+    fn try_from(variant: UserDataVariant<T>, guard: LuaGuard) -> Result<Self> {
+        set_reading(variant.flag())?;
+        Ok(UserDataRef { variant, guard })
+    }
+}
+
+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>() => {
+                let guard = lua.lua().lock_arc();
+                (*get_userdata::<UserDataVariant<T>>(lua.state(), idx)).try_make_ref(guard)
+            }
+            _ => 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> {
+    variant: UserDataVariant<T>,
+    #[allow(unused)]
+    guard: LuaGuard,
+}
+
+impl<T> Deref for UserDataRefMut<T> {
+    type Target = T;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        unsafe { &*self.variant.as_ptr() }
+    }
+}
+
+impl<T> DerefMut for UserDataRefMut<T> {
+    #[inline]
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        unsafe { &mut *self.variant.as_ptr() }
+    }
+}
+
+impl<T> Drop for UserDataRefMut<T> {
+    #[inline]
+    fn drop(&mut self) {
+        unset_writing(self.variant.flag());
+    }
+}
+
+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> UserDataRefMut<T> {
+    fn try_from(variant: UserDataVariant<T>, guard: LuaGuard) -> Result<Self> {
+        // There must currently be no existing references
+        set_writing(variant.flag())?;
+        Ok(UserDataRefMut { variant, guard })
+    }
+}
+
+impl<T: 'static> FromLua for UserDataRefMut<T> {
+    fn from_lua(value: Value, _: &Lua) -> Result<Self> {
+        try_value_to_userdata::<T>(value)?.borrow_mut()
+    }
+
+    unsafe fn from_stack(idx: c_int, lua: &RawLua) -> Result<Self> {
+        let type_id = lua.get_userdata_type_id(idx)?;
+        match type_id {
+            Some(type_id) if type_id == TypeId::of::<T>() => {
+                let guard = lua.lua().lock_arc();
+                (*get_userdata::<UserDataVariant<T>>(lua.state(), idx)).try_make_mut_ref(guard)
+            }
+            _ => Err(Error::UserDataTypeMismatch),
+        }
+    }
+}
+
+// Positive values represent the number of `Ref` active. Negative values
+// represent the number of `RefMut` active. Multiple `RefMut`s can only be
+// active at a time if they refer to distinct, nonoverlapping components of a
+// `RefCell` (e.g., different ranges of a slice).
+type BorrowFlag = isize;
+const UNUSED: BorrowFlag = 0;
+
+#[inline(always)]
+fn is_writing(x: BorrowFlag) -> bool {
+    x < UNUSED
+}
+
+#[inline(always)]
+fn is_reading(x: BorrowFlag) -> bool {
+    x > UNUSED
+}
+
+#[inline(always)]
+fn set_writing(borrow: &Cell<BorrowFlag>) -> Result<()> {
+    let flag = borrow.get();
+    if flag != UNUSED {
+        return Err(Error::UserDataBorrowMutError);
+    }
+    borrow.set(UNUSED - 1);
+    Ok(())
+}
+
+#[inline(always)]
+fn set_reading(borrow: &Cell<BorrowFlag>) -> Result<()> {
+    let flag = borrow.get().wrapping_add(1);
+    if !is_reading(flag) {
+        return Err(Error::UserDataBorrowError);
+    }
+    borrow.set(flag);
+    Ok(())
+}
+
+#[inline(always)]
+#[track_caller]
+fn unset_writing(borrow: &Cell<BorrowFlag>) {
+    let flag = borrow.get();
+    debug_assert!(is_writing(flag));
+    borrow.set(flag + 1);
+}
+
+#[inline(always)]
+#[track_caller]
+fn unset_reading(borrow: &Cell<BorrowFlag>) {
+    let flag = borrow.get();
+    debug_assert!(is_reading(flag));
+    borrow.set(flag - 1);
+}
+
+pub(crate) struct UserDataBorrowRef<'a, T>(&'a UserDataVariant<T>);
+
+impl<'a, T> Drop for UserDataBorrowRef<'a, T> {
+    #[inline]
+    fn drop(&mut self) {
+        unset_reading(self.0.flag());
+    }
+}
+
+impl<'a, T> Deref for UserDataBorrowRef<'a, T> {
+    type Target = T;
+
+    #[inline]
+    fn deref(&self) -> &T {
+        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> {
+        set_reading(variant.flag())?;
+        Ok(UserDataBorrowRef(variant))
+    }
+}
+
+impl<'a, T> UserDataBorrowRef<'a, T> {
+    #[inline(always)]
+    pub(crate) fn get_ref(&self) -> &'a T {
+        // SAFETY: `UserDataBorrowRef` is only created when the borrow flag is set to reading.
+        unsafe { &*self.0.as_ptr() }
+    }
+}
+
+pub(crate) struct UserDataBorrowMut<'a, T>(&'a UserDataVariant<T>);
+
+impl<'a, T> Drop for UserDataBorrowMut<'a, T> {
+    #[inline]
+    fn drop(&mut self) {
+        unset_writing(self.0.flag());
+    }
+}
+
+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> {
+        set_writing(variant.flag())?;
+        Ok(UserDataBorrowMut(variant))
+    }
+}
+
+impl<'a, T> UserDataBorrowMut<'a, T> {
+    #[inline(always)]
+    pub(crate) fn get_mut(&mut self) -> &'a mut T {
+        // SAFETY: `UserDataBorrowMut` is only created when the borrow flag is set to writing.
+        unsafe { &mut *self.0.as_ptr() }
+    }
+}
+
+#[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::*;
+
+    static_assertions::assert_not_impl_all!(UserDataRef<()>: Sync, Send);
+    static_assertions::assert_not_impl_all!(UserDataRefMut<()>: Sync, Send);
+}

src/userdata/ext.rs

@@ -4,40 +4,42 @@ use crate::userdata::{AnyUserData, MetaMethod};
 use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, Value};
 
 #[cfg(feature = "async")]
-use futures_util::future::{self, LocalBoxFuture};
+use std::future::Future;
 
 /// An extension trait for [`AnyUserData`] that provides a variety of convenient functionality.
-pub trait AnyUserDataExt<'lua>: Sealed {
+pub trait AnyUserDataExt: 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>;
+    fn get<K: IntoLua, V: FromLua>(&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<()>;
+    fn set<K: IntoLua, V: IntoLua>(&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.
+    /// 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>;
+        A: IntoLuaMulti,
+        R: FromLuaMulti;
 
     /// 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.
+    /// 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>>
+    fn call_async<A, R>(&self, args: A) -> impl Future<Output = Result<R>>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua;
+        A: IntoLuaMulti,
+        R: FromLuaMulti;
 
     /// 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>;
+        A: IntoLuaMulti,
+        R: FromLuaMulti;
 
     /// 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.
@@ -47,10 +49,10 @@ pub trait AnyUserDataExt<'lua>: Sealed {
     /// 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>>
+    fn call_async_method<A, R>(&self, name: &str, args: A) -> impl Future<Output = Result<R>>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua;
+        A: IntoLuaMulti,
+        R: FromLuaMulti;
 
     /// Gets the function associated to `key` from the table and executes it,
     /// passing `args` as function arguments.
@@ -61,8 +63,8 @@ pub trait AnyUserDataExt<'lua>: Sealed {
     /// 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>;
+        A: IntoLuaMulti,
+        R: FromLuaMulti;
 
     /// Gets the function associated to `key` from the table and asynchronously executes it,
     /// passing `args` as function arguments and returning Future.
@@ -72,90 +74,81 @@ pub trait AnyUserDataExt<'lua>: Sealed {
     /// 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>>
+    fn call_async_function<A, R>(&self, name: &str, args: A) -> impl Future<Output = Result<R>>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua;
+        A: IntoLuaMulti,
+        R: FromLuaMulti;
 }
 
-impl<'lua> AnyUserDataExt<'lua> for AnyUserData<'lua> {
-    fn get<K: IntoLua<'lua>, V: FromLua<'lua>>(&self, key: K) -> Result<V> {
+impl AnyUserDataExt for AnyUserData {
+    fn get<K: IntoLua, V: FromLua>(&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)),
+            Value::Function(func) => func.call((self, key)),
             _ => Err(Error::runtime("attempt to index a userdata value")),
         }
     }
 
-    fn set<K: IntoLua<'lua>, V: IntoLua<'lua>>(&self, key: K, value: V) -> Result<()> {
+    fn set<K: IntoLua, V: IntoLua>(&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)),
+            Value::Function(func) => func.call((self, 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>,
+        A: IntoLuaMulti,
+        R: FromLuaMulti,
     {
         let metatable = self.get_metatable()?;
         match metatable.get::<Value>(MetaMethod::Call)? {
-            Value::Function(func) => func.call((self.clone(), args)),
+            Value::Function(func) => func.call((self, 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>>
+    fn call_async<A, R>(&self, args: A) -> impl Future<Output = Result<R>>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua,
+        A: IntoLuaMulti,
+        R: FromLuaMulti,
     {
-        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 })
+        let lua = self.0.lua.lock();
+        let args = (self, args).into_lua_multi(lua.lua());
+        async move {
+            let metatable = self.get_metatable()?;
+            match metatable.get::<Value>(MetaMethod::Call)? {
+                Value::Function(func) => func.call_async(args?).await,
+                _ => Err(Error::runtime("attempt to call a userdata value")),
             }
-            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>,
+        A: IntoLuaMulti,
+        R: FromLuaMulti,
     {
-        self.call_function(name, (self.clone(), args))
+        self.call_function(name, (self, args))
     }
 
     #[cfg(feature = "async")]
-    fn call_async_method<A, R>(&self, name: &str, args: A) -> LocalBoxFuture<'lua, Result<R>>
+    fn call_async_method<A, R>(&self, name: &str, args: A) -> impl Future<Output = Result<R>>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua,
+        A: IntoLuaMulti,
+        R: FromLuaMulti,
     {
-        self.call_async_function(name, (self.clone(), args))
+        self.call_async_function(name, (self, args))
     }
 
     fn call_function<A, R>(&self, name: &str, args: A) -> Result<R>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua>,
+        A: IntoLuaMulti,
+        R: FromLuaMulti,
     {
         match self.get(name)? {
             Value::Function(func) => func.call(args),
@@ -167,24 +160,21 @@ impl<'lua> AnyUserDataExt<'lua> for AnyUserData<'lua> {
     }
 
     #[cfg(feature = "async")]
-    fn call_async_function<A, R>(&self, name: &str, args: A) -> LocalBoxFuture<'lua, Result<R>>
+    fn call_async_function<A, R>(&self, name: &str, args: A) -> impl Future<Output = Result<R>>
     where
-        A: IntoLuaMulti<'lua>,
-        R: FromLuaMulti<'lua> + 'lua,
+        A: IntoLuaMulti,
+        R: FromLuaMulti,
     {
-        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 })
+        let lua = self.0.lua.lock();
+        let args = args.into_lua_multi(lua.lua());
+        async move {
+            match self.get::<_, Value>(name)? {
+                Value::Function(func) => func.call_async(args?).await,
+                val => {
+                    let msg = format!("attempt to call a {} value", val.type_name());
+                    Err(Error::runtime(msg))
+                }
             }
-            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/registry.rs

