Stabilize async closures (RFC 3668)

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -511,9 +511,9 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
     );
     gate_all!(let_chains, "`let` expressions in this position are unstable");
     gate_all!(
-        async_closure,
-        "async closures are unstable",
-        "to use an async block, remove the `||`: `async {`"
+        async_trait_bounds,
+        "`async` trait bounds are unstable",
+        "use the desugared name of the async trait, such as `AsyncFn`"
     );
     gate_all!(async_for_loop, "`for await` loops are experimental");
     gate_all!(

compiler/rustc_error_codes/src/error_codes/E0708.md

@@ -5,8 +5,6 @@
 Erroneous code example:
 
 ```edition2018
-#![feature(async_closure)]
-
 fn main() {
     let add_one = async |num: u8| {
         num + 1
@@ -18,8 +16,6 @@ fn main() {
 version, you can use successfully by using move:
 
 ```edition2018
-#![feature(async_closure)]
-
 fn main() {
     let add_one = async move |num: u8| { // ok!
         num + 1

compiler/rustc_feature/src/accepted.rs

@@ -72,6 +72,8 @@ declare_features! (
     (accepted, associated_types, "1.0.0", None),
     /// Allows free and inherent `async fn`s, `async` blocks, and `<expr>.await` expressions.
     (accepted, async_await, "1.39.0", Some(50547)),
+    /// Allows `async || body` closures.
+    (accepted, async_closure, "CURRENT_RUSTC_VERSION", Some(62290)),
     /// Allows async functions to be declared, implemented, and used in traits.
     (accepted, async_fn_in_trait, "1.75.0", Some(91611)),
     /// Allows all literals in attribute lists and values of key-value pairs.

compiler/rustc_feature/src/unstable.rs

@@ -381,12 +381,12 @@ declare_features! (
     (unstable, associated_const_equality, "1.58.0", Some(92827)),
     /// Allows associated type defaults.
     (unstable, associated_type_defaults, "1.2.0", Some(29661)),
-    /// Allows `async || body` closures.
-    (unstable, async_closure, "1.37.0", Some(62290)),
     /// Allows `#[track_caller]` on async functions.
     (unstable, async_fn_track_caller, "1.73.0", Some(110011)),
     /// Allows `for await` loops.
     (unstable, async_for_loop, "1.77.0", Some(118898)),
+    /// Allows `async` trait bound modifier.
+    (unstable, async_trait_bounds, "CURRENT_RUSTC_VERSION", Some(62290)),
     /// Allows using C-variadics.
     (unstable, c_variadic, "1.34.0", Some(44930)),
     /// Allows the use of `#[cfg(<true/false>)]`.

compiler/rustc_hir_typeck/src/upvar.rs

@@ -1826,7 +1826,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 /// captured by move.
 ///
 /// ```rust
-/// #![feature(async_closure)]
 /// let x = &1i32; // Let's call this lifetime `'1`.
 /// let c = async move || {
 ///     println!("{:?}", *x);
@@ -1841,7 +1840,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 /// child capture with the lifetime of the parent coroutine-closure's env.
 ///
 /// ```rust
-/// #![feature(async_closure)]
 /// let mut x = 1i32;
 /// let c = async || {
 ///     x = 1;

compiler/rustc_lint/src/async_closures.rs

@@ -12,7 +12,6 @@ declare_lint! {
     /// ### Example
     ///
     /// ```rust
-    /// #![feature(async_closure)]
     /// #![warn(closure_returning_async_block)]
     /// let c = |x: &str| async {};
     /// ```
@@ -40,8 +39,6 @@ declare_lint! {
     /// But it does work with async closures:
     ///
     /// ```rust
-    /// #![feature(async_closure)]
-    ///
     /// async fn callback(x: &str) {}
     ///
     /// let captured_str = String::new();
@@ -52,7 +49,6 @@ declare_lint! {
     pub CLOSURE_RETURNING_ASYNC_BLOCK,
     Allow,
     "closure that returns `async {}` could be rewritten as an async closure",
-    @feature_gate = async_closure;
 }
 
 declare_lint_pass!(

compiler/rustc_mir_transform/src/coroutine/by_move_body.rs

@@ -3,8 +3,6 @@
 //!
 //! Consider an async closure like:
 //! ```rust
-//! #![feature(async_closure)]
-//!
 //! let x = vec![1, 2, 3];
 //!
 //! let closure = async move || {

compiler/rustc_parse/src/parser/expr.rs

@@ -2362,10 +2362,7 @@ impl<'a> Parser<'a> {
         };
 
         match coroutine_kind {
-            Some(CoroutineKind::Async { span, .. }) => {
-                // Feature-gate `async ||` closures.
-                self.psess.gated_spans.gate(sym::async_closure, span);
-            }
+            Some(CoroutineKind::Async { .. }) => {}
             Some(CoroutineKind::Gen { span, .. }) | Some(CoroutineKind::AsyncGen { span, .. }) => {
                 // Feature-gate `gen ||` and `async gen ||` closures.
                 // FIXME(gen_blocks): This perhaps should be a different gate.

