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Allow desugaring async fn in trait to compatible, concrete future types

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This commit is contained in:
Michael Goulet 2024-01-18 16:39:20 +00:00
parent ea37e8091f
commit 16cbdd0321
9 changed files with 15 additions and 77 deletions
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4
compiler/rustc_hir_analysis/messages.ftl
View File

@ -33,10 +33,6 @@ hir_analysis_associated_type_trait_uninferred_generic_params = cannot use the as
hir_analysis_associated_type_trait_uninferred_generic_params_multipart_suggestion = use a fully qualified path with explicit lifetimes
hir_analysis_async_trait_impl_should_be_async =
method `{$method_name}` should be async because the method from the trait is async
.trait_item_label = required because the trait method is async
hir_analysis_auto_deref_reached_recursion_limit = reached the recursion limit while auto-dereferencing `{$ty}`
.label = deref recursion limit reached
.help = consider increasing the recursion limit by adding a `#![recursion_limit = "{$suggested_limit}"]` attribute to your crate (`{$crate_name}`)

31
compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
View File

@ -74,7 +74,6 @@ fn check_method_is_structurally_compatible<'tcx>(
compare_generic_param_kinds(tcx, impl_m, trait_m, delay)?;
compare_number_of_method_arguments(tcx, impl_m, trait_m, delay)?;
compare_synthetic_generics(tcx, impl_m, trait_m, delay)?;
compare_asyncness(tcx, impl_m, trait_m, delay)?;
check_region_bounds_on_impl_item(tcx, impl_m, trait_m, delay)?;
Ok(())
}
@ -414,36 +413,6 @@ fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
}
}
fn compare_asyncness<'tcx>(
tcx: TyCtxt<'tcx>,
impl_m: ty::AssocItem,
trait_m: ty::AssocItem,
delay: bool,
) -> Result<(), ErrorGuaranteed> {
if tcx.asyncness(trait_m.def_id).is_async() {
match tcx.fn_sig(impl_m.def_id).skip_binder().skip_binder().output().kind() {
ty::Alias(ty::Opaque, ..) => {
// allow both `async fn foo()` and `fn foo() -> impl Future`
}
ty::Error(_) => {
// We don't know if it's ok, but at least it's already an error.
}
_ => {
return Err(tcx
.dcx()
.create_err(crate::errors::AsyncTraitImplShouldBeAsync {
span: tcx.def_span(impl_m.def_id),
method_name: trait_m.name,
trait_item_span: tcx.hir().span_if_local(trait_m.def_id),
})
.emit_unless(delay));
}
};
}
Ok(())
}
/// Given a method def-id in an impl, compare the method signature of the impl
/// against the trait that it's implementing. In doing so, infer the hidden types
/// that this method's signature provides to satisfy each return-position `impl Trait`

11
compiler/rustc_hir_analysis/src/errors.rs
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@ -166,17 +166,6 @@ pub struct LifetimesOrBoundsMismatchOnTrait {
pub ident: Ident,
}
#[derive(Diagnostic)]
#[diag(hir_analysis_async_trait_impl_should_be_async)]
pub struct AsyncTraitImplShouldBeAsync {
#[primary_span]
// #[label]
pub span: Span,
#[label(hir_analysis_trait_item_label)]
pub trait_item_span: Option<Span>,
pub method_name: Symbol,
}
#[derive(Diagnostic)]
#[diag(hir_analysis_drop_impl_on_wrong_item, code = E0120)]
pub struct DropImplOnWrongItem {

2
tests/ui/async-await/in-trait/async-example-desugared-boxed.rs
View File

@ -1,4 +1,5 @@
// edition: 2021
// check-pass
use std::future::Future;
use std::pin::Pin;
@ -9,7 +10,6 @@ trait MyTrait {
impl MyTrait for i32 {
fn foo(&self) -> Pin<Box<dyn Future<Output = i32> + '_>> {
//~^ ERROR method `foo` should be async
Box::pin(async { *self })
}
}

11
tests/ui/async-await/in-trait/async-example-desugared-boxed.stderr
View File

@ -1,11 +0,0 @@
error: method `foo` should be async because the method from the trait is async
--> $DIR/async-example-desugared-boxed.rs:11:5
|
LL | async fn foo(&self) -> i32;
| --------------------------- required because the trait method is async
...
LL | fn foo(&self) -> Pin<Box<dyn Future<Output = i32> + '_>> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to 1 previous error

2
tests/ui/async-await/in-trait/async-example-desugared-manual.rs
View File

@ -1,4 +1,5 @@
// edition: 2021
// check-pass
use std::future::Future;
use std::task::Poll;
@ -17,7 +18,6 @@ fn poll(self: std::pin::Pin<&mut Self>, _: &mut std::task::Context<'_>) -> Poll<
impl MyTrait for u32 {
fn foo(&self) -> MyFuture {
//~^ ERROR method `foo` should be async
MyFuture
}
}

11
tests/ui/async-await/in-trait/async-example-desugared-manual.stderr
View File

@ -1,11 +0,0 @@
error: method `foo` should be async because the method from the trait is async
--> $DIR/async-example-desugared-manual.rs:19:5
|
LL | async fn foo(&self) -> i32;
| --------------------------- required because the trait method is async
...
LL | fn foo(&self) -> MyFuture {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to 1 previous error

2
tests/ui/async-await/in-trait/fn-not-async-err.rs
View File

@ -8,7 +8,7 @@ trait MyTrait {
impl MyTrait for i32 {
fn foo(&self) -> i32 {
//~^ ERROR: method `foo` should be async
//~^ ERROR: `i32` is not a future
*self
}
}

18
tests/ui/async-await/in-trait/fn-not-async-err.stderr
View File

@ -1,11 +1,17 @@
error: method `foo` should be async because the method from the trait is async
--> $DIR/fn-not-async-err.rs:10:5
error[E0277]: `i32` is not a future
--> $DIR/fn-not-async-err.rs:10:22
|
LL | fn foo(&self) -> i32 {
| ^^^ `i32` is not a future
|
= help: the trait `Future` is not implemented for `i32`
= note: i32 must be a future or must implement `IntoFuture` to be awaited
note: required by a bound in `MyTrait::{opaque#0}`
--> $DIR/fn-not-async-err.rs:6:5
|
LL | async fn foo(&self) -> i32;
| --------------------------- required because the trait method is async
...
LL | fn foo(&self) -> i32 {
| ^^^^^^^^^^^^^^^^^^^^
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `MyTrait::{opaque#0}`
error: aborting due to 1 previous error
For more information about this error, try `rustc --explain E0277`.