@@ -0,0 +1,591 @@
+#![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;
+use crate::types::{Callback, MaybeSend};
+use crate::userdata::{AnyUserData, MetaMethod, UserData, UserDataFields, UserDataMethods};
+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},
+};
+
+/// Handle to registry for userdata methods and metamethods.
+pub struct UserDataRegistry<'a, T: 'static> {
+    // Fields
+    pub(crate) fields: Vec<(String, Callback<'a>)>,
+    pub(crate) field_getters: Vec<(String, Callback<'a>)>,
+    pub(crate) field_setters: Vec<(String, Callback<'a>)>,
+    pub(crate) meta_fields: Vec<(String, Callback<'a>)>,
+
+    // Methods
+    pub(crate) methods: Vec<(String, Callback<'a>)>,
+    #[cfg(feature = "async")]
+    pub(crate) async_methods: Vec<(String, AsyncCallback<'a>)>,
+    pub(crate) meta_methods: Vec<(String, Callback<'a>)>,
+    #[cfg(feature = "async")]
+    pub(crate) async_meta_methods: Vec<(String, AsyncCallback<'a>)>,
+
+    _type: PhantomData<T>,
+}
+
+impl<'a, T: 'static> UserDataRegistry<'a, 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<'a>
+    where
+        M: Fn(&'a 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) => {
+                $res.map_err(|err| Error::bad_self_argument(&name, err))?
+            };
+        }
+
+        Box::new(move |rawlua, nargs| unsafe {
+            if nargs == 0 {
+                let err = Error::from_lua_conversion("missing argument", "userdata", None);
+                try_self_arg!(Err(err));
+            }
+            let state = rawlua.state();
+            // Find absolute "self" index before processing args
+            let index = ffi::lua_absindex(state, -nargs);
+            // Self was at position 1, so we pass 2 here
+            let args = A::from_stack_args(nargs - 1, 2, Some(&name), rawlua);
+
+            match try_self_arg!(rawlua.get_userdata_type_id(index)) {
+                Some(id) if id == TypeId::of::<T>() => {
+                    let ud = try_self_arg!(borrow_userdata_ref::<T>(state, index));
+                    method(rawlua.lua(), &ud, args?)?.push_into_stack_multi(rawlua)
+                }
+                _ => Err(Error::bad_self_argument(&name, Error::UserDataTypeMismatch)),
+            }
+        })
+    }
+
+    fn box_method_mut<M, A, R>(name: &str, method: M) -> Callback<'a>
+    where
+        M: FnMut(&'a Lua, &mut T, A) -> Result<R> + MaybeSend + 'static,
+        A: FromLuaMulti,
+        R: IntoLuaMulti,
+    {
+        let name = get_function_name::<T>(name);
+        macro_rules! try_self_arg {
+            ($res:expr) => {
+                $res.map_err(|err| Error::bad_self_argument(&name, err))?
+            };
+        }
+
+        let method = RefCell::new(method);
+        Box::new(move |rawlua, nargs| unsafe {
+            let mut method = method.try_borrow_mut().map_err(|_| Error::RecursiveMutCallback)?;
+            if nargs == 0 {
+                let err = Error::from_lua_conversion("missing argument", "userdata", None);
+                try_self_arg!(Err(err));
+            }
+            let state = rawlua.state();
+            // Find absolute "self" index before processing args
+            let index = ffi::lua_absindex(state, -nargs);
+            // Self was at position 1, so we pass 2 here
+            let args = A::from_stack_args(nargs - 1, 2, Some(&name), rawlua);
+
+            match try_self_arg!(rawlua.get_userdata_type_id(index)) {
+                Some(id) if id == TypeId::of::<T>() => {
+                    let mut ud = try_self_arg!(borrow_userdata_mut::<T>(state, index));
+                    method(rawlua.lua(), &mut ud, args?)?.push_into_stack_multi(rawlua)
+                }
+                _ => Err(Error::bad_self_argument(&name, Error::UserDataTypeMismatch)),
+            }
+        })
+    }
+
+    #[cfg(feature = "async")]
+    fn box_async_method<M, A, MR, R>(name: &str, method: M) -> AsyncCallback<'a>
+    where
+        M: Fn(&'a Lua, &'a T, A) -> MR + MaybeSend + 'static,
+        A: FromLuaMulti,
+        MR: Future<Output = Result<R>> + 'a,
+        R: IntoLuaMulti,
+    {
+        let name = get_function_name::<T>(name);
+        macro_rules! try_self_arg {
+            ($res:expr) => {
+                match $res {
+                    Ok(res) => res,
+                    Err(err) => return Box::pin(future::ready(Err(Error::bad_self_argument(&name, err)))),
+                }
+            };
+        }
+
+        Box::new(move |rawlua, mut args| unsafe {
+            let this = args
+                .pop_front()
+                .ok_or_else(|| Error::from_lua_conversion("missing argument", "userdata", None));
+            let lua = rawlua.lua();
+            let this = try_self_arg!(AnyUserData::from_lua(try_self_arg!(this), lua));
+            let args = A::from_lua_args(args, 2, Some(&name), lua);
+
+            let (ref_thread, index) = (rawlua.ref_thread(), this.0.index);
+            match try_self_arg!(this.type_id()) {
+                Some(id) if id == TypeId::of::<T>() => {
+                    let ud = try_self_arg!(borrow_userdata_ref::<T>(ref_thread, index));
+                    let args = match args {
+                        Ok(args) => args,
+                        Err(e) => return Box::pin(future::ready(Err(e))),
+                    };
+                    let fut = method(lua, ud.get_ref(), args);
+                    Box::pin(async move { fut.await?.push_into_stack_multi(rawlua) })
+                }
+                _ => {
+                    let err = Error::bad_self_argument(&name, Error::UserDataTypeMismatch);
+                    Box::pin(future::ready(Err(err)))
+                }
+            }
+        })
+    }
+
+    #[cfg(feature = "async")]
+    fn box_async_method_mut<M, A, MR, R>(name: &str, method: M) -> AsyncCallback<'a>
+    where
+        M: Fn(&'a Lua, &'a mut T, A) -> MR + MaybeSend + 'static,
+        A: FromLuaMulti,
+        MR: Future<Output = Result<R>> + 'a,
+        R: IntoLuaMulti,
+    {
+        let name = get_function_name::<T>(name);
+        macro_rules! try_self_arg {
+            ($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, mut args| unsafe {
+            let this = args
+                .pop_front()
+                .ok_or_else(|| Error::from_lua_conversion("missing argument", "userdata", None));
+            let lua = rawlua.lua();
+            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) = (rawlua.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!(borrow_userdata_mut::<T>(ref_thread, index));
+                    let args = match args {
+                        Ok(args) => args,
+                        Err(e) => return Box::pin(future::ready(Err(e))),
+                    };
+                    let fut = method(lua, ud.get_mut(), args);
+                    Box::pin(async move { fut.await?.push_into_stack_multi(rawlua) })
+                }
+                _ => {
+                    let err = Error::bad_self_argument(&name, Error::UserDataTypeMismatch);
+                    Box::pin(future::ready(Err(err)))
+                }
+            }
+        })
+    }
+
+    fn box_function<F, A, R>(name: &str, function: F) -> Callback<'a>
+    where
+        F: Fn(&'a 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<'a>
+    where
+        F: FnMut(&'a 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<'a>
+    where
+        F: Fn(&'a Lua, A) -> FR + MaybeSend + 'static,
+        A: FromLuaMulti,
+        FR: Future<Output = Result<R>> + 'a,
+        R: IntoLuaMulti,
+    {
+        let name = get_function_name::<T>(name);
+        Box::new(move |rawlua, args| unsafe {
+            let lua = rawlua.lua();
+            let args = match A::from_lua_args(args, 1, Some(&name), lua) {
+                Ok(args) => args,
+                Err(e) => return Box::pin(future::ready(Err(e))),
+            };
+            let fut = function(lua, args);
+            Box::pin(async move { fut.await?.push_into_stack_multi(rawlua) })
+        })
+    }
+
+    pub(crate) fn check_meta_field<V>(lua: &Lua, name: &str, value: V) -> Result<Value>
+    where
+        V: IntoLua,
+    {
+        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<'a, T: 'static> UserDataFields<'a, T> for UserDataRegistry<'a, T> {
+    fn add_field<V>(&mut self, name: impl ToString, value: V)
+    where
+        V: IntoLua + Clone + 'static,
+    {
+        let name = name.to_string();
+        let callback = Box::new(move |lua, _| unsafe { value.clone().push_into_stack_multi(lua) });
+        self.fields.push((name, callback));
+    }
+
+    fn add_field_method_get<M, R>(&mut self, name: impl ToString, method: M)
+    where
+        M: Fn(&'a 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(&'a 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(&'a 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(&'a 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 + Clone + 'static,
+    {
+        let name = name.to_string();
+        self.meta_fields.push((
+            name.clone(),
+            Box::new(move |lua, _| unsafe {
+                Self::check_meta_field(lua.lua(), &name, value.clone())?.push_into_stack_multi(lua)
+            }),
+        ));
+    }
+
+    fn add_meta_field_with<F, R>(&mut self, name: impl ToString, f: F)
+    where
+        F: Fn(&'a Lua) -> Result<R> + MaybeSend + '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_multi(rawlua)
+            }),
+        ));
+    }
+}
+
+impl<'a, T: 'static> UserDataMethods<'a, T> for UserDataRegistry<'a, T> {
+    fn add_method<M, A, R>(&mut self, name: impl ToString, method: M)
+    where
+        M: Fn(&'a 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(&'a 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(&'a Lua, &'a T, A) -> MR + MaybeSend + 'static,
+        A: FromLuaMulti,
+        MR: Future<Output = Result<R>> + 'a,
+        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(&'a Lua, &'a mut T, A) -> MR + MaybeSend + 'static,
+        A: FromLuaMulti,
+        MR: Future<Output = Result<R>> + 'a,
+        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(&'a 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(&'a 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(&'a Lua, A) -> FR + MaybeSend + 'static,
+        A: FromLuaMulti,
+        FR: Future<Output = Result<R>> + 'a,
+        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(&'a 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(&'a 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(&'a Lua, &'a T, A) -> MR + MaybeSend + 'static,
+        A: FromLuaMulti,
+        MR: Future<Output = Result<R>> + 'a,
+        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(&'a Lua, &'a mut T, A) -> MR + MaybeSend + 'static,
+        A: FromLuaMulti,
+        MR: Future<Output = Result<R>> + 'a,
+        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(&'a 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(&'a 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(&'a Lua, A) -> FR + MaybeSend + 'static,
+        A: FromLuaMulti,
+        FR: Future<Output = Result<R>> + 'a,
+        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_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/mod.rs

@@ -1,45 +1,43 @@
-use std::any::{Any, TypeId};
 use std::borrow::Cow;
 use std::ffi::CStr;
-use std::fmt::Write;
-use std::mem::MaybeUninit;
-use std::os::raw::{c_char, c_int, c_void};
-use std::panic::{catch_unwind, resume_unwind, AssertUnwindSafe};
-use std::sync::Arc;
+use std::os::raw::{c_char, c_int};
 use std::{ptr, slice, str};
 
-use once_cell::sync::Lazy;
-use rustc_hash::FxHashMap;
-
 use crate::error::{Error, Result};
-use crate::memory::MemoryState;
 
+pub(crate) use error::{
+    error_traceback, error_traceback_thread, init_error_registry, pop_error, protect_lua_call,
+    protect_lua_closure, WrappedFailure,
+};
 pub(crate) use short_names::short_type_name;
+pub(crate) use types::TypeKey;
+pub(crate) use userdata::{
+    get_destructed_userdata_metatable, get_internal_metatable, get_internal_userdata, get_userdata,
+    init_internal_metatable, init_userdata_metatable, push_internal_userdata, take_userdata,
+    DESTRUCTED_USERDATA_METATABLE,
+};
 
-static METATABLE_CACHE: Lazy<FxHashMap<TypeId, u8>> = Lazy::new(|| {
-    let mut map = FxHashMap::with_capacity_and_hasher(32, Default::default());
-    crate::lua::init_metatable_cache(&mut map);
-    map.insert(TypeId::of::<WrappedFailure>(), 0);
-    map.insert(TypeId::of::<String>(), 0);
-    map
-});
+#[cfg(not(feature = "lua54"))]
+pub(crate) use userdata::push_userdata;
+#[cfg(feature = "lua54")]
+pub(crate) use userdata::push_userdata_uv;
+
+#[cfg(not(feature = "luau"))]
+pub(crate) use userdata::userdata_destructor;
 
 // Checks that Lua has enough free stack space for future stack operations. On failure, this will
 // panic with an internal error message.
 #[inline]
-pub unsafe fn assert_stack(state: *mut ffi::lua_State, amount: c_int) {
+pub(crate) unsafe fn assert_stack(state: *mut ffi::lua_State, amount: c_int) {
     // TODO: This should only be triggered when there is a logic error in `mlua`. In the future,
     // when there is a way to be confident about stack safety and test it, this could be enabled
     // only when `cfg!(debug_assertions)` is true.
-    mlua_assert!(
-        ffi::lua_checkstack(state, amount) != 0,
-        "out of stack space"
-    );
+    mlua_assert!(ffi::lua_checkstack(state, amount) != 0, "out of stack space");
 }
 
 // Checks that Lua has enough free stack space and returns `Error::StackError` on failure.
 #[inline]
-pub unsafe fn check_stack(state: *mut ffi::lua_State, amount: c_int) -> Result<()> {
+pub(crate) unsafe fn check_stack(state: *mut ffi::lua_State, amount: c_int) -> Result<()> {
     if ffi::lua_checkstack(state, amount) == 0 {
         Err(Error::StackError)
     } else {
@@ -47,7 +45,7 @@ pub unsafe fn check_stack(state: *mut ffi::lua_State, amount: c_int) -> Result<(
     }
 }
 
-pub struct StackGuard {
+pub(crate) struct StackGuard {
     state: *mut ffi::lua_State,
     top: c_int,
 }
@@ -57,7 +55,7 @@ impl StackGuard {
     // stack size and drop any extra elements. If the stack size at the end is *smaller* than at
     // the beginning, this is considered a fatal logic error and will result in a panic.
     #[inline]
-    pub unsafe fn new(state: *mut ffi::lua_State) -> StackGuard {
+    pub(crate) unsafe fn new(state: *mut ffi::lua_State) -> StackGuard {
         StackGuard {
             state,
             top: ffi::lua_gettop(state),
@@ -65,7 +63,8 @@ impl StackGuard {
     }
 
     // Same as `new()`, but allows specifying the expected stack size at the end of the scope.
-    pub const fn with_top(state: *mut ffi::lua_State, top: c_int) -> StackGuard {
+    #[inline]
+    pub(crate) fn with_top(state: *mut ffi::lua_State, top: c_int) -> StackGuard {
         StackGuard { state, top }
     }
 }
@@ -84,164 +83,9 @@ impl Drop for StackGuard {
     }
 }
 
-// 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 lonjmping,
-// should not contain any values that implements Drop.
-// Internally uses 2 extra stack spaces, and does not call checkstack.
-pub 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 lonjmping, should not contain any values that implements Drop.
-// Internally uses 3 extra stack spaces, and does not call checkstack.
-pub 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))
-    }
-}
-
-// 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 WrappedPanic, this will continue the panic.
-//   2) If the error on the top of the stack is actually a WrappedError, just returns it.
-//   3) Otherwise, interprets the error as the appropriate lua error.
-// Uses 2 stack spaces, does not call checkstack.
-pub 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_gc_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"),
-            }
-        }
-    }
-}
-
 // Uses 3 (or 1 if unprotected) stack spaces, does not call checkstack.
 #[inline(always)]
-pub unsafe fn push_string(state: *mut ffi::lua_State, s: &[u8], protect: bool) -> Result<()> {
+pub(crate) unsafe fn push_string(state: *mut ffi::lua_State, s: &[u8], protect: bool) -> Result<()> {
     // Always use protected mode if the string is too long
     if protect || s.len() > (1 << 30) {
         protect_lua!(state, 0, 1, |state| {
@@ -256,7 +100,7 @@ pub unsafe fn push_string(state: *mut ffi::lua_State, s: &[u8], protect: bool) -
 // Uses 3 stack spaces (when protect), does not call checkstack.
 #[cfg(feature = "luau")]
 #[inline(always)]
-pub unsafe fn push_buffer(state: *mut ffi::lua_State, b: &[u8], protect: bool) -> Result<()> {
+pub(crate) unsafe fn push_buffer(state: *mut ffi::lua_State, b: &[u8], protect: bool) -> Result<()> {
     let data = if protect {
         protect_lua!(state, 0, 1, |state| ffi::lua_newbuffer(state, b.len()))?
     } else {
@@ -269,7 +113,7 @@ pub unsafe fn push_buffer(state: *mut ffi::lua_State, b: &[u8], protect: bool) -
 