compiler/rustc_parse/src/parser/ty.rs

@@ -943,7 +943,7 @@ impl<'a> Parser<'a> {
         let asyncness = if self.token.uninterpolated_span().at_least_rust_2018()
             && self.eat_keyword(kw::Async)
         {
-            self.psess.gated_spans.gate(sym::async_closure, self.prev_token.span);
+            self.psess.gated_spans.gate(sym::async_trait_bounds, self.prev_token.span);
             BoundAsyncness::Async(self.prev_token.span)
         } else if self.may_recover()
             && self.token.uninterpolated_span().is_rust_2015()
@@ -954,7 +954,7 @@ impl<'a> Parser<'a> {
                 span: self.prev_token.span,
                 help: HelpUseLatestEdition::new(),
             });
-            self.psess.gated_spans.gate(sym::async_closure, self.prev_token.span);
+            self.psess.gated_spans.gate(sym::async_trait_bounds, self.prev_token.span);
             BoundAsyncness::Async(self.prev_token.span)
         } else {
             BoundAsyncness::Normal

compiler/rustc_span/src/symbol.rs

@@ -464,6 +464,7 @@ symbols! {
         async_for_loop,
         async_iterator,
         async_iterator_poll_next,
+        async_trait_bounds,
         atomic,
         atomic_mod,
         atomics,

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -794,7 +794,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     closure_def_id,
                     found_kind,
                     expected_kind,
-                    "async ",
+                    "Async",
                 );
                 self.note_obligation_cause(&mut err, &obligation);
                 self.point_at_returns_when_relevant(&mut err, &obligation);

library/alloc/src/boxed.rs

@@ -1982,7 +1982,8 @@ impl<Args: Tuple, F: Fn<Args> + ?Sized, A: Allocator> Fn<Args> for Box<F, A> {
     }
 }
 
-#[unstable(feature = "async_fn_traits", issue = "none")]
+#[cfg_attr(bootstrap, unstable(feature = "async_closure", issue = "62290"))]
+#[cfg_attr(not(bootstrap), stable(feature = "async_closure", since = "CURRENT_RUSTC_VERSION"))]
 impl<Args: Tuple, F: AsyncFnOnce<Args> + ?Sized, A: Allocator> AsyncFnOnce<Args> for Box<F, A> {
     type Output = F::Output;
     type CallOnceFuture = F::CallOnceFuture;
@@ -1992,7 +1993,8 @@ impl<Args: Tuple, F: AsyncFnOnce<Args> + ?Sized, A: Allocator> AsyncFnOnce<Args>
     }
 }
 
-#[unstable(feature = "async_fn_traits", issue = "none")]
+#[cfg_attr(bootstrap, unstable(feature = "async_closure", issue = "62290"))]
+#[cfg_attr(not(bootstrap), stable(feature = "async_closure", since = "CURRENT_RUSTC_VERSION"))]
 impl<Args: Tuple, F: AsyncFnMut<Args> + ?Sized, A: Allocator> AsyncFnMut<Args> for Box<F, A> {
     type CallRefFuture<'a>
         = F::CallRefFuture<'a>
@@ -2004,7 +2006,8 @@ impl<Args: Tuple, F: AsyncFnMut<Args> + ?Sized, A: Allocator> AsyncFnMut<Args> f
     }
 }
 
-#[unstable(feature = "async_fn_traits", issue = "none")]
+#[cfg_attr(bootstrap, unstable(feature = "async_closure", issue = "62290"))]
+#[cfg_attr(not(bootstrap), stable(feature = "async_closure", since = "CURRENT_RUSTC_VERSION"))]
 impl<Args: Tuple, F: AsyncFn<Args> + ?Sized, A: Allocator> AsyncFn<Args> for Box<F, A> {
     extern "rust-call" fn async_call(&self, args: Args) -> Self::CallRefFuture<'_> {
         F::async_call(self, args)

library/alloc/src/lib.rs

@@ -91,6 +91,7 @@
 //
 // Library features:
 // tidy-alphabetical-start
+#![cfg_attr(bootstrap, feature(async_closure))]
 #![cfg_attr(not(no_global_oom_handling), feature(const_alloc_error))]
 #![cfg_attr(not(no_global_oom_handling), feature(const_btree_len))]
 #![cfg_attr(test, feature(str_as_str))]
@@ -101,7 +102,6 @@
 #![feature(array_windows)]
 #![feature(ascii_char)]
 #![feature(assert_matches)]
-#![feature(async_closure)]
 #![feature(async_fn_traits)]
 #![feature(async_iterator)]
 #![feature(box_uninit_write)]

