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Support async trait bounds in macros
1 parent 29f87ad commit 9c8b107

16 files changed

+228
-30
lines changed

‎compiler/rustc_parse/messages.ftl

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@@ -27,6 +27,8 @@ parse_async_bound_modifier_in_2015 = `async` trait bounds are only allowed in Ru
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parse_async_fn_in_2015 = `async fn` is not permitted in Rust 2015
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.label = to use `async fn`, switch to Rust 2018 or later
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parse_async_impl = `async` trait implementations are unsupported
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parse_async_move_block_in_2015 = `async move` blocks are only allowed in Rust 2018 or later
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parse_async_move_order_incorrect = the order of `move` and `async` is incorrect

‎compiler/rustc_parse/src/errors.rs

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@@ -2975,3 +2975,10 @@ pub(crate) struct ArrayIndexInOffsetOf(#[primary_span] pub Span);
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#[derive(Diagnostic)]
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#[diag(parse_invalid_offset_of)]
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pub(crate) struct InvalidOffsetOf(#[primary_span] pub Span);
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#[derive(Diagnostic)]
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#[diag(parse_async_impl)]
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pub(crate) struct AsyncImpl {
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#[primary_span]
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pub span: Span,
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}

‎compiler/rustc_parse/src/parser/item.rs

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@@ -562,6 +562,15 @@ impl<'a> Parser<'a> {
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self.sess.gated_spans.gate(sym::const_trait_impl, span);
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}
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// Parse stray `impl async Trait`
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if (self.token.uninterpolated_span().at_least_rust_2018()
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&& self.token.is_keyword(kw::Async))
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|| self.is_kw_followed_by_ident(kw::Async)
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{
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self.bump();
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self.dcx().emit_err(errors::AsyncImpl { span: self.prev_token.span });
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}
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let polarity = self.parse_polarity();
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// Parse both types and traits as a type, then reinterpret if necessary.

‎compiler/rustc_parse/src/parser/ty.rs

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@@ -778,9 +778,10 @@ impl<'a> Parser<'a> {
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|| self.check(&token::Not)
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|| self.check(&token::Question)
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|| self.check(&token::Tilde)
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|| self.check_keyword(kw::Const)
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|| self.check_keyword(kw::For)
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|| self.check(&token::OpenDelim(Delimiter::Parenthesis))
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|| self.check_keyword(kw::Const)
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|| self.check_keyword(kw::Async)
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}
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/// Parses a bound according to the grammar:
@@ -882,11 +883,13 @@ impl<'a> Parser<'a> {
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BoundConstness::Never
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};
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let asyncness = if self.token.span.at_least_rust_2018() && self.eat_keyword(kw::Async) {
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let asyncness = if self.token.uninterpolated_span().at_least_rust_2018()
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&& self.eat_keyword(kw::Async)
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{
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self.sess.gated_spans.gate(sym::async_closure, self.prev_token.span);
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BoundAsyncness::Async(self.prev_token.span)
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} else if self.may_recover()
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&& self.token.span.is_rust_2015()
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&& self.token.uninterpolated_span().is_rust_2015()
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&& self.is_kw_followed_by_ident(kw::Async)
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{
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self.bump(); // eat `async`

‎tests/ui/async-await/async-fn/impl-header.rs

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@@ -3,6 +3,10 @@
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struct F;
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impl async Fn<()> for F {}
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//~^ ERROR expected type, found keyword `async`
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//~^ ERROR `async` trait implementations are unsupported
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//~| ERROR the precise format of `Fn`-family traits' type parameters is subject to change
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//~| ERROR manual implementations of `Fn` are experimental
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//~| ERROR expected a `FnMut()` closure, found `F`
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//~| ERROR not all trait items implemented, missing: `call`
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fn main() {}

‎tests/ui/async-await/async-fn/impl-header.stderr

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@@ -1,8 +1,47 @@
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error: expected type, found keyword `async`
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error: `async` trait implementations are unsupported
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--> $DIR/impl-header.rs:5:6
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|
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LL | impl async Fn<()> for F {}
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| ^^^^^ expected type
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| ^^^^^
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error: aborting due to 1 previous error
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error[E0658]: the precise format of `Fn`-family traits' type parameters is subject to change
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--> $DIR/impl-header.rs:5:12
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|
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LL | impl async Fn<()> for F {}
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| ^^^^^^
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|
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= note: see issue #29625 <https://github.com/rust-lang/rust/issues/29625> for more information
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= help: add `#![feature(unboxed_closures)]` to the crate attributes to enable
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= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
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error[E0183]: manual implementations of `Fn` are experimental
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--> $DIR/impl-header.rs:5:12
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|
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LL | impl async Fn<()> for F {}
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| ^^^^^^ manual implementations of `Fn` are experimental
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|
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= help: add `#![feature(unboxed_closures)]` to the crate attributes to enable
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error[E0277]: expected a `FnMut()` closure, found `F`
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--> $DIR/impl-header.rs:5:23
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|
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LL | impl async Fn<()> for F {}
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| ^ expected an `FnMut()` closure, found `F`
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|
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= help: the trait `FnMut<()>` is not implemented for `F`
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= note: wrap the `F` in a closure with no arguments: `|| { /* code */ }`
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note: required by a bound in `Fn`
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--> $SRC_DIR/core/src/ops/function.rs:LL:COL
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error[E0046]: not all trait items implemented, missing: `call`
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--> $DIR/impl-header.rs:5:1
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|
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LL | impl async Fn<()> for F {}
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| ^^^^^^^^^^^^^^^^^^^^^^^ missing `call` in implementation
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|
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= help: implement the missing item: `fn call(&self, _: ()) -> <Self as FnOnce<()>>::Output { todo!() }`
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error: aborting due to 5 previous errors
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Some errors have detailed explanations: E0046, E0183, E0277, E0658.
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For more information about an error, try `rustc --explain E0046`.