 // Uses 3 stack spaces, does not call checkstack.
 #[inline]
-pub unsafe fn push_table(
+pub(crate) unsafe fn push_table(
     state: *mut ffi::lua_State,
     narr: usize,
     nrec: usize,
@@ -286,7 +130,7 @@ pub unsafe fn push_table(
 }
 
 // Uses 4 stack spaces, does not call checkstack.
-pub unsafe fn rawset_field(state: *mut ffi::lua_State, table: c_int, field: &str) -> Result<()> {
+pub(crate) unsafe fn rawset_field(state: *mut ffi::lua_State, table: c_int, field: &str) -> Result<()> {
     ffi::lua_pushvalue(state, table);
     protect_lua!(state, 2, 0, |state| {
         ffi::lua_pushlstring(state, field.as_ptr() as *const c_char, field.len());
@@ -295,441 +139,8 @@ pub unsafe fn rawset_field(state: *mut ffi::lua_State, table: c_int, field: &str
     })
 }
 
-// Internally uses 3 stack spaces, does not call checkstack.
-#[inline]
-pub 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 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 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 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)
-}
-
-// Pushes the userdata and attaches a metatable with __gc method.
-// Internally uses 3 stack spaces, does not call checkstack.
-pub unsafe fn push_gc_userdata<T: Any>(
-    state: *mut ffi::lua_State,
-    t: T,
-    protect: bool,
-) -> Result<()> {
-    push_userdata(state, t, protect)?;
-    get_gc_metatable::<T>(state);
-    ffi::lua_setmetatable(state, -2);
-    Ok(())
-}
-
-// Uses 2 stack spaces, does not call checkstack
-pub unsafe fn get_gc_userdata<T: Any>(
-    state: *mut ffi::lua_State,
-    index: c_int,
-    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 !mt_ptr.is_null() {
-        let ud_mt_ptr = ffi::lua_topointer(state, -1);
-        ffi::lua_pop(state, 1);
-        if !ptr::eq(ud_mt_ptr, mt_ptr) {
-            return ptr::null_mut();
-        }
-    } else {
-        get_gc_metatable::<T>(state);
-        let res = ffi::lua_rawequal(state, -1, -2);
-        ffi::lua_pop(state, 2);
-        if res == 0 {
-            return ptr::null_mut();
-        }
-    }
-    ud
-}
-
-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);
-    })
-}
-
-pub 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);
-    })
-}
-
-// 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 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(())
-}
-
-#[cfg(not(feature = "luau"))]
-pub 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
-}
-
-// 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.
-pub 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_gc_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_gc_metatable::<WrappedFailure>(state);
-            ffi::lua_setmetatable(state, -2);
-            ffi::lua_error(state)
-        }
-    }
-}
-
-pub 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_gc_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 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_gc_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);
-        }
-    }
-}
-
 // A variant of `pcall` that does not allow Lua to catch Rust panics from `callback_error`.
-pub unsafe extern "C-unwind" fn safe_pcall(state: *mut ffi::lua_State) -> c_int {
+pub(crate) unsafe extern "C-unwind" fn safe_pcall(state: *mut ffi::lua_State) -> c_int {
     ffi::luaL_checkstack(state, 2, ptr::null());
 
     let top = ffi::lua_gettop(state);
@@ -743,9 +154,8 @@ pub unsafe extern "C-unwind" fn safe_pcall(state: *mut ffi::lua_State) -> c_int
         ffi::lua_insert(state, 1);
         ffi::lua_gettop(state)
     } else {
-        if let Some(WrappedFailure::Panic(_)) =
-            get_gc_userdata::<WrappedFailure>(state, -1, ptr::null()).as_ref()
-        {
+        let wf_ud = get_internal_userdata::<WrappedFailure>(state, -1, ptr::null());
+        if let Some(WrappedFailure::Panic(_)) = wf_ud.as_ref() {
             ffi::lua_error(state);
         }
         ffi::lua_pushboolean(state, 0);
@@ -755,13 +165,12 @@ pub unsafe extern "C-unwind" fn safe_pcall(state: *mut ffi::lua_State) -> c_int
 }
 
 // A variant of `xpcall` that does not allow Lua to catch Rust panics from `callback_error`.
-pub unsafe extern "C-unwind" fn safe_xpcall(state: *mut ffi::lua_State) -> c_int {
+pub(crate) unsafe extern "C-unwind" fn safe_xpcall(state: *mut ffi::lua_State) -> c_int {
     unsafe extern "C-unwind" fn xpcall_msgh(state: *mut ffi::lua_State) -> c_int {
         ffi::luaL_checkstack(state, 2, ptr::null());
 
-        if let Some(WrappedFailure::Panic(_)) =
-            get_gc_userdata::<WrappedFailure>(state, -1, ptr::null()).as_ref()
-        {
+        let wf_ud = get_internal_userdata::<WrappedFailure>(state, -1, ptr::null());
+        if let Some(WrappedFailure::Panic(_)) = wf_ud.as_ref() {
             1
         } else {
             ffi::lua_pushvalue(state, ffi::lua_upvalueindex(1));
@@ -789,9 +198,8 @@ pub unsafe extern "C-unwind" fn safe_xpcall(state: *mut ffi::lua_State) -> c_int
         ffi::lua_insert(state, 2);
         ffi::lua_gettop(state) - 1
     } else {
-        if let Some(WrappedFailure::Panic(_)) =
-            get_gc_userdata::<WrappedFailure>(state, -1, ptr::null()).as_ref()
-        {
+        let wf_ud = get_internal_userdata::<WrappedFailure>(state, -1, ptr::null());
+        if let Some(WrappedFailure::Panic(_)) = wf_ud.as_ref() {
             ffi::lua_error(state);
         }
         ffi::lua_pushboolean(state, 0);
@@ -802,7 +210,7 @@ pub unsafe extern "C-unwind" fn safe_xpcall(state: *mut ffi::lua_State) -> c_int
 
 // Returns Lua main thread for Lua >= 5.2 or checks that the passed thread is main for Lua 5.1.
 // Does not call lua_checkstack, uses 1 stack space.
-pub unsafe fn get_main_state(state: *mut ffi::lua_State) -> Option<*mut ffi::lua_State> {
+pub(crate) unsafe fn get_main_state(state: *mut ffi::lua_State) -> Option<*mut ffi::lua_State> {
     #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     {
         ffi::lua_rawgeti(state, ffi::LUA_REGISTRYINDEX, ffi::LUA_RIDX_MAINTHREAD);
@@ -825,198 +233,6 @@ pub unsafe fn get_main_state(state: *mut ffi::lua_State) -> Option<*mut ffi::lua
     Some(ffi::lua_mainthread(state))
 }
 
-// Initialize the internal (with __gc method) metatable for a type T.
-// Uses 6 stack spaces and calls checkstack.
-pub unsafe fn init_gc_metatable<T: Any>(
-    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)?;
-    }
-
-    let type_id = TypeId::of::<T>();
-    let ref_addr = &METATABLE_CACHE[&type_id] as *const u8;
-    protect_lua!(state, 1, 0, |state| {
-        ffi::lua_rawsetp(state, ffi::LUA_REGISTRYINDEX, ref_addr as *const c_void);
-    })?;
-
-    Ok(())
-}
-
-pub unsafe fn get_gc_metatable<T: Any>(state: *mut ffi::lua_State) {
-    let type_id = TypeId::of::<T>();
-    let ref_addr =
-        mlua_expect!(METATABLE_CACHE.get(&type_id), "gc metatable does not exist") as *const u8;
-    ffi::lua_rawgetp(state, ffi::LUA_REGISTRYINDEX, ref_addr as *const c_void);
-}
-
-// Initialize the error, panic, and destructed userdata metatables.
-pub unsafe fn init_error_registry(state: *mut ffi::lua_State) -> Result<()> {
-    check_stack(state, 7)?;
-
-    // Create error and panic metatables
-
-    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_gc_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_gc_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_gc_metatable::<String>(state, None)?;
-    push_gc_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(())
-}
-
-pub(crate) enum WrappedFailure {
-    None,
-    Error(Error),
-    Panic(Option<Box<dyn Any + Send + 'static>>),
-}
-
-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
-    }
-}
-
 // Converts the given lua value to a string in a reasonable format without causing a Lua error or
 // panicking.
 pub(crate) unsafe fn to_string(state: *mut ffi::lua_State, index: c_int) -> String {
@@ -1065,11 +281,6 @@ pub(crate) unsafe fn to_string(state: *mut ffi::lua_State, index: c_int) -> Stri
     }
 }
 
-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);
-}
-
 pub(crate) unsafe fn ptr_to_str<'a>(input: *const c_char) -> Option<&'a str> {
     if input.is_null() {
         return None;
@@ -1091,9 +302,7 @@ pub(crate) fn linenumber_to_usize(n: c_int) -> Option<usize> {
     }
 }
 
-static DESTRUCTED_USERDATA_METATABLE: u8 = 0;
-static ERROR_PRINT_BUFFER_KEY: u8 = 0;
-static USERDATA_METATABLE_INDEX: u8 = 0;
-static USERDATA_METATABLE_NEWINDEX: u8 = 0;
-
+mod error;
 mod short_names;
+mod types;
+mod userdata;

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<'static> {
+    #[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<'static> {
+    #[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

@@ -1,15 +1,23 @@
-use std::borrow::Cow;
 use std::cmp::Ordering;
-use std::collections::HashSet;
-use std::iter;
-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;
 
+use crate::error::{Error, Result};
+use crate::function::Function;
+use crate::state::{Lua, RawLua};
+use crate::string::{BorrowedStr, String};
+use crate::table::Table;
+use crate::thread::Thread;
+use crate::types::{Integer, LightUserData, Number, SubtypeId};
+use crate::userdata::AnyUserData;
+use crate::util::{check_stack, StackGuard};
+
 #[cfg(feature = "serialize")]
 use {
     crate::table::SerializableTable,
@@ -18,21 +26,11 @@ use {
     std::{cell::RefCell, 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::table::Table;
-use crate::thread::Thread;
-use crate::types::{Integer, LightUserData, Number, SubtypeId};
-use crate::userdata::AnyUserData;
-use crate::util::{check_stack, StackGuard};
-
 /// 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 +50,27 @@ 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 +115,8 @@ 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 +135,8 @@ 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 +152,16 @@ 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()),
         }
@@ -329,19 +329,20 @@ 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())
     }
 
@@ -441,7 +442,7 @@ 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)
     }
 
@@ -477,7 +478,7 @@ 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
@@ -523,7 +524,7 @@ 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());
@@ -546,7 +547,7 @@ 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,
@@ -568,7 +569,7 @@ 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
@@ -578,15 +579,15 @@ 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)
@@ -594,10 +595,10 @@ 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 {
@@ -649,7 +650,7 @@ 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,
@@ -688,9 +689,9 @@ 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.
     ///
@@ -698,15 +699,15 @@ 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).
     ///
@@ -714,7 +715,7 @@ 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,
@@ -726,19 +727,14 @@ 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), 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,
@@ -750,191 +746,136 @@ 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>,
+pub struct MultiValue {
+    deque: VecDeque<Value>,
+    // FIXME
+    // lua: Option<&'static Lua>,
 }
 
-impl Drop for MultiValue<'_> {
+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);
-        }
+        // FIXME
+        // if let Some(lua) = self.lua {
+        //     let vec = mem::take(&mut self.deque);
+        //     lua.push_multivalue_to_pool(vec);
+        // }
     }
 }
 
-impl<'lua> MultiValue<'lua> {
+impl Default for MultiValue {
+    #[inline]
+    fn default() -> MultiValue {
+        MultiValue::new()
+    }
+}
+
+impl Deref for MultiValue {
+    type Target = VecDeque<Value>;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &self.deque
+    }
+}
+
+impl DerefMut for MultiValue {
+    #[inline]
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.deque
+    }
+}
+
+impl MultiValue {
     /// Creates an empty `MultiValue` containing no values.
-    pub const fn new() -> MultiValue<'lua> {
+    pub const fn new() -> MultiValue {
         MultiValue {
-            vec: Vec::new(),
-            lua: None,
+            deque: VecDeque::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));
+    pub(crate) fn with_lua_and_capacity(_lua: &Lua, capacity: usize) -> MultiValue {
+        // FIXME
+        // let deque = lua
+        //     .pop_multivalue_from_pool()
+        //     .map(|mut deque| {
+        //         if capacity > 0 {
+        //             deque.reserve(capacity);
+        //         }
+        //         deque
+        //     })
+        //     .unwrap_or_else(|| VecDeque::with_capacity(capacity));
+        let deque = VecDeque::with_capacity(capacity);
         MultiValue {
-            vec,
-            lua: Some(lua),
+            deque,
+            // lua: Some(lua),
+        }
+    }
+
+    #[inline]
+    pub(crate) fn extend_from_values(&mut self, iter: impl IntoIterator<Item = Result<Value>>) -> Result<()> {
+        for value in iter {
+            self.push_back(value?);
+        }
+        Ok(())
+    }
+}
+
+impl FromIterator<Value> for MultiValue {
+    #[inline]
+    fn from_iter<I: IntoIterator<Item = Value>>(iter: I) -> Self {
+        let deque = VecDeque::from_iter(iter);
+        MultiValue {
+            deque,
+            // lua: None,
         }
     }
 }
 