library/core/src/ops/async_function.rs

@@ -4,7 +4,8 @@ use crate::marker::Tuple;
 /// An async-aware version of the [`Fn`](crate::ops::Fn) trait.
 ///
 /// All `async fn` and functions returning futures implement this trait.
-#[unstable(feature = "async_closure", issue = "62290")]
+#[cfg_attr(bootstrap, unstable(feature = "async_closure", issue = "62290"))]
+#[cfg_attr(not(bootstrap), stable(feature = "async_closure", since = "CURRENT_RUSTC_VERSION"))]
 #[rustc_paren_sugar]
 #[fundamental]
 #[must_use = "async closures are lazy and do nothing unless called"]
@@ -18,7 +19,8 @@ pub trait AsyncFn<Args: Tuple>: AsyncFnMut<Args> {
 /// An async-aware version of the [`FnMut`](crate::ops::FnMut) trait.
 ///
 /// All `async fn` and functions returning futures implement this trait.
-#[unstable(feature = "async_closure", issue = "62290")]
+#[cfg_attr(bootstrap, unstable(feature = "async_closure", issue = "62290"))]
+#[cfg_attr(not(bootstrap), stable(feature = "async_closure", since = "CURRENT_RUSTC_VERSION"))]
 #[rustc_paren_sugar]
 #[fundamental]
 #[must_use = "async closures are lazy and do nothing unless called"]
@@ -39,7 +41,8 @@ pub trait AsyncFnMut<Args: Tuple>: AsyncFnOnce<Args> {
 /// An async-aware version of the [`FnOnce`](crate::ops::FnOnce) trait.
 ///
 /// All `async fn` and functions returning futures implement this trait.
-#[unstable(feature = "async_closure", issue = "62290")]
+#[cfg_attr(bootstrap, unstable(feature = "async_closure", issue = "62290"))]
+#[cfg_attr(not(bootstrap), stable(feature = "async_closure", since = "CURRENT_RUSTC_VERSION"))]
 #[rustc_paren_sugar]
 #[fundamental]
 #[must_use = "async closures are lazy and do nothing unless called"]
@@ -64,7 +67,8 @@ mod impls {
     use super::{AsyncFn, AsyncFnMut, AsyncFnOnce};
     use crate::marker::Tuple;
 
-    #[unstable(feature = "async_fn_traits", issue = "none")]
+    #[cfg_attr(bootstrap, unstable(feature = "async_closure", issue = "62290"))]
+    #[cfg_attr(not(bootstrap), stable(feature = "async_closure", since = "CURRENT_RUSTC_VERSION"))]
     impl<A: Tuple, F: ?Sized> AsyncFn<A> for &F
     where
         F: AsyncFn<A>,
@@ -74,7 +78,8 @@ mod impls {
         }
     }
 
-    #[unstable(feature = "async_fn_traits", issue = "none")]
+    #[cfg_attr(bootstrap, unstable(feature = "async_closure", issue = "62290"))]
+    #[cfg_attr(not(bootstrap), stable(feature = "async_closure", since = "CURRENT_RUSTC_VERSION"))]
     impl<A: Tuple, F: ?Sized> AsyncFnMut<A> for &F
     where
         F: AsyncFn<A>,
@@ -89,7 +94,8 @@ mod impls {
         }
     }
 
-    #[unstable(feature = "async_fn_traits", issue = "none")]
+    #[cfg_attr(bootstrap, unstable(feature = "async_closure", issue = "62290"))]
+    #[cfg_attr(not(bootstrap), stable(feature = "async_closure", since = "CURRENT_RUSTC_VERSION"))]
     impl<'a, A: Tuple, F: ?Sized> AsyncFnOnce<A> for &'a F
     where
         F: AsyncFn<A>,
@@ -102,7 +108,8 @@ mod impls {
         }
     }
 
-    #[unstable(feature = "async_fn_traits", issue = "none")]
+    #[cfg_attr(bootstrap, unstable(feature = "async_closure", issue = "62290"))]
+    #[cfg_attr(not(bootstrap), stable(feature = "async_closure", since = "CURRENT_RUSTC_VERSION"))]
     impl<A: Tuple, F: ?Sized> AsyncFnMut<A> for &mut F
     where
         F: AsyncFnMut<A>,
@@ -117,7 +124,8 @@ mod impls {
         }
     }
 
