diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index a0a63620c08a9..d3fc6e9e25158 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -593,7 +593,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
/// Desugar `<expr>.await` into:
/// ```rust
- /// match <expr> {
+ /// match ::std::future::IntoFuture::into_future(<expr>) {
/// mut pinned => loop {
/// match unsafe { ::std::future::Future::poll(
/// <::std::pin::Pin>::new_unchecked(&mut pinned),
@@ -629,7 +629,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
await_span,
self.allow_gen_future.clone(),
);
- let expr = self.lower_expr(expr);
+ let expr = self.lower_expr_mut(expr);
let pinned_ident = Ident::with_dummy_span(sym::pinned);
let (pinned_pat, pinned_pat_hid) =
@@ -746,10 +746,26 @@ impl<'hir> LoweringContext<'_, 'hir> {
// mut pinned => loop { ... }
let pinned_arm = self.arm(pinned_pat, loop_expr);
- // match <expr> {
+ // `match ::std::future::IntoFuture::into_future(<expr>) { ... }`
+ let into_future_span = self.mark_span_with_reason(
+ DesugaringKind::Await,
+ await_span,
+ self.allow_into_future.clone(),
+ );
+ let into_future_expr = self.expr_call_lang_item_fn(
+ into_future_span,
+ hir::LangItem::IntoFutureIntoFuture,
+ arena_vec![self; expr],
+ );
+
+ // match <into_future_expr> {
// mut pinned => loop { .. }
// }
- hir::ExprKind::Match(expr, arena_vec![self; pinned_arm], hir::MatchSource::AwaitDesugar)
+ hir::ExprKind::Match(
+ into_future_expr,
+ arena_vec![self; pinned_arm],
+ hir::MatchSource::AwaitDesugar,
+ )
}
fn lower_expr_closure(
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 2b3a538772ecb..f5aafda9297a5 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -162,6 +162,7 @@ struct LoweringContext<'a, 'hir: 'a> {
allow_try_trait: Option<Lrc<[Symbol]>>,
allow_gen_future: Option<Lrc<[Symbol]>>,
+ allow_into_future: Option<Lrc<[Symbol]>>,
}
pub trait ResolverAstLowering {
@@ -320,6 +321,7 @@ pub fn lower_crate<'a, 'hir>(
in_scope_lifetimes: Vec::new(),
allow_try_trait: Some([sym::try_trait_v2][..].into()),
allow_gen_future: Some([sym::gen_future][..].into()),
+ allow_into_future: Some([sym::into_future][..].into()),
}
.lower_crate(krate)
}
diff --git a/compiler/rustc_hir/src/lang_items.rs b/compiler/rustc_hir/src/lang_items.rs
index 3037996d48bc0..32c6d54497c4d 100644
--- a/compiler/rustc_hir/src/lang_items.rs
+++ b/compiler/rustc_hir/src/lang_items.rs
@@ -347,6 +347,7 @@ language_item_table! {
ControlFlowContinue, sym::Continue, cf_continue_variant, Target::Variant, GenericRequirement::None;
ControlFlowBreak, sym::Break, cf_break_variant, Target::Variant, GenericRequirement::None;
+ IntoFutureIntoFuture, sym::into_future, into_future_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
IntoIterIntoIter, sym::into_iter, into_iter_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
IteratorNext, sym::next, next_fn, Target::Method(MethodKind::Trait { body: false}), GenericRequirement::None;
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 0d556b5eda609..774ae3164c8d8 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -196,6 +196,7 @@ symbols! {
Implied,
Input,
Into,
+ IntoFuture,
IntoIterator,
IoRead,
IoWrite,
@@ -734,6 +735,7 @@ symbols! {
inout,
instruction_set,
intel,
+ into_future,
into_iter,
intra_doc_pointers,
intrinsics,
diff --git a/library/core/src/future/future.rs b/library/core/src/future/future.rs
index 09d8a2aac26e9..6b62236b32faf 100644
--- a/library/core/src/future/future.rs
+++ b/library/core/src/future/future.rs
@@ -28,7 +28,11 @@ use crate::task::{Context, Poll};
#[must_use = "futures do nothing unless you `.await` or poll them"]
#[stable(feature = "futures_api", since = "1.36.0")]
#[lang = "future_trait"]
-#[rustc_on_unimplemented(label = "`{Self}` is not a future", message = "`{Self}` is not a future")]
+#[rustc_on_unimplemented(
+ label = "`{Self}` is not a future",
+ message = "`{Self}` is not a future",
+ note = "{Self} must be a future or must implement `IntoFuture` to be awaited"
+)]
pub trait Future {
/// The type of value produced on completion.
#[stable(feature = "futures_api", since = "1.36.0")]
diff --git a/library/core/src/future/into_future.rs b/library/core/src/future/into_future.rs
index 4020c254446e3..cac1866188eff 100644
--- a/library/core/src/future/into_future.rs
+++ b/library/core/src/future/into_future.rs
@@ -13,6 +13,7 @@ pub trait IntoFuture {
/// Creates a future from a value.