-impl<'lua> Default for MultiValue<'lua> {
-    #[inline]
-    fn default() -> MultiValue<'lua> {
-        MultiValue::new()
-    }
-}
-
-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.deque);
         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.deque.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)
@@ -945,14 +886,14 @@ 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.
     ///
@@ -960,12 +901,7 @@ 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)
     }
@@ -973,27 +909,22 @@ 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_lua_and_capacity(lua.lua(), nvals as usize);
+        for idx in 0..nvals {
+            values.push_back(lua.stack_value(-nvals + idx));
         }
         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)
     }
@@ -1003,6 +934,13 @@ 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);
 }

tests/async.rs

@@ -6,8 +6,8 @@ use std::time::Duration;
 use futures_util::stream::TryStreamExt;
 
 use mlua::{
-    AnyUserDataExt, Error, Function, Lua, LuaOptions, MultiValue, Result, StdLib, Table, TableExt,
-    UserData, UserDataMethods, Value,
+    AnyUserDataExt, Error, Function, Lua, LuaOptions, MultiValue, Result, StdLib, Table, TableExt, UserData,
+    UserDataMethods, Value,
 };
 
 #[cfg(not(target_arch = "wasm32"))]
@@ -25,8 +25,7 @@ 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?;
@@ -75,9 +74,7 @@ async fn test_async_call() -> Result<()> {
 
     match hello.call::<_, ()>("alex") {
         Err(Error::RuntimeError(_)) => {}
-        _ => panic!(
-            "non-async executing async function must fail on the yield stage with RuntimeError"
-        ),
+        _ => panic!("non-async executing async function must fail on the yield stage with RuntimeError"),
     };
 
     assert_eq!(hello.call_async::<_, String>("alex").await?, "hello, alex!");
@@ -342,15 +339,9 @@ async fn test_async_table() -> Result<()> {
     })?;
     table.set("sleep", sleep)?;
 
-    assert_eq!(
-        table.call_async_method::<_, i64>("get_value", ()).await?,
-        10
-    );
+    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?, 15);
     assert_eq!(
         table.call_async_function::<_, String>("sleep", 7).await?,
         "elapsed:7ms"
@@ -386,7 +377,7 @@ 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<'a, M: UserDataMethods<'a, Self>>(methods: &mut M) {
             methods.add_async_method("get_value", |_, data, ()| async move {
                 sleep_ms(10).await;
                 Ok(data.0)
@@ -411,17 +402,14 @@ 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(
@@ -488,7 +476,7 @@ 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<'a, M: UserDataMethods<'a, Self>>(methods: &mut M) {
             methods.add_meta_method("__tostring", |_, _this, ()| Ok("myuserdata error"))
         }
     }
@@ -507,24 +495,6 @@ 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();

tests/chunk.rs

@@ -1,5 +1,4 @@
-use std::fs;
-use std::io;
+use std::{fs, io};
 
 use mlua::{Lua, Result};
 

tests/conversion.rs

@@ -5,8 +5,7 @@ use std::ffi::{CStr, CString};
 use bstr::BString;
 use maplit::{btreemap, btreeset, hashmap, hashset};
 use mlua::{
-    AnyUserData, Error, Function, IntoLua, Lua, RegistryKey, Result, Table, Thread, UserDataRef,
-    Value,
+    AnyUserData, Error, Function, IntoLua, Lua, RegistryKey, Result, Table, Thread, UserDataRef, Value,
 };
 
 #[test]
@@ -43,35 +42,6 @@ fn test_string_into_lua() -> Result<()> {
     Ok(())
 }
 
-#[cfg(all(feature = "unstable", not(feature = "send")))]
-#[test]
-fn test_owned_string_into_lua() -> Result<()> {
-    let lua = Lua::new();
-
-    // Direct conversion
-    let s = lua.create_string("hello, world")?.into_owned();
-    let s2 = (&s).into_lua(&lua)?;
-    assert_eq!(s.to_ref(), *s2.as_string().unwrap());
-
-    // Push into stack
-    let table = lua.create_table()?;
-    table.set("s", &s)?;
-    assert_eq!(s.to_ref(), table.get::<_, String>("s")?);
-
-    Ok(())
-}
-
-#[cfg(all(feature = "unstable", not(feature = "send")))]
-#[test]
-fn test_owned_string_from_lua() -> Result<()> {
-    let lua = Lua::new();
-
-    let s = lua.unpack::<mlua::OwnedString>(lua.pack("hello, world")?)?;
-    assert_eq!(s.to_ref(), "hello, world");
-
-    Ok(())
-}
-
 #[test]
 fn test_table_into_lua() -> Result<()> {
     let lua = Lua::new();
@@ -89,24 +59,6 @@ fn test_table_into_lua() -> Result<()> {
     Ok(())
 }
 
-#[cfg(all(feature = "unstable", not(feature = "send")))]
-#[test]
-fn test_owned_table_into_lua() -> Result<()> {
-    let lua = Lua::new();
-
-    // Direct conversion
-    let t = lua.create_table()?.into_owned();
-    let t2 = (&t).into_lua(&lua)?;
-    assert_eq!(t.to_ref(), *t2.as_table().unwrap());
-
-    // Push into stack
-    let f = lua.create_function(|_, (t, s): (Table, String)| t.set("s", s))?;
-    f.call((&t, "hello"))?;
-    assert_eq!("hello", t.to_ref().get::<_, String>("s")?);
-
-    Ok(())
-}
-
 #[test]
 fn test_function_into_lua() -> Result<()> {
     let lua = Lua::new();
@@ -124,26 +76,6 @@ fn test_function_into_lua() -> Result<()> {
     Ok(())
 }
 
-#[cfg(all(feature = "unstable", not(feature = "send")))]
-#[test]
-fn test_owned_function_into_lua() -> Result<()> {
-    let lua = Lua::new();
-
-    // Direct conversion
-    let f = lua
-        .create_function(|_, ()| Ok::<_, Error>(()))?
-        .into_owned();
-    let f2 = (&f).into_lua(&lua)?;
-    assert_eq!(f.to_ref(), *f2.as_function().unwrap());
-
-    // Push into stack
-    let table = lua.create_table()?;
-    table.set("f", &f)?;
-    assert_eq!(f.to_ref(), table.get::<_, Function>("f")?);
-
-    Ok(())
-}
-
 #[test]
 fn test_thread_into_lua() -> Result<()> {
     let lua = Lua::new();
@@ -162,36 +94,6 @@ fn test_thread_into_lua() -> Result<()> {
     Ok(())
 }
 
-#[cfg(all(feature = "unstable", not(feature = "send")))]
-#[test]
-fn test_owned_thread_into_lua() -> Result<()> {
-    let lua = Lua::new();
-
-    // Direct conversion
-    let f = lua.create_function(|_, ()| Ok::<_, Error>(()))?;
-    let th = lua.create_thread(f)?.into_owned();
-    let th2 = (&th).into_lua(&lua)?;
-    assert_eq!(&th.to_ref(), th2.as_thread().unwrap());
-
-    // Push into stack
-    let table = lua.create_table()?;
-    table.set("th", &th)?;
-    assert_eq!(th.to_ref(), table.get::<_, Thread>("th")?);
-
-    Ok(())
-}
-
-#[cfg(all(feature = "unstable", not(feature = "send")))]
-#[test]
-fn test_owned_thread_from_lua() -> Result<()> {
-    let lua = Lua::new();
-
-    let th = lua.unpack::<mlua::OwnedThread>(Value::Thread(lua.current_thread()))?;
-    assert_eq!(th.to_ref(), lua.current_thread());
-
-    Ok(())
-}
-
 #[test]
 fn test_anyuserdata_into_lua() -> Result<()> {
     let lua = Lua::new();
@@ -210,25 +112,6 @@ fn test_anyuserdata_into_lua() -> Result<()> {
     Ok(())
 }
 
-#[cfg(all(feature = "unstable", not(feature = "send")))]
-#[test]
-fn test_owned_anyuserdata_into_lua() -> Result<()> {
-    let lua = Lua::new();
-
-    // Direct conversion
-    let ud = lua.create_any_userdata(String::from("hello"))?.into_owned();
-    let ud2 = (&ud).into_lua(&lua)?;
-    assert_eq!(ud.to_ref(), *ud2.as_userdata().unwrap());
-
-    // Push into stack
-    let table = lua.create_table()?;
-    table.set("ud", &ud)?;
-    assert_eq!(ud.to_ref(), table.get::<_, AnyUserData>("ud")?);
-    assert_eq!("hello", *table.get::<_, UserDataRef<String>>("ud")?);
-
-    Ok(())
-}
-
 #[test]
 fn test_registry_value_into_lua() -> Result<()> {
     let lua = Lua::new();
@@ -238,7 +121,7 @@ fn test_registry_value_into_lua() -> Result<()> {
     let r = lua.create_registry_value(&s)?;
     let value1 = lua.pack(&r)?;
     let value2 = lua.pack(r)?;
-    assert_eq!(value1.as_str(), Some("hello, world"));
+    assert_eq!(value1.as_str().as_deref(), Some("hello, world"));
     assert_eq!(value2.to_pointer(), value2.to_pointer());
 
     // Push into stack
@@ -258,10 +141,7 @@ fn test_registry_value_into_lua() -> Result<()> {
     // Check non-owned registry key
     let lua2 = Lua::new();
     let r2 = lua2.create_registry_value("abc")?;
-    assert!(matches!(
-        f.call::<_, ()>(&r2),
-        Err(Error::MismatchedRegistryKey)
-    ));
+    assert!(matches!(f.call::<_, ()>(&r2), Err(Error::MismatchedRegistryKey)));
 
     Ok(())
 }

tests/error.rs

@@ -6,9 +6,8 @@ use mlua::{Error, ErrorContext, Lua, Result};
 fn test_error_context() -> Result<()> {
     let lua = Lua::new();
 
-    let func = lua.create_function(|_, ()| {
-        Err::<(), _>(Error::runtime("runtime error")).context("some context")
-    })?;
+    let func =
+        lua.create_function(|_, ()| Err::<(), _>(Error::runtime("runtime error")).context("some context"))?;
     lua.globals().set("func", func)?;
 
     let msg = lua
@@ -33,12 +32,9 @@ fn test_error_context() -> Result<()> {
 
     // Rewrite context message and test `downcast_ref`
     let func3 = lua.create_function(|_, ()| {
-        Err::<(), _>(Error::external(io::Error::new(
-            io::ErrorKind::Other,
-            "other",
-        )))
-        .context("some context")
-        .context("some new context")
+        Err::<(), _>(Error::external(io::Error::new(io::ErrorKind::Other, "other")))
+            .context("some context")
+            .context("some new context")
     })?;
     let res = func3.call::<_, ()>(()).err().unwrap();
     let Error::CallbackError { cause, .. } = &res else {

tests/function.rs

@@ -43,10 +43,7 @@ fn test_bind() -> Result<()> {
     concat = concat.bind("bar")?;
     concat = concat.bind(("baz", "baf"))?;
     assert_eq!(concat.call::<_, String>(())?, "foobarbazbaf");
-    assert_eq!(
-        concat.call::<_, String>(("hi", "wut"))?,
-        "foobarbazbafhiwut"
-    );
+    assert_eq!(concat.call::<_, String>(("hi", "wut"))?, "foobarbazbafhiwut");
 
     let mut concat2 = globals.get::<_, Function>("concat")?;
     concat2 = concat2.bind(())?;
@@ -271,8 +268,7 @@ fn test_function_wrap() -> Result<()> {
 
     let lua = Lua::new();
 
-    lua.globals()
-        .set("f", Function::wrap(|_, s: String| Ok(s)))?;
+    lua.globals().set("f", Function::wrap(|_, s: String| Ok(s)))?;
     lua.load(r#"assert(f("hello") == "hello")"#).exec().unwrap();
 
     let mut _i = false;
@@ -296,45 +292,3 @@ fn test_function_wrap() -> Result<()> {
 
     Ok(())
 }
-
-#[cfg(all(feature = "unstable", not(feature = "send")))]
-#[test]
-fn test_owned_function() -> Result<()> {
-    let lua = Lua::new();
-
-    let f = lua
-        .create_function(|_, ()| Ok("hello, world!"))?
-        .into_owned();
-    drop(lua);
-
-    // We still should be able to call the function despite Lua is dropped
-    let s = f.call::<_, String>(())?;
-    assert_eq!(s.to_string_lossy(), "hello, world!");
-
-    Ok(())
-}
-
-#[cfg(all(feature = "unstable", not(feature = "send")))]
-#[test]
-fn test_owned_function_drop() -> Result<()> {
-    let rc = std::sync::Arc::new(());
-
-    {
-        let lua = Lua::new();
-
-        lua.set_app_data(rc.clone());
-
-        let f1 = lua
-            .create_function(|_, ()| Ok("hello, world!"))?
-            .into_owned();
-        let f2 =
-            lua.create_function(move |_, ()| f1.to_ref().call::<_, std::string::String>(()))?;
-        assert_eq!(f2.call::<_, String>(())?.to_string_lossy(), "hello, world!");
-    }
-
-    // Check that Lua is properly destroyed
-    // It works because we collect garbage when Lua goes out of scope
-    assert_eq!(std::sync::Arc::strong_count(&rc), 1);
-
-    Ok(())
-}

tests/hooks.rs

@@ -75,15 +75,9 @@ fn test_function_calls() -> Result<()> {
 
     let output = output.lock().unwrap();
     if cfg!(feature = "luajit") && lua.load("jit.version_num").eval::<i64>()? >= 20100 {
-        assert_eq!(
-            *output,
-            vec![(None, "main"), (Some("len".to_string()), "Lua")]
-        );
+        assert_eq!(*output, vec![(None, "main"), (Some("len".to_string()), "Lua")]);
     } else {
-        assert_eq!(
-            *output,
-            vec![(None, "main"), (Some("len".to_string()), "C")]
-        );
+        assert_eq!(*output, vec![(None, "main"), (Some("len".to_string()), "C")]);
     }
 