-    #[unstable(feature = "async_fn_traits", issue = "none")]
+    #[cfg_attr(bootstrap, unstable(feature = "async_closure", issue = "62290"))]
+    #[cfg_attr(not(bootstrap), stable(feature = "async_closure", since = "CURRENT_RUSTC_VERSION"))]
     impl<'a, A: Tuple, F: ?Sized> AsyncFnOnce<A> for &'a mut F
     where
         F: AsyncFnMut<A>,

library/std/src/prelude/common.rs

@@ -12,6 +12,10 @@ pub use crate::marker::{Send, Sized, Sync, Unpin};
 #[stable(feature = "rust1", since = "1.0.0")]
 #[doc(no_inline)]
 pub use crate::ops::{Drop, Fn, FnMut, FnOnce};
+#[cfg_attr(bootstrap, unstable(feature = "async_closure", issue = "62290"))]
+#[cfg_attr(not(bootstrap), stable(feature = "async_closure", since = "CURRENT_RUSTC_VERSION"))]
+#[doc(no_inline)]
+pub use crate::ops::{AsyncFn, AsyncFnMut, AsyncFnOnce};
 
 // Re-exported functions
 #[stable(feature = "rust1", since = "1.0.0")]

src/tools/clippy/tests/ui-internal/author/blocks.rs

@@ -2,7 +2,6 @@
 
 #![allow(redundant_semicolons, clippy::no_effect)]
 #![feature(stmt_expr_attributes)]
-#![feature(async_closure)]
 
 #[rustfmt::skip]
 fn main() {

src/tools/clippy/tests/ui/async_yields_async.fixed

@@ -1,4 +1,3 @@
-#![feature(async_closure)]
 #![warn(clippy::async_yields_async)]
 #![allow(clippy::redundant_async_block)]
 

src/tools/clippy/tests/ui/async_yields_async.rs

@@ -1,4 +1,3 @@
-#![feature(async_closure)]
 #![warn(clippy::async_yields_async)]
 #![allow(clippy::redundant_async_block)]
 

src/tools/clippy/tests/ui/async_yields_async.stderr

@@ -1,5 +1,5 @@
 error: an async construct yields a type which is itself awaitable
-  --> tests/ui/async_yields_async.rs:38:9
+  --> tests/ui/async_yields_async.rs:37:9
    |
 LL |        let _h = async {
    |  _____________________-
@@ -20,7 +20,7 @@ LL +         }.await
    |
 
 error: an async construct yields a type which is itself awaitable
-  --> tests/ui/async_yields_async.rs:43:9
+  --> tests/ui/async_yields_async.rs:42:9
    |
 LL |       let _i = async {
    |  ____________________-
@@ -33,7 +33,7 @@ LL | |     };
    | |_____- outer async construct
 
 error: an async construct yields a type which is itself awaitable
-  --> tests/ui/async_yields_async.rs:49:9
+  --> tests/ui/async_yields_async.rs:48:9
    |
 LL |        let _j = async || {
    |  ________________________-
@@ -52,7 +52,7 @@ LL +         }.await
    |
 
 error: an async construct yields a type which is itself awaitable
-  --> tests/ui/async_yields_async.rs:54:9
+  --> tests/ui/async_yields_async.rs:53:9
    |
 LL |       let _k = async || {
    |  _______________________-
@@ -65,7 +65,7 @@ LL | |     };
    | |_____- outer async construct
 
 error: an async construct yields a type which is itself awaitable
-  --> tests/ui/async_yields_async.rs:56:23
+  --> tests/ui/async_yields_async.rs:55:23
    |
 LL |     let _l = async || CustomFutureType;
    |                       ^^^^^^^^^^^^^^^^
@@ -75,7 +75,7 @@ LL |     let _l = async || CustomFutureType;
    |                       help: consider awaiting this value: `CustomFutureType.await`
 
 error: an async construct yields a type which is itself awaitable
-  --> tests/ui/async_yields_async.rs:62:9
+  --> tests/ui/async_yields_async.rs:61:9
    |
 LL |       let _m = async || {
    |  _______________________-

src/tools/clippy/tests/ui/redundant_closure_call_fixable.fixed

@@ -1,4 +1,3 @@
-#![feature(async_closure)]
 #![warn(clippy::redundant_closure_call)]
 #![allow(clippy::redundant_async_block)]
 #![allow(clippy::type_complexity)]

src/tools/clippy/tests/ui/redundant_closure_call_fixable.rs

@@ -1,4 +1,3 @@
-#![feature(async_closure)]
 #![warn(clippy::redundant_closure_call)]
 #![allow(clippy::redundant_async_block)]
 #![allow(clippy::type_complexity)]