‎tests/ui/async-await/async-fn/mbe-async-trait-bound-theoretical-regression.rs

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@@ -0,0 +1,21 @@
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// Demonstrates and records a theoretical regressions / breaking changes caused by the
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// introduction of async trait bounds.
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// Setting the edition to 2018 since we don't regress `demo! { dyn async }` in Rust <2018.
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//@ edition:2018
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macro_rules! demo {
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($ty:ty) => { compile_error!("ty"); };
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//~^ ERROR ty
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//~| ERROR ty
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(impl $c:ident Trait) => {};
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(dyn $c:ident Trait) => {};
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}
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demo! { impl async Trait }
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//~^ ERROR async closures are unstable
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demo! { dyn async Trait }
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//~^ ERROR async closures are unstable
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fn main() {}

‎tests/ui/async-await/async-fn/mbe-async-trait-bound-theoretical-regression.stderr

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@@ -0,0 +1,47 @@
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error: ty
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--> $DIR/mbe-async-trait-bound-theoretical-regression.rs:8:19
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|
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LL | ($ty:ty) => { compile_error!("ty"); };
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| ^^^^^^^^^^^^^^^^^^^^
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...
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LL | demo! { impl async Trait }
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| -------------------------- in this macro invocation
9+
|
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= note: this error originates in the macro `demo` (in Nightly builds, run with -Z macro-backtrace for more info)
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error: ty
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--> $DIR/mbe-async-trait-bound-theoretical-regression.rs:8:19
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|
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LL | ($ty:ty) => { compile_error!("ty"); };
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| ^^^^^^^^^^^^^^^^^^^^
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...
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LL | demo! { dyn async Trait }
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| ------------------------- in this macro invocation
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|
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= note: this error originates in the macro `demo` (in Nightly builds, run with -Z macro-backtrace for more info)
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error[E0658]: async closures are unstable
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--> $DIR/mbe-async-trait-bound-theoretical-regression.rs:15:14
25+
|
26+
LL | demo! { impl async Trait }
27+
| ^^^^^
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|
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= note: see issue #62290 <https://github.com/rust-lang/rust/issues/62290> for more information
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= help: add `#![feature(async_closure)]` to the crate attributes to enable
31+
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
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= help: to use an async block, remove the `||`: `async {`
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error[E0658]: async closures are unstable
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--> $DIR/mbe-async-trait-bound-theoretical-regression.rs:18:13
36+
|
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LL | demo! { dyn async Trait }
38+
| ^^^^^
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|
40+
= note: see issue #62290 <https://github.com/rust-lang/rust/issues/62290> for more information
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= help: add `#![feature(async_closure)]` to the crate attributes to enable
42+
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
43+
= help: to use an async block, remove the `||`: `async {`
44+
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error: aborting due to 4 previous errors
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For more information about this error, try `rustc --explain E0658`.

‎tests/ui/async-await/async-fn/trait-bounds-in-macro.rs

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@@ -0,0 +1,12 @@
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//@ edition: 2021
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macro_rules! x {
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($x:item) => {}
5+
}
6+
7+
x! {
8+
async fn foo() -> impl async Fn() { }
9+
//~^ ERROR async closures are unstable
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}
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fn main() {}

‎tests/ui/async-await/async-fn/trait-bounds-in-macro.stderr

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@@ -0,0 +1,14 @@
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error[E0658]: async closures are unstable
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--> $DIR/trait-bounds-in-macro.rs:8:28
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|
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LL | async fn foo() -> impl async Fn() { }
5+
| ^^^^^
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|
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= note: see issue #62290 <https://github.com/rust-lang/rust/issues/62290> for more information
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= help: add `#![feature(async_closure)]` to the crate attributes to enable
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= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
10+
= help: to use an async block, remove the `||`: `async {`
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error: aborting due to 1 previous error
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For more information about this error, try `rustc --explain E0658`.

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