     Ok(())
@@ -97,10 +91,7 @@ fn test_error_within_hook() -> Result<()> {
         Err(Error::runtime("Something happened in there!"))
     });
 
-    let err = lua
-        .load("x = 1")
-        .exec()
-        .expect_err("panic didn't propagate");
+    let err = lua.load("x = 1").exec().expect_err("panic didn't propagate");
 
     match err {
         Error::CallbackError { cause, .. } => match cause.deref() {
@@ -153,14 +144,9 @@ fn test_limit_execution_instructions() -> Result<()> {
 fn test_hook_removal() -> Result<()> {
     let lua = Lua::new();
 
-    lua.set_hook(
-        HookTriggers::new().every_nth_instruction(1),
-        |_lua, _debug| {
-            Err(Error::runtime(
-                "this hook should've been removed by this time",
-            ))
-        },
-    );
+    lua.set_hook(HookTriggers::new().every_nth_instruction(1), |_lua, _debug| {
+        Err(Error::runtime("this hook should've been removed by this time"))
+    });
 
     assert!(lua.load("local x = 1").exec().is_err());
     lua.remove_hook();
@@ -189,9 +175,10 @@ fn test_hook_swap_within_hook() -> Result<()> {
             .set_hook(HookTriggers::EVERY_LINE, move |lua, _debug| {
                 lua.globals().set("ok", 1i64)?;
                 TL_LUA.with(|tl| {
-                    tl.borrow().as_ref().unwrap().set_hook(
-                        HookTriggers::EVERY_LINE,
-                        move |lua, _debug| {
+                    tl.borrow()
+                        .as_ref()
+                        .unwrap()
+                        .set_hook(HookTriggers::EVERY_LINE, move |lua, _debug| {
                             lua.load(
                                 r#"
                                     if ok ~= nil then
@@ -205,8 +192,7 @@ fn test_hook_swap_within_hook() -> Result<()> {
                                 tl.borrow().as_ref().unwrap().remove_hook();
                             });
                             Ok(())
-                        },
-                    )
+                        })
                 });
                 Ok(())
             })

tests/luau.rs

@@ -7,17 +7,14 @@ use std::sync::atomic::{AtomicU64, Ordering};
 use std::sync::Arc;
 
 use mlua::{
-    Compiler, CoverageInfo, Error, Lua, LuaOptions, Result, StdLib, Table, ThreadStatus, Value,
-    Vector, VmState,
+    Compiler, CoverageInfo, Error, Lua, LuaOptions, Result, StdLib, Table, ThreadStatus, Value, Vector,
+    VmState,
 };
 
 #[test]
 fn test_version() -> Result<()> {
     let lua = Lua::new();
-    assert!(lua
-        .globals()
-        .get::<_, String>("_VERSION")?
-        .starts_with("Luau 0."));
+    assert!(lua.globals().get::<_, String>("_VERSION")?.starts_with("Luau 0."));
     Ok(())
 }
 
@@ -189,9 +186,7 @@ fn test_vector_metatable() -> Result<()> {
     lua.set_vector_metatable(Some(vector_mt.clone()));
     lua.globals().set("Vector3", vector_mt)?;
 
-    let compiler = Compiler::new()
-        .set_vector_lib("Vector3")
-        .set_vector_ctor("new");
+    let compiler = Compiler::new().set_vector_lib("Vector3").set_vector_ctor("new");
 
     // Test vector methods (fastcall)
     lua.load(

tests/memory.rs

@@ -68,12 +68,7 @@ fn test_gc_control() -> Result<()> {
         assert_eq!(lua.gc_inc(0, 0, 0), GCMode::Generational);
     }
 
-    #[cfg(any(
-        feature = "lua54",
-        feature = "lua53",
-        feature = "lua52",
-        feature = "luau"
-    ))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52", feature = "luau"))]
     {
         assert!(lua.gc_is_running());
         lua.gc_stop();

tests/serde.rs

@@ -4,8 +4,8 @@ use std::collections::HashMap;
 use std::error::Error as StdError;
 
 use mlua::{
-    DeserializeOptions, Error, ExternalResult, Lua, LuaSerdeExt, Result as LuaResult,
-    SerializeOptions, UserData, Value,
+    DeserializeOptions, Error, ExternalResult, Lua, LuaSerdeExt, Result as LuaResult, SerializeOptions,
+    UserData, Value,
 };
 use serde::{Deserialize, Serialize};
 
@@ -71,49 +71,49 @@ fn test_serialize() -> Result<(), Box<dyn StdError>> {
     Ok(())
 }
 
-#[test]
-fn test_serialize_in_scope() -> LuaResult<()> {
-    #[derive(Serialize, Clone)]
-    struct MyUserData(i64, String);
+// #[test]
+// fn test_serialize_in_scope() -> LuaResult<()> {
+//     #[derive(Serialize, Clone)]
+//     struct MyUserData(i64, String);
 
-    impl UserData for MyUserData {}
+//     impl UserData for MyUserData {}
 
-    let lua = Lua::new();
-    lua.scope(|scope| {
-        let ud = scope.create_ser_userdata(MyUserData(-5, "test userdata".into()))?;
-        assert_eq!(
-            serde_json::to_value(&ud).unwrap(),
-            serde_json::json!((-5, "test userdata"))
-        );
-        Ok(())
-    })?;
+//     let lua = Lua::new();
+//     lua.scope(|scope| {
+//         let ud = scope.create_ser_userdata(MyUserData(-5, "test userdata".into()))?;
+//         assert_eq!(
+//             serde_json::to_value(&ud).unwrap(),
+//             serde_json::json!((-5, "test userdata"))
+//         );
+//         Ok(())
+//     })?;
 
-    lua.scope(|scope| {
-        let ud = scope.create_ser_userdata(MyUserData(-5, "test userdata".into()))?;
-        lua.globals().set("ud", ud)
-    })?;
-    let val = lua.load("ud").eval::<Value>()?;
-    match serde_json::to_value(&val) {
-        Ok(v) => panic!("expected destructed error, got {}", v),
-        Err(e) if e.to_string().contains("destructed") => {}
-        Err(e) => panic!("expected destructed error, got {}", e),
-    }
+//     lua.scope(|scope| {
+//         let ud = scope.create_ser_userdata(MyUserData(-5, "test userdata".into()))?;
+//         lua.globals().set("ud", ud)
+//     })?;
+//     let val = lua.load("ud").eval::<Value>()?;
+//     match serde_json::to_value(&val) {
+//         Ok(v) => panic!("expected destructed error, got {}", v),
+//         Err(e) if e.to_string().contains("destructed") => {}
+//         Err(e) => panic!("expected destructed error, got {}", e),
+//     }
 
-    struct MyUserDataRef<'a>(#[allow(unused)] &'a ());
+//     struct MyUserDataRef<'a>(#[allow(unused)] &'a ());
 
-    impl<'a> UserData for MyUserDataRef<'a> {}
+//     impl<'a> UserData for MyUserDataRef<'a> {}
 
-    lua.scope(|scope| {
-        let ud = scope.create_nonstatic_userdata(MyUserDataRef(&()))?;
-        match serde_json::to_value(&ud) {
-            Ok(v) => panic!("expected serialization error, got {}", v),
-            Err(serde_json::Error { .. }) => {}
-        };
-        Ok(())
-    })?;
+//     lua.scope(|scope| {
+//         let ud = scope.create_nonstatic_userdata(MyUserDataRef(&()))?;
+//         match serde_json::to_value(&ud) {
+//             Ok(v) => panic!("expected serialization error, got {}", v),
+//             Err(serde_json::Error { .. }) => {}
+//         };
+//         Ok(())
+//     })?;
 
-    Ok(())
-}
+//     Ok(())
+// }
 
 #[test]
 fn test_serialize_any_userdata() -> Result<(), Box<dyn StdError>> {
@@ -395,10 +395,7 @@ fn test_to_value_with_options() -> Result<(), Box<dyn StdError>> {
         unit: (),
         unitstruct: UnitStruct,
     };
-    let data2 = lua.to_value_with(
-        &mydata,
-        SerializeOptions::new().serialize_none_to_null(false),
-    )?;
+    let data2 = lua.to_value_with(&mydata, SerializeOptions::new().serialize_none_to_null(false))?;
     globals.set("data2", data2)?;
     lua.load(
         r#"
@@ -410,10 +407,7 @@ fn test_to_value_with_options() -> Result<(), Box<dyn StdError>> {
     .exec()?;
 
     // serialize_unit_to_null
-    let data3 = lua.to_value_with(
-        &mydata,
-        SerializeOptions::new().serialize_unit_to_null(false),
-    )?;
+    let data3 = lua.to_value_with(&mydata, SerializeOptions::new().serialize_unit_to_null(false))?;
     globals.set("data3", data3)?;
     lua.load(
         r#"

tests/static.rs

@@ -7,7 +7,7 @@ fn test_static_lua() -> Result<()> {
     let lua = Lua::new().into_static();
 
     thread_local! {
-        static TABLE: RefCell<Option<Table<'static>>> = RefCell::new(None);
+        static TABLE: RefCell<Option<Table>> = RefCell::new(None);
     }
 
     let f = lua.create_function(|_, table: Table| {
@@ -38,7 +38,7 @@ fn test_static_lua_coroutine() -> Result<()> {
     let lua = Lua::new().into_static();
 
     thread_local! {
-        static TABLE: RefCell<Option<Table<'static>>> = RefCell::new(None);
+        static TABLE: RefCell<Option<Table>> = RefCell::new(None);
     }
 
     let f = lua.create_function(|_, table: Table| {
@@ -83,16 +83,15 @@ async fn test_static_async() -> Result<()> {
         tokio::task::yield_now().await;
     }
 
-    let timer =
-        lua.create_async_function(|_, (i, n, f): (u64, u64, mlua::Function)| async move {
-            tokio::task::spawn_local(async move {
-                for _ in 0..n {
-                    tokio::task::spawn_local(f.call_async::<(), ()>(()));
-                    sleep_ms(i).await;
-                }
-            });
-            Ok(())
-        })?;
+    let timer = lua.create_async_function(|_, (i, n, f): (u64, u64, mlua::Function)| async move {
+        tokio::task::spawn_local(async move {
+            for _ in 0..n {
+                tokio::task::spawn_local(f.call_async::<(), ()>(()));
+                sleep_ms(i).await;
+            }
+        });
+        Ok(())
+    })?;
     lua.globals().set("timer", timer)?;
 
     {

tests/string.rs

@@ -15,9 +15,7 @@ fn test_string_compare() {
     with_str("teststring", |t| assert_eq!(t, b"teststring".to_vec())); // Vec<u8>
     with_str("teststring", |t| assert_eq!(t, "teststring".to_string())); // String
     with_str("teststring", |t| assert_eq!(t, t)); // mlua::String
-    with_str("teststring", |t| {
-        assert_eq!(t, Cow::from(b"teststring".as_ref()))
-    }); // Cow (borrowed)
+    with_str("teststring", |t| assert_eq!(t, Cow::from(b"teststring".as_ref()))); // Cow (borrowed)
     with_str("bla", |t| assert_eq!(t, Cow::from(b"bla".to_vec()))); // Cow (owned)
 }
 
@@ -40,14 +38,8 @@ fn test_string_views() -> Result<()> {
     let empty: String = globals.get("empty")?;
 
     assert_eq!(ok.to_str()?, "null bytes are valid utf-8, wh\0 knew?");
-    assert_eq!(
-        ok.to_string_lossy(),
-        "null bytes are valid utf-8, wh\0 knew?"
-    );
-    assert_eq!(
-        ok.as_bytes(),
-        &b"null bytes are valid utf-8, wh\0 knew?"[..]
-    );
+    assert_eq!(ok.to_string_lossy(), "null bytes are valid utf-8, wh\0 knew?");
+    assert_eq!(ok.as_bytes(), &b"null bytes are valid utf-8, wh\0 knew?"[..]);
 
     assert!(err.to_str().is_err());
     assert_eq!(err.as_bytes(), &b"but \xff isn't :("[..]);
@@ -75,11 +67,11 @@ fn test_string_hash() -> Result<()> {
 
     let set: HashSet<String> = lua.load(r#"{"hello", "world", "abc", 321}"#).eval()?;
     assert_eq!(set.len(), 4);
-    assert!(set.contains(b"hello".as_ref()));
-    assert!(set.contains(b"world".as_ref()));
-    assert!(set.contains(b"abc".as_ref()));
-    assert!(set.contains(b"321".as_ref()));
-    assert!(!set.contains(b"Hello".as_ref()));
+    assert!(set.contains(&lua.create_string("hello")?));
+    assert!(set.contains(&lua.create_string("world")?));
+    assert!(set.contains(&lua.create_string("abc")?));
+    assert!(set.contains(&lua.create_string("321")?));
+    assert!(!set.contains(&lua.create_string("Hello")?));
 