#[unstable(feature = "into_future", issue = "67644")]
+ #[cfg_attr(not(bootstrap), lang = "into_future")]
fn into_future(self) -> Self::Future;
}
diff --git a/src/test/ui/async-await/async-error-span.stderr b/src/test/ui/async-await/async-error-span.stderr
index 994bfd33ba42e..2e3f8bb52560a 100644
--- a/src/test/ui/async-await/async-error-span.stderr
+++ b/src/test/ui/async-await/async-error-span.stderr
@@ -5,6 +5,7 @@ LL | fn get_future() -> impl Future<Output = ()> {
| ^^^^^^^^^^^^^^^^^^^^^^^^ `()` is not a future
|
= help: the trait `Future` is not implemented for `()`
+ = note: () must be a future or must implement `IntoFuture` to be awaited
error[E0698]: type inside `async fn` body must be known in this context
--> $DIR/async-error-span.rs:13:9
diff --git a/src/test/ui/async-await/async-fn-size-moved-locals.rs b/src/test/ui/async-await/async-fn-size-moved-locals.rs
index 636fafc2bc44a..a603ebd6e8547 100644
--- a/src/test/ui/async-await/async-fn-size-moved-locals.rs
+++ b/src/test/ui/async-await/async-fn-size-moved-locals.rs
@@ -112,7 +112,7 @@ async fn mixed_sizes() {
fn main() {
assert_eq!(1025, std::mem::size_of_val(&single()));
assert_eq!(1026, std::mem::size_of_val(&single_with_noop()));
- assert_eq!(3078, std::mem::size_of_val(&joined()));
- assert_eq!(3079, std::mem::size_of_val(&joined_with_noop()));
- assert_eq!(7181, std::mem::size_of_val(&mixed_sizes()));
+ assert_eq!(3076, std::mem::size_of_val(&joined()));
+ assert_eq!(3076, std::mem::size_of_val(&joined_with_noop()));
+ assert_eq!(6157, std::mem::size_of_val(&mixed_sizes()));
}
diff --git a/src/test/ui/async-await/await-into-future.rs b/src/test/ui/async-await/await-into-future.rs
new file mode 100644
index 0000000000000..b74b168444085
--- /dev/null
+++ b/src/test/ui/async-await/await-into-future.rs
@@ -0,0 +1,30 @@
+// run-pass
+// aux-build: issue-72470-lib.rs
+// edition:2021
+#![feature(into_future)]
+
+extern crate issue_72470_lib;
+use std::{future::{Future, IntoFuture}, pin::Pin};
+
+struct AwaitMe;
+
+impl IntoFuture for AwaitMe {
+ type Output = i32;
+ type Future = Pin<Box<dyn Future<Output = i32>>>;
+
+ fn into_future(self) -> Self::Future {
+ Box::pin(me())
+ }
+}
+
+async fn me() -> i32 {
+ 41
+}
+
+async fn run() {
+ assert_eq!(AwaitMe.await, 41);
+}
+
+fn main() {
+ issue_72470_lib::run(run());
+}
diff --git a/src/test/ui/async-await/issue-70594.stderr b/src/test/ui/async-await/issue-70594.stderr
index eb24040404b90..ab05251526b0d 100644
--- a/src/test/ui/async-await/issue-70594.stderr
+++ b/src/test/ui/async-await/issue-70594.stderr
@@ -25,6 +25,8 @@ LL | [1; ().await];
| ^^^^^^^^ `()` is not a future
|
= help: the trait `Future` is not implemented for `()`
+ = note: () must be a future or must implement `IntoFuture` to be awaited
+ = note: required because of the requirements on the impl of `IntoFuture` for `()`
error: aborting due to 4 previous errors
diff --git a/src/test/ui/async-await/issues/issue-62009-1.stderr b/src/test/ui/async-await/issues/issue-62009-1.stderr
index e2ea72a1e6178..19d6f9bc43866 100644
--- a/src/test/ui/async-await/issues/issue-62009-1.stderr
+++ b/src/test/ui/async-await/issues/issue-62009-1.stderr
@@ -34,6 +34,8 @@ LL | (|_| 2333).await;
| ^^^^^^^^^^^^^^^^ `[closure@$DIR/issue-62009-1.rs:12:5: 12:15]` is not a future
|
= help: the trait `Future` is not implemented for `[closure@$DIR/issue-62009-1.rs:12:5: 12:15]`
+ = note: [closure@$DIR/issue-62009-1.rs:12:5: 12:15] must be a future or must implement `IntoFuture` to be awaited
+ = note: required because of the requirements on the impl of `IntoFuture` for `[closure@$DIR/issue-62009-1.rs:12:5: 12:15]`
error: aborting due to 4 previous errors
diff --git a/src/test/ui/async-await/unresolved_type_param.rs b/src/test/ui/async-await/unresolved_type_param.rs
index d313691b38857..85d868c27032e 100644
--- a/src/test/ui/async-await/unresolved_type_param.rs
+++ b/src/test/ui/async-await/unresolved_type_param.rs
@@ -10,12 +10,20 @@ async fn foo() {
//~^ ERROR type inside `async fn` body must be known in this context
//~| ERROR type inside `async fn` body must be known in this context
//~| ERROR type inside `async fn` body must be known in this context