     Ok(())
 }
@@ -111,22 +103,3 @@ fn test_string_pointer() -> Result<()> {
 
     Ok(())
 }
-
-#[cfg(all(feature = "unstable", not(feature = "send")))]
-#[test]
-fn test_owned_string() -> Result<()> {
-    let lua = Lua::new();
-
-    let s = lua.create_string("hello, world!")?.into_owned();
-    drop(lua);
-
-    // Shortcuts
-    assert_eq!(s.as_bytes(), b"hello, world!");
-    assert_eq!(s.to_str()?, "hello, world!");
-    assert_eq!(format!("{s:?}"), "\"hello, world!\"");
-
-    // Access via reference
-    assert_eq!(s.to_ref().to_string_lossy(), "hello, world!");
-
-    Ok(())
-}

tests/table.rs

@@ -45,17 +45,11 @@ fn test_table() -> Result<()> {
     assert_eq!(table1.len()?, 5);
     assert!(!table1.is_empty());
     assert_eq!(
-        table1
-            .clone()
-            .pairs()
-            .collect::<Result<Vec<(i64, i64)>>>()?,
+        table1.clone().pairs().collect::<Result<Vec<(i64, i64)>>>()?,
         vec![(1, 1), (2, 2), (3, 3), (4, 4), (5, 5)]
     );
     assert_eq!(
-        table1
-            .clone()
-            .sequence_values()
-            .collect::<Result<Vec<i64>>>()?,
+        table1.clone().sequence_values().collect::<Result<Vec<i64>>>()?,
         vec![1, 2, 3, 4, 5]
     );
     assert_eq!(table1, [1, 2, 3, 4, 5]);
@@ -63,10 +57,7 @@ fn test_table() -> Result<()> {
     assert_eq!(table2.len()?, 0);
     assert!(table2.is_empty());
     assert_eq!(
-        table2
-            .clone()
-            .pairs()
-            .collect::<Result<Vec<(i64, i64)>>>()?,
+        table2.clone().pairs().collect::<Result<Vec<(i64, i64)>>>()?,
         vec![]
     );
     assert_eq!(table2, [0; 0]);
@@ -81,29 +72,20 @@ fn test_table() -> Result<()> {
     globals.set("table4", lua.create_sequence_from(vec![1, 2, 3, 4, 5])?)?;
     let table4 = globals.get::<_, Table>("table4")?;
     assert_eq!(
-        table4
-            .clone()
-            .pairs()
-            .collect::<Result<Vec<(i64, i64)>>>()?,
+        table4.clone().pairs().collect::<Result<Vec<(i64, i64)>>>()?,
         vec![(1, 1), (2, 2), (3, 3), (4, 4), (5, 5)]
     );
 
     table4.raw_insert(4, 35)?;
     table4.raw_insert(7, 7)?;
     assert_eq!(
-        table4
-            .clone()
-            .pairs()
-            .collect::<Result<Vec<(i64, i64)>>>()?,
+        table4.clone().pairs().collect::<Result<Vec<(i64, i64)>>>()?,
         vec![(1, 1), (2, 2), (3, 3), (4, 35), (5, 4), (6, 5), (7, 7)]
     );
 
     table4.raw_remove(1)?;
     assert_eq!(
-        table4
-            .clone()
-            .pairs()
-            .collect::<Result<Vec<(i64, i64)>>>()?,
+        table4.clone().pairs().collect::<Result<Vec<(i64, i64)>>>()?,
         vec![(1, 2), (2, 3), (3, 35), (4, 4), (5, 5), (6, 7)]
     );
 
@@ -448,24 +430,7 @@ fn test_table_call() -> Result<()> {
 
     // Test calling non-callable table
     let table2 = lua.create_table()?;
-    assert!(matches!(
-        table2.call::<_, ()>(()),
-        Err(Error::RuntimeError(_))
-    ));
-
-    Ok(())
-}
-
-#[cfg(all(feature = "unstable", not(feature = "send")))]
-#[test]
-fn test_owned_table() -> Result<()> {
-    let lua = Lua::new();
-
-    let table = lua.create_table()?.into_owned();
-    drop(lua);
-
-    table.to_ref().set("abc", 123)?;
-    assert_eq!(table.to_ref().get::<_, i64>("abc")?, 123);
+    assert!(matches!(table2.call::<_, ()>(()), Err(Error::RuntimeError(_))));
 
     Ok(())
 }

tests/tests.rs

@@ -8,8 +8,8 @@ use std::sync::Arc;
 use std::{error, f32, f64, fmt};
 
 use mlua::{
-    ChunkMode, Error, ExternalError, Function, Lua, LuaOptions, Nil, Result, StdLib, String, Table,
-    UserData, Value, Variadic,
+    ChunkMode, Error, ExternalError, Function, Lua, LuaOptions, Nil, Result, StdLib, String, Table, UserData,
+    Value, Variadic,
 };
 
 #[cfg(not(feature = "luau"))]
@@ -17,7 +17,7 @@ use mlua::{
 fn test_safety() -> Result<()> {
     let lua = Lua::new();
     assert!(lua.load(r#"require "debug""#).exec().is_err());
-    match lua.load_from_std_lib(StdLib::DEBUG) {
+    match lua.load_std_libs(StdLib::DEBUG) {
         Err(Error::SafetyError(_)) => {}
         Err(e) => panic!("expected SafetyError, got {:?}", e),
         Ok(_) => panic!("expected SafetyError, got no error"),
@@ -53,7 +53,7 @@ fn test_safety() -> Result<()> {
     // Test safety rules after dynamically loading `package` library
     let lua = Lua::new_with(StdLib::NONE, LuaOptions::default())?;
     assert!(lua.globals().get::<_, Option<Value>>("require")?.is_none());
-    lua.load_from_std_lib(StdLib::PACKAGE)?;
+    lua.load_std_libs(StdLib::PACKAGE)?;
     match lua.load(r#"package.loadlib()"#).exec() {
         Err(Error::CallbackError { ref cause, .. }) => match cause.as_ref() {
             Error::SafetyError(_) => {}
@@ -108,10 +108,7 @@ fn test_exec() -> Result<()> {
         .eval()?;
     println!("checkpoint");
     assert!(module.contains_key("func")?);
-    assert_eq!(
-        module.get::<_, Function>("func")?.call::<_, String>(())?,
-        "hello"
-    );
+    assert_eq!(module.get::<_, Function>("func")?.call::<_, String>(())?, "hello");
 
     Ok(())
 }
@@ -128,10 +125,7 @@ fn test_eval() -> Result<()> {
             incomplete_input: true,
             ..
         }) => {}
-        r => panic!(
-            "expected SyntaxError with incomplete_input=true, got {:?}",
-            r
-        ),
+        r => panic!("expected SyntaxError with incomplete_input=true, got {:?}", r),
     }
 
     Ok(())
@@ -141,10 +135,7 @@ fn test_eval() -> Result<()> {
 fn test_load_mode() -> Result<()> {
     let lua = unsafe { Lua::unsafe_new() };
 
-    assert_eq!(
-        lua.load("1 + 1").set_mode(ChunkMode::Text).eval::<i32>()?,
-        2
-    );
+    assert_eq!(lua.load("1 + 1").set_mode(ChunkMode::Text).eval::<i32>()?, 2);
     match lua.load("1 + 1").set_mode(ChunkMode::Binary).exec() {
         Ok(_) => panic!("expected SyntaxError, got no error"),
         Err(Error::SyntaxError { message: msg, .. }) => {
@@ -158,12 +149,7 @@ fn test_load_mode() -> Result<()> {
     #[cfg(feature = "luau")]
     let bytecode = mlua::Compiler::new().compile("return 1 + 1");
     assert_eq!(lua.load(&bytecode).eval::<i32>()?, 2);
-    assert_eq!(
-        lua.load(&bytecode)
-            .set_mode(ChunkMode::Binary)
-            .eval::<i32>()?,
-        2
-    );
+    assert_eq!(lua.load(&bytecode).set_mode(ChunkMode::Binary).eval::<i32>()?, 2);
     match lua.load(&bytecode).set_mode(ChunkMode::Text).exec() {
         Ok(_) => panic!("expected SyntaxError, got no error"),
         Err(Error::SyntaxError { message: msg, .. }) => {
@@ -308,8 +294,7 @@ fn test_error() -> Result<()> {
     )
     .exec()?;
 
-    let rust_error_function =
-        lua.create_function(|_, ()| -> Result<()> { Err(TestError.into_lua_err()) })?;
+    let rust_error_function = lua.create_function(|_, ()| -> Result<()> { Err(TestError.into_lua_err()) })?;
     globals.set("rust_error_function", rust_error_function)?;
 
     let no_error = globals.get::<_, Function>("no_error")?;
@@ -338,10 +323,7 @@ fn test_error() -> Result<()> {
     let return_string_error = globals.get::<_, Function>("return_string_error")?;
     assert!(return_string_error.call::<_, Error>(()).is_ok());
 
-    match lua
-        .load("if youre happy and you know it syntax error")
-        .exec()
-    {
+    match lua.load("if youre happy and you know it syntax error").exec() {
         Err(Error::SyntaxError {
             incomplete_input: false,
             ..
@@ -374,15 +356,13 @@ fn test_error() -> Result<()> {
 fn test_panic() -> Result<()> {
     fn make_lua(options: LuaOptions) -> Result<Lua> {
         let lua = Lua::new_with(StdLib::ALL_SAFE, options)?;
-        let rust_panic_function =
-            lua.create_function(|_, msg: Option<StdString>| -> Result<()> {
-                if let Some(msg) = msg {
-                    panic!("{}", msg)
-                }
-                panic!("rust panic")
-            })?;
-        lua.globals()
-            .set("rust_panic_function", rust_panic_function)?;
+        let rust_panic_function = lua.create_function(|_, msg: Option<StdString>| -> Result<()> {
+            if let Some(msg) = msg {
+                panic!("{}", msg)
+            }
+            panic!("rust panic")
+        })?;
+        lua.globals().set("rust_panic_function", rust_panic_function)?;
         Ok(lua)
     }
 
@@ -538,12 +518,7 @@ fn test_num_conversion() -> Result<()> {
     assert_eq!(lua.load("1.0").eval::<f64>()?, 1.0);
     #[cfg(any(feature = "lua54", feature = "lua53"))]
     assert_eq!(lua.load("1.0").eval::<String>()?, "1.0");
-    #[cfg(any(
-        feature = "lua52",
-        feature = "lua51",
-        feature = "luajit",
-        feature = "luau"
-    ))]
+    #[cfg(any(feature = "lua52", feature = "lua51", feature = "luajit", feature = "luau"))]
     assert_eq!(lua.load("1.0").eval::<String>()?, "1");
 
     assert_eq!(lua.load("1.5").eval::<i64>()?, 1);
@@ -620,12 +595,7 @@ fn test_pcall_xpcall() -> Result<()> {
     assert_eq!(globals.get::<_, String>("pcall_error")?, "testerror");
 
     assert_eq!(globals.get::<_, bool>("xpcall_statusr")?, false);
-    #[cfg(any(
-        feature = "lua54",
-        feature = "lua53",
-        feature = "lua52",
-        feature = "luajit"
-    ))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52", feature = "luajit"))]
     assert_eq!(
         globals.get::<_, std::string::String>("xpcall_error")?,
         "testerror"
@@ -645,9 +615,7 @@ fn test_pcall_xpcall() -> Result<()> {
     "#,
     )
     .exec()?;
-    let _ = globals
-        .get::<_, Function>("xpcall_recursion")?
-        .call::<_, ()>(());
+    let _ = globals.get::<_, Function>("xpcall_recursion")?.call::<_, ()>(());
 
     Ok(())
 }
@@ -657,7 +625,7 @@ fn test_recursive_mut_callback_error() -> Result<()> {
     let lua = Lua::new();
 
     let mut v = Some(Box::new(123));
-    let f = lua.create_function_mut::<_, (), _>(move |lua, mutate: bool| {
+    let f = lua.create_function_mut(move |lua, mutate: bool| {
         if mutate {
             v = None;
         } else {
@@ -767,18 +735,18 @@ fn test_drop_registry_value() -> Result<()> {
 fn test_replace_registry_value() -> Result<()> {
     let lua = Lua::new();
 
-    let key = lua.create_registry_value::<i32>(42)?;
-    lua.replace_registry_value(&key, "new value")?;
+    let mut key = lua.create_registry_value::<i32>(42)?;
+    lua.replace_registry_value(&mut key, "new value")?;
     assert_eq!(lua.registry_value::<String>(&key)?, "new value");
-    lua.replace_registry_value(&key, Value::Nil)?;
+    lua.replace_registry_value(&mut key, Value::Nil)?;
     assert_eq!(lua.registry_value::<Value>(&key)?, Value::Nil);
-    lua.replace_registry_value(&key, 123)?;
+    lua.replace_registry_value(&mut key, 123)?;
     assert_eq!(lua.registry_value::<i32>(&key)?, 123);
 
-    let key2 = lua.create_registry_value(Value::Nil)?;
-    lua.replace_registry_value(&key2, Value::Nil)?;
+    let mut key2 = lua.create_registry_value(Value::Nil)?;
+    lua.replace_registry_value(&mut key2, Value::Nil)?;
     assert_eq!(lua.registry_value::<Value>(&key2)?, Value::Nil);
-    lua.replace_registry_value(&key2, "abc")?;
+    lua.replace_registry_value(&mut key2, "abc")?;
     assert_eq!(lua.registry_value::<String>(&key2)?, "abc");
 
     Ok(())
@@ -901,10 +869,7 @@ fn test_application_data() -> Result<()> {
     f.call(())?;
 
     assert_eq!(*lua.app_data_ref::<&str>().unwrap(), "test4");
-    assert_eq!(
-        *lua.app_data_ref::<Vec<&str>>().unwrap(),
-        vec!["test2", "test3"]
-    );
+    assert_eq!(*lua.app_data_ref::<Vec<&str>>().unwrap(), vec!["test2", "test3"]);
 
     lua.remove_app_data::<Vec<&str>>();
     assert!(matches!(lua.app_data_ref::<Vec<&str>>(), None));
@@ -919,9 +884,7 @@ fn test_recursion() -> Result<()> {
 
     let f = lua.create_function(move |lua, i: i32| {
         if i < 64 {
-            lua.globals()
-                .get::<_, Function>("f")?
-                .call::<_, ()>(i + 1)?;
+            lua.globals().get::<_, Function>("f")?.call::<_, ()>(i + 1)?;
         }
         Ok(())
     })?;
@@ -961,8 +924,7 @@ fn test_too_many_arguments() -> Result<()> {
 fn test_too_many_recursions() -> Result<()> {
     let lua = Lua::new();
 
-    let f = lua
-        .create_function(move |lua, ()| lua.globals().get::<_, Function>("f")?.call::<_, ()>(()))?;
+    let f = lua.create_function(move |lua, ()| lua.globals().get::<_, Function>("f")?.call::<_, ()>(()))?;
 
     lua.globals().set("f", &f)?;
     assert!(f.call::<_, ()>(()).is_err());
@@ -985,9 +947,7 @@ fn test_too_many_binds() -> Result<()> {
 
     let concat = globals.get::<_, Function>("f")?;
     assert!(concat.bind(Variadic::from_iter(1..1000000)).is_err());
-    assert!(concat
-        .call::<_, ()>(Variadic::from_iter(1..1000000))
-        .is_err());
+    assert!(concat.call::<_, ()>(Variadic::from_iter(1..1000000)).is_err());
 
     Ok(())
 }
@@ -1038,10 +998,7 @@ fn test_large_args() -> Result<()> {
         )
         .eval()?;
 
-    assert_eq!(
-        f.call::<_, usize>((0..100).collect::<Variadic<usize>>())?,
-        4950
-    );
+    assert_eq!(f.call::<_, usize>((0..100).collect::<Variadic<usize>>())?, 4950);
 
     Ok(())
 }
@@ -1110,12 +1067,7 @@ fn test_context_thread() -> Result<()> {
         )
         .into_function()?;
 
-    #[cfg(any(
-        feature = "lua54",
-        feature = "lua53",
-        feature = "lua52",
-        feature = "luajit52"
-    ))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52", feature = "luajit52"))]
     f.call::<_, ()>(lua.current_thread())?;
 
     #[cfg(any(
@@ -1154,10 +1106,7 @@ fn test_context_thread_51() -> Result<()> {
 fn test_jit_version() -> Result<()> {
     let lua = Lua::new();
     let jit: Table = lua.globals().get("jit")?;
-    assert!(jit
-        .get::<_, String>("version")?
-        .to_str()?
-        .contains("LuaJIT"));
+    assert!(jit.get::<_, String>("version")?.to_str()?.contains("LuaJIT"));
     Ok(())
 }
 
@@ -1324,11 +1273,26 @@ fn test_luajit_cdata() -> Result<()> {
 #[test]
 #[cfg(feature = "send")]
 #[cfg(not(target_arch = "wasm32"))]
-fn test_send() {
+fn test_multi_thread() -> Result<()> {
     let lua = Lua::new();
-    std::thread::spawn(move || {
-        let _lua = lua;
-    })
-    .join()
-    .unwrap();
+
+    lua.globals().set("i", 0)?;
+    let func = lua.load("i = i + 1").into_function()?;
+
+    std::thread::scope(|s| {
+        s.spawn(|| {
+            for _ in 0..5 {
+                func.call::<_, ()>(()).unwrap();
+            }
+        });
+        s.spawn(|| {
+            for _ in 0..5 {
+                func.call::<_, ()>(()).unwrap();
+            }
+        });
+    });
+
+    assert_eq!(lua.globals().get::<_, i32>("i")?, 10);
+
+    Ok(())
 }

tests/thread.rs

@@ -231,34 +231,3 @@ fn test_thread_pointer() -> Result<()> {
 
     Ok(())
 }
-
-#[cfg(all(feature = "unstable", not(feature = "send")))]
-#[test]
-fn test_owned_thread() -> Result<()> {
-    let lua = Lua::new();
-
-    let accumulate = lua
-        .create_thread(
-            lua.load(
-                r#"
-            function (sum)
-                while true do
-                    sum = sum + coroutine.yield(sum)
-                end
-            end
-            "#,
-            )
-            .eval::<Function>()?,
-        )?
-        .into_owned();
-
-    for i in 0..4 {
-        accumulate.resume::<_, ()>(i)?;
-    }
-    assert_eq!(accumulate.resume::<_, i64>(4)?, 10);
-    assert_eq!(accumulate.status(), ThreadStatus::Resumable);
-    assert!(accumulate.resume::<_, ()>("error").is_err());
-    assert_eq!(accumulate.status(), ThreadStatus::Error);
-
-    Ok(())
-}

tests/userdata.rs

@@ -1,21 +1,13 @@
 use std::collections::HashMap;
 use std::string::String as StdString;
 use std::sync::Arc;
-#[cfg(not(feature = "parking_lot"))]
-use std::sync::{Mutex, RwLock};
-
-#[cfg(feature = "parking_lot")]
-use parking_lot::{Mutex, RwLock};
-
-#[cfg(not(feature = "send"))]
-use std::{cell::RefCell, rc::Rc};
 
 #[cfg(feature = "lua54")]
 use std::sync::atomic::{AtomicI64, Ordering};
 
 use mlua::{
-    AnyUserData, AnyUserDataExt, Error, ExternalError, Function, Lua, MetaMethod, Nil, Result,
-    String, UserData, UserDataFields, UserDataMethods, UserDataRef, Value, Variadic,
+    AnyUserData, AnyUserDataExt, Error, ExternalError, Function, Lua, MetaMethod, Nil, Result, String,
+    UserData, UserDataFields, UserDataMethods, UserDataRef, Value, Variadic,
 };
 
 #[test]
@@ -47,7 +39,7 @@ fn test_methods() -> Result<()> {
     struct MyUserData(i64);
 
     impl UserData for MyUserData {
-        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+        fn add_methods<'a, M: UserDataMethods<'a, Self>>(methods: &mut M) {
             methods.add_method("get_value", |_, data, ()| Ok(data.0));
             methods.add_method_mut("set_value", |_, data, args| {
                 data.0 = args;
@@ -97,7 +89,7 @@ fn test_method_variadic() -> Result<()> {
     struct MyUserData(i64);
 
     impl UserData for MyUserData {
-        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+        fn add_methods<'a, M: UserDataMethods<'a, Self>>(methods: &mut M) {
             methods.add_method("get", |_, data, ()| Ok(data.0));
             methods.add_method_mut("add", |_, data, vals: Variadic<i64>| {
                 data.0 += vals.into_iter().sum::<i64>();
@@ -122,19 +114,15 @@ fn test_metamethods() -> Result<()> {
     struct MyUserData(i64);
 
     impl UserData for MyUserData {
-        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+        fn add_methods<'a, M: UserDataMethods<'a, Self>>(methods: &mut M) {
             methods.add_method("get", |_, data, ()| Ok(data.0));
             methods.add_meta_function(
                 MetaMethod::Add,
-                |_, (lhs, rhs): (UserDataRef<Self>, UserDataRef<Self>)| {
-                    Ok(MyUserData(lhs.0 + rhs.0))
-                },
+                |_, (lhs, rhs): (UserDataRef<Self>, UserDataRef<Self>)| Ok(MyUserData(lhs.0 + rhs.0)),
             );
             methods.add_meta_function(
                 MetaMethod::Sub,
-                |_, (lhs, rhs): (UserDataRef<Self>, UserDataRef<Self>)| {
-                    Ok(MyUserData(lhs.0 - rhs.0))
-                },
+                |_, (lhs, rhs): (UserDataRef<Self>, UserDataRef<Self>)| Ok(MyUserData(lhs.0 - rhs.0)),
             );
             methods.add_meta_function(
                 MetaMethod::Eq,
@@ -147,22 +135,16 @@ fn test_metamethods() -> Result<()> {
                     Err("no such custom index".into_lua_err())
                 }
             });
-            #[cfg(any(
-                feature = "lua54",
-                feature = "lua53",
-                feature = "lua52",
-                feature = "luajit52"
-            ))]
+            #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52", feature = "luajit52"))]
             methods.add_meta_method(MetaMethod::Pairs, |lua, data, ()| {
                 use std::iter::FromIterator;
-                let stateless_iter =
-                    lua.create_function(|_, (data, i): (UserDataRef<Self>, i64)| {
-                        let i = i + 1;
-                        if i <= data.0 {
-                            return Ok(mlua::Variadic::from_iter(vec![i, i]));
-                        }
-                        return Ok(mlua::Variadic::new());
-                    })?;
+                let stateless_iter = lua.create_function(|_, (data, i): (UserDataRef<Self>, i64)| {
+                    let i = i + 1;
+                    if i <= data.0 {
+                        return Ok(mlua::Variadic::from_iter(vec![i, i]));
+                    }
+                    return Ok(mlua::Variadic::new());
+                })?;
                 Ok((stateless_iter, data.clone(), 0))
             });
         }
@@ -180,12 +162,7 @@ fn test_metamethods() -> Result<()> {
         10
     );
 
-    #[cfg(any(
-        feature = "lua54",
-        feature = "lua53",
-        feature = "lua52",
-        feature = "luajit52"
-    ))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52", feature = "luajit52"))]
     let pairs_it = lua
         .load(
             r#"
@@ -210,12 +187,7 @@ fn test_metamethods() -> Result<()> {
     assert_eq!(lua.load("userdata2.inner").eval::<i64>()?, 3);
     assert!(lua.load("userdata2.nonexist_field").eval::<()>().is_err());
 
-    #[cfg(any(
-        feature = "lua54",
-        feature = "lua53",
-        feature = "lua52",
-        feature = "luajit52"
-    ))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52", feature = "luajit52"))]
     assert_eq!(pairs_it.call::<_, i64>(())?, 28);
 
     let userdata2: Value = globals.get("userdata2")?;
@@ -241,7 +213,7 @@ fn test_metamethod_close() -> Result<()> {
     struct MyUserData(Arc<AtomicI64>);
 
     impl UserData for MyUserData {
-        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+        fn add_methods<'a, M: UserDataMethods<'a, Self>>(methods: &mut M) {
             methods.add_method("get", |_, data, ()| Ok(data.0.load(Ordering::Relaxed)));
             methods.add_meta_method(MetaMethod::Close, |_, data, _err: Value| {
                 data.0.store(0, Ordering::Relaxed);
@@ -287,7 +259,7 @@ fn test_gc_userdata() -> Result<()> {
     }
 
     impl UserData for MyUserdata {
-        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+        fn add_methods<'a, M: UserDataMethods<'a, Self>>(methods: &mut M) {
             methods.add_method("access", |_, this, ()| {
                 assert!(this.id == 123);
                 Ok(())
@@ -326,7 +298,7 @@ fn test_userdata_take() -> Result<()> {
     struct MyUserdata(Arc<i64>);
 
     impl UserData for MyUserdata {
-        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+        fn add_methods<'a, M: UserDataMethods<'a, Self>>(methods: &mut M) {
             methods.add_method("num", |_, this, ()| Ok(*this.0))
         }
     }
@@ -461,10 +433,8 @@ fn test_functions() -> Result<()> {
     struct MyUserData(i64);
 
     impl UserData for MyUserData {
-        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
-            methods.add_function("get_value", |_, ud: AnyUserData| {
-                Ok(ud.borrow::<MyUserData>()?.0)
-            });
+        fn add_methods<'a, M: UserDataMethods<'a, Self>>(methods: &mut M) {
+            methods.add_function("get_value", |_, ud: AnyUserData| Ok(ud.borrow::<MyUserData>()?.0));
             methods.add_function_mut("set_value", |_, (ud, value): (AnyUserData, i64)| {
                 ud.borrow_mut::<MyUserData>()?.0 = value;
                 Ok(())
@@ -515,7 +485,7 @@ fn test_fields() -> Result<()> {
     struct MyUserData(i64);
 
     impl UserData for MyUserData {
-        fn add_fields<'lua, F: UserDataFields<'lua, Self>>(fields: &mut F) {
+        fn add_fields<'a, F: UserDataFields<'a, Self>>(fields: &mut F) {
             fields.add_field("static", "constant");
             fields.add_field_method_get("val", |_, data| Ok(data.0));
             fields.add_field_method_set("val", |_, data, val| {
@@ -525,8 +495,7 @@ fn test_fields() -> Result<()> {
 
             // Use userdata "uservalue" storage
             fields.add_field_function_get("uval", |_, ud| ud.user_value::<Option<String>>());
-            fields
-                .add_field_function_set("uval", |_, ud, s| ud.set_user_value::<Option<String>>(s));
+            fields.add_field_function_set("uval", |_, ud, s| ud.set_user_value::<Option<String>>(s));
 
             fields.add_meta_field(MetaMethod::Index, HashMap::from([("f", 321)]));
             fields.add_meta_field_with(MetaMethod::NewIndex, |lua| {
@@ -562,12 +531,12 @@ fn test_fields() -> Result<()> {
     struct MyUserData2(i64);
 
     impl UserData for MyUserData2 {
-        fn add_fields<'lua, F: UserDataFields<'lua, Self>>(fields: &mut F) {
+        fn add_fields<'a, F: UserDataFields<'a, Self>>(fields: &mut F) {
             fields.add_field("z", 0);
             fields.add_field_method_get("x", |_, data| Ok(data.0));
         }
 