+ //~| ERROR type inside `async fn` body must be known in this context
+ //~| ERROR type inside `async fn` body must be known in this context
+ //~| NOTE cannot infer type for type parameter `T`
+ //~| NOTE cannot infer type for type parameter `T`
//~| NOTE cannot infer type for type parameter `T`
//~| NOTE cannot infer type for type parameter `T`
//~| NOTE cannot infer type for type parameter `T`
//~| NOTE the type is part of the `async fn` body because of this `await`
//~| NOTE the type is part of the `async fn` body because of this `await`
//~| NOTE the type is part of the `async fn` body because of this `await`
+ //~| NOTE the type is part of the `async fn` body because of this `await`
+ //~| NOTE the type is part of the `async fn` body because of this `await`
+ //~| NOTE in this expansion of desugaring of `await`
+ //~| NOTE in this expansion of desugaring of `await`
//~| NOTE in this expansion of desugaring of `await`
//~| NOTE in this expansion of desugaring of `await`
//~| NOTE in this expansion of desugaring of `await`
diff --git a/src/test/ui/async-await/unresolved_type_param.stderr b/src/test/ui/async-await/unresolved_type_param.stderr
index 6b9e960ca1ae6..130667a49c53a 100644
--- a/src/test/ui/async-await/unresolved_type_param.stderr
+++ b/src/test/ui/async-await/unresolved_type_param.stderr
@@ -34,6 +34,30 @@ note: the type is part of the `async fn` body because of this `await`
LL | bar().await;
| ^^^^^^^^^^^
-error: aborting due to 3 previous errors
+error[E0698]: type inside `async fn` body must be known in this context
+ --> $DIR/unresolved_type_param.rs:9:5
+ |
+LL | bar().await;
+ | ^^^ cannot infer type for type parameter `T` declared on the function `bar`
+ |
+note: the type is part of the `async fn` body because of this `await`
+ --> $DIR/unresolved_type_param.rs:9:5
+ |
+LL | bar().await;
+ | ^^^^^^^^^^^
+
+error[E0698]: type inside `async fn` body must be known in this context
+ --> $DIR/unresolved_type_param.rs:9:5
+ |
+LL | bar().await;
+ | ^^^ cannot infer type for type parameter `T` declared on the function `bar`
+ |
+note: the type is part of the `async fn` body because of this `await`
+ --> $DIR/unresolved_type_param.rs:9:5
+ |
+LL | bar().await;
+ | ^^^^^^^^^^^
+
+error: aborting due to 5 previous errors
For more information about this error, try `rustc --explain E0698`.
diff --git a/src/test/ui/issues-71798.stderr b/src/test/ui/issues-71798.stderr
index bbcdd3e37a96e..bc4dc9ebf9e00 100644
--- a/src/test/ui/issues-71798.stderr
+++ b/src/test/ui/issues-71798.stderr
@@ -11,6 +11,7 @@ LL | fn test_ref(x: &u32) -> impl std::future::Future<Output = u32> + '_ {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `u32` is not a future
|
= help: the trait `Future` is not implemented for `u32`
+ = note: u32 must be a future or must implement `IntoFuture` to be awaited
error: aborting due to 2 previous errors
diff --git a/src/test/ui/suggestions/async-fn-ctor-passed-as-arg-where-it-should-have-been-called.stderr b/src/test/ui/suggestions/async-fn-ctor-passed-as-arg-where-it-should-have-been-called.stderr
index 4759ebea0e9b7..766db2a8356e7 100644
--- a/src/test/ui/suggestions/async-fn-ctor-passed-as-arg-where-it-should-have-been-called.stderr
+++ b/src/test/ui/suggestions/async-fn-ctor-passed-as-arg-where-it-should-have-been-called.stderr
@@ -10,6 +10,7 @@ LL | bar(foo);
| required by a bound introduced by this call
|
= help: the trait `Future` is not implemented for `fn() -> impl Future<Output = ()> {foo}`
+ = note: fn() -> impl Future<Output = ()> {foo} must be a future or must implement `IntoFuture` to be awaited
note: required by a bound in `bar`
--> $DIR/async-fn-ctor-passed-as-arg-where-it-should-have-been-called.rs:7:16
|
@@ -31,6 +32,7 @@ LL | bar(async_closure);
| required by a bound introduced by this call
|
= help: the trait `Future` is not implemented for `[closure@$DIR/async-fn-ctor-passed-as-arg-where-it-should-have-been-called.rs:11:25: 11:36]`
+ = note: [closure@$DIR/async-fn-ctor-passed-as-arg-where-it-should-have-been-called.rs:11:25: 11:36] must be a future or must implement `IntoFuture` to be awaited
note: required by a bound in `bar`
--> $DIR/async-fn-ctor-passed-as-arg-where-it-should-have-been-called.rs:7:16
|