-        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+        fn add_methods<'a, M: UserDataMethods<'a, Self>>(methods: &mut M) {
             methods.add_meta_method(MetaMethod::Index, |_, _, name: StdString| match &*name {
                 "y" => Ok(Some(-1)),
                 _ => Ok(None),
@@ -594,7 +563,7 @@ fn test_metatable() -> Result<()> {
     struct MyUserData;
 
     impl UserData for MyUserData {
-        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+        fn add_methods<'a, M: UserDataMethods<'a, Self>>(methods: &mut M) {
             methods.add_function("my_type_name", |_, data: AnyUserData| {
                 let metatable = data.get_metatable()?;
                 metatable.get::<String>(MetaMethod::Type)
@@ -605,8 +574,7 @@ fn test_metatable() -> Result<()> {
     let lua = Lua::new();
     let globals = lua.globals();
     globals.set("ud", MyUserData)?;
-    lua.load(r#"assert(ud:my_type_name() == "MyUserData")"#)
-        .exec()?;
+    lua.load(r#"assert(ud:my_type_name() == "MyUserData")"#).exec()?;
 
     #[cfg(any(feature = "lua54", feature = "lua53", feature = "luau"))]
     lua.load(r#"assert(tostring(ud):sub(1, 11) == "MyUserData:")"#)
@@ -640,7 +608,7 @@ fn test_metatable() -> Result<()> {
     struct MyUserData2;
 
     impl UserData for MyUserData2 {
-        fn add_fields<'lua, F: UserDataFields<'lua, Self>>(fields: &mut F) {
+        fn add_fields<'a, F: UserDataFields<'a, Self>>(fields: &mut F) {
             fields.add_meta_field_with("__index", |_| Ok(1));
         }
     }
@@ -655,136 +623,14 @@ fn test_metatable() -> Result<()> {
     struct MyUserData3;
 
     impl UserData for MyUserData3 {
-        fn add_fields<'lua, F: UserDataFields<'lua, Self>>(fields: &mut F) {
+        fn add_fields<'a, F: UserDataFields<'a, Self>>(fields: &mut F) {
             fields.add_meta_field_with(MetaMethod::Type, |_| Ok("CustomName"));
         }
     }
 
     let ud = lua.create_userdata(MyUserData3)?;
     let metatable = ud.get_metatable()?;
-    assert_eq!(
-        metatable.get::<String>(MetaMethod::Type)?.to_str()?,
-        "CustomName"
-    );
-
-    Ok(())
-}
-
-#[test]
-fn test_userdata_wrapped() -> Result<()> {
-    struct MyUserData(i64);
-
-    impl UserData for MyUserData {
-        fn add_fields<'lua, F: UserDataFields<'lua, Self>>(fields: &mut F) {
-            fields.add_field("static", "constant");
-            fields.add_field_method_get("data", |_, this| Ok(this.0));
-            fields.add_field_method_set("data", |_, this, val| {
-                this.0 = val;
-                Ok(())
-            })
-        }
-    }
-
-    let lua = Lua::new();
-    let globals = lua.globals();
-
-    // Rc<T>
-    #[cfg(not(feature = "send"))]
-    {
-        let ud = Rc::new(MyUserData(1));
-        globals.set("rc_ud", ud.clone())?;
-        lua.load(
-            r#"
-            assert(rc_ud.static == "constant")
-            local ok, err = pcall(function() rc_ud.data = 2 end)
-            assert(
-                tostring(err):sub(1, 32) == "error mutably borrowing userdata",
-                "expected error mutably borrowing userdata, got " .. tostring(err)
-            )
-            assert(rc_ud.data == 1)
-        "#,
-        )
-        .exec()?;
-        globals.set("rc_ud", Nil)?;
-        lua.gc_collect()?;
-        assert_eq!(Rc::strong_count(&ud), 1);
-    }
-
-    // Rc<RefCell<T>>
-    #[cfg(not(feature = "send"))]
-    {
-        let ud = Rc::new(RefCell::new(MyUserData(1)));
-        globals.set("rc_refcell_ud", ud.clone())?;
-        lua.load(
-            r#"
-            assert(rc_refcell_ud.static == "constant")
-            rc_refcell_ud.data = rc_refcell_ud.data + 1
-            assert(rc_refcell_ud.data == 2)
-        "#,
-        )
-        .exec()?;
-        assert_eq!(ud.borrow().0, 2);
-        globals.set("rc_refcell_ud", Nil)?;
-        lua.gc_collect()?;
-        assert_eq!(Rc::strong_count(&ud), 1);
-    }
-
-    // Arc<T>
-    let ud1 = Arc::new(MyUserData(2));
-    globals.set("arc_ud", ud1.clone())?;
-    lua.load(
-        r#"
-        assert(arc_ud.static == "constant")
-        local ok, err = pcall(function() arc_ud.data = 3 end)
-        assert(
-            tostring(err):sub(1, 32) == "error mutably borrowing userdata",
-            "expected error mutably borrowing userdata, got " .. tostring(err)
-        )
-        assert(arc_ud.data == 2)
-    "#,
-    )
-    .exec()?;
-    globals.set("arc_ud", Nil)?;
-    lua.gc_collect()?;
-    assert_eq!(Arc::strong_count(&ud1), 1);
-
-    // Arc<Mutex<T>>
-    let ud2 = Arc::new(Mutex::new(MyUserData(2)));
-    globals.set("arc_mutex_ud", ud2.clone())?;
-    lua.load(
-        r#"
-        assert(arc_mutex_ud.static == "constant")
-        arc_mutex_ud.data = arc_mutex_ud.data + 1
-        assert(arc_mutex_ud.data == 3)
-    "#,
-    )
-    .exec()?;
-    #[cfg(not(feature = "parking_lot"))]
-    assert_eq!(ud2.lock().unwrap().0, 3);
-    #[cfg(feature = "parking_lot")]
-    assert_eq!(ud2.lock().0, 3);
-    globals.set("arc_mutex_ud", Nil)?;
-    lua.gc_collect()?;
-    assert_eq!(Arc::strong_count(&ud2), 1);
-
-    // Arc<RwLock<T>>
-    let ud3 = Arc::new(RwLock::new(MyUserData(3)));
-    globals.set("arc_rwlock_ud", ud3.clone())?;
-    lua.load(
-        r#"
-        assert(arc_rwlock_ud.static == "constant")
-        arc_rwlock_ud.data = arc_rwlock_ud.data + 1
-        assert(arc_rwlock_ud.data == 4)
-    "#,
-    )
-    .exec()?;
-    #[cfg(not(feature = "parking_lot"))]
-    assert_eq!(ud3.read().unwrap().0, 4);
-    #[cfg(feature = "parking_lot")]
-    assert_eq!(ud3.read().0, 4);
-    globals.set("arc_rwlock_ud", Nil)?;
-    lua.gc_collect()?;
-    assert_eq!(Arc::strong_count(&ud3), 1);
+    assert_eq!(metatable.get::<String>(MetaMethod::Type)?.to_str()?, "CustomName");
 
     Ok(())
 }
@@ -794,12 +640,12 @@ fn test_userdata_proxy() -> Result<()> {
     struct MyUserData(i64);
 
     impl UserData for MyUserData {
-        fn add_fields<'lua, F: UserDataFields<'lua, Self>>(fields: &mut F) {
+        fn add_fields<'a, F: UserDataFields<'a, Self>>(fields: &mut F) {
             fields.add_field("static_field", 123);
             fields.add_field_method_get("n", |_, this| Ok(this.0));
         }
 
-        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+        fn add_methods<'a, M: UserDataMethods<'a, Self>>(methods: &mut M) {
             methods.add_function("new", |_, n| Ok(Self(n)));
 
             methods.add_method("plus", |_, this, n: i64| Ok(this.0 + n));
@@ -867,8 +713,7 @@ fn test_any_userdata_wrap() -> Result<()> {
         reg.add_method("get", |_, this, ()| Ok(this.clone()));
     })?;
 
-    lua.globals()
-        .set("s", AnyUserData::wrap("hello".to_string()))?;
+    lua.globals().set("s", AnyUserData::wrap("hello".to_string()))?;
     lua.load(
         r#"
         assert(s:get() == "hello")
@@ -888,7 +733,7 @@ fn test_userdata_ext() -> Result<()> {
     struct MyUserData(u32);
 
     impl UserData for MyUserData {
-        fn add_fields<'lua, F: UserDataFields<'lua, Self>>(fields: &mut F) {
+        fn add_fields<'a, F: UserDataFields<'a, Self>>(fields: &mut F) {
             fields.add_field_method_get("n", |_, this| Ok(this.0));
             fields.add_field_method_set("n", |_, this, val| {
                 this.0 = val;
@@ -896,7 +741,7 @@ fn test_userdata_ext() -> Result<()> {
             });
         }
 
-        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+        fn add_methods<'a, M: UserDataMethods<'a, Self>>(methods: &mut M) {
             methods.add_meta_method(MetaMethod::Call, |_, _this, ()| Ok("called"));
             methods.add_method_mut("add", |_, this, x: u32| {
                 this.0 += x;
@@ -929,7 +774,7 @@ fn test_userdata_method_errors() -> Result<()> {
     struct MyUserData(i64);
 
     impl UserData for MyUserData {
-        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+        fn add_methods<'a, M: UserDataMethods<'a, Self>>(methods: &mut M) {
             methods.add_method("get_value", |_, data, ()| Ok(data.0));
         }
     }
@@ -967,25 +812,6 @@ fn test_userdata_pointer() -> Result<()> {
     Ok(())
 }
 
-#[cfg(all(feature = "unstable", not(feature = "send")))]
-#[test]
-fn test_owned_userdata() -> Result<()> {
-    let lua = Lua::new();
-
-    let ud = lua.create_any_userdata("abc")?.into_owned();
-    drop(lua);
-
-    assert_eq!(*ud.borrow::<&str>()?, "abc");
-    *ud.borrow_mut()? = "cba";
-    assert!(matches!(
-        ud.borrow::<i64>(),
-        Err(Error::UserDataTypeMismatch)
-    ));
-    assert_eq!(ud.take::<&str>()?, "cba");
-
-    Ok(())
-}
-
 #[cfg(feature = "macros")]
 #[test]
 fn test_userdata_derive() -> Result<()> {
@@ -1000,8 +826,7 @@ fn test_userdata_derive() -> Result<()> {
         reg.add_function("val", |_, this: MyUserData| Ok(this.0));
     })?;
 
-    lua.globals()
-        .set("ud", AnyUserData::wrap(MyUserData(123)))?;
+    lua.globals().set("ud", AnyUserData::wrap(MyUserData(123)))?;
     lua.load("assert(ud:val() == 123)").exec()?;
 
     // More complex struct where generics and where clause
@@ -1015,8 +840,7 @@ fn test_userdata_derive() -> Result<()> {
         reg.add_function("val", |_, this: MyUserData2<'static, i32>| Ok(*this.0));
     })?;
 
-    lua.globals()
-        .set("ud", AnyUserData::wrap(MyUserData2(&321)))?;
+    lua.globals().set("ud", AnyUserData::wrap(MyUserData2(&321)))?;
     lua.load("assert(ud:val() == 321)").exec()?;
 
     Ok(())

tests/value.rs

@@ -111,10 +111,7 @@ fn test_value_to_string() -> Result<()> {
         Value::Vector(mlua::Vector::new(10.0, 11.1, 12.2, 13.3)).to_string()?,
         "vector(10, 11.1, 12.2, 13.3)"
     );
-    assert_eq!(
-        Value::String(lua.create_string("hello")?).to_string()?,
-        "hello"
-    );
+    assert_eq!(Value::String(lua.create_string("hello")?).to_string()?, "hello");
 
     let table: Value = lua.load("{}").eval()?;
     assert!(table.to_string()?.starts_with("table:"));
@@ -140,7 +137,7 @@ fn test_value_to_string() -> Result<()> {
     let ud: Value = Value::UserData(lua.create_userdata(MyUserData)?);
     assert!(ud.to_string()?.starts_with("MyUserData:"));
 
-    let err = Value::Error(Error::runtime("test error"));
+    let err = Value::Error(Box::new(Error::runtime("test error")));
     assert_eq!(err.to_string()?, "runtime error: test error");
 
     Ok(())
@@ -189,9 +186,7 @@ fn test_value_conversions() -> Result<()> {
     assert_eq!(Value::Number(1.23).as_f64(), Some(1.23f64));
     assert!(Value::String(lua.create_string("hello")?).is_string());
     assert_eq!(
-        Value::String(lua.create_string("hello")?)
-            .as_string()
-            .unwrap(),
+        Value::String(lua.create_string("hello")?).as_string().unwrap(),
         "hello"
     );
     assert_eq!(
@@ -207,11 +202,9 @@ fn test_value_conversions() -> Result<()> {
     assert!(Value::Table(lua.create_table()?).is_table());
     assert!(Value::Table(lua.create_table()?).as_table().is_some());
     assert!(Value::Function(lua.create_function(|_, ()| Ok(())).unwrap()).is_function());
-    assert!(
-        Value::Function(lua.create_function(|_, ()| Ok(())).unwrap())
-            .as_function()
-            .is_some()
-    );
+    assert!(Value::Function(lua.create_function(|_, ()| Ok(())).unwrap())
+        .as_function()
+        .is_some());
     assert!(Value::Thread(lua.create_thread(lua.load("function() end").eval()?)?).is_thread());
     assert!(
         Value::Thread(lua.create_thread(lua.load("function() end").eval()?)?)