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Rollup merge of #134017 - compiler-errors:call-once-deduction, r=jieyouxu

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Don't use `AsyncFnOnce::CallOnceFuture` bounds for signature deduction

We shouldn't be using `AsyncFnOnce::CallOnceFuture` projection bounds to deduce anything about the return type of an async closure, **only** `AsyncFnOnce::Output`. This was accidental b/c all we were looking at was the def id of the trait, rather than the projection. This PR fixes that.

This doesn't affect stable code, since `CallOnceFuture` bounds cannot be written on stable.

Fixes #134015
This commit is contained in:
León Orell Valerian Liehr 2024-12-10 13:51:10 +01:00 committed by GitHub
commit 193a95d30b
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GPG Key ID: B5690EEEBB952194
2 changed files with 18 additions and 8 deletions
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12
compiler/rustc_hir_typeck/src/closure.rs
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@ -454,20 +454,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
closure_kind: hir::ClosureKind,
projection: ty::PolyProjectionPredicate<'tcx>,
) -> Option<ExpectedSig<'tcx>> {
let tcx = self.tcx;
let trait_def_id = projection.trait_def_id(tcx);
let def_id = projection.projection_def_id();
// For now, we only do signature deduction based off of the `Fn` and `AsyncFn` traits,
// for closures and async closures, respectively.
match closure_kind {
hir::ClosureKind::Closure
if self.tcx.fn_trait_kind_from_def_id(trait_def_id).is_some() =>
{
hir::ClosureKind::Closure if self.tcx.is_lang_item(def_id, LangItem::FnOnceOutput) => {
self.extract_sig_from_projection(cause_span, projection)
}
hir::ClosureKind::CoroutineClosure(hir::CoroutineDesugaring::Async)
if self.tcx.async_fn_trait_kind_from_def_id(trait_def_id).is_some() =>
if self.tcx.is_lang_item(def_id, LangItem::AsyncFnOnceOutput) =>
{
self.extract_sig_from_projection(cause_span, projection)
}
@ -475,7 +471,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// `F: FnOnce() -> Fut, Fut: Future<Output = T>` style bound. Let's still
// guide inference here, since it's beneficial for the user.
hir::ClosureKind::CoroutineClosure(hir::CoroutineDesugaring::Async)
if self.tcx.fn_trait_kind_from_def_id(trait_def_id).is_some() =>
if self.tcx.is_lang_item(def_id, LangItem::FnOnceOutput) =>
{
self.extract_sig_from_projection_and_future_bound(cause_span, projection)
}

14
tests/ui/async-await/async-closures/call-once-deduction.rs Normal file
View File

@ -0,0 +1,14 @@
//@ edition: 2021
//@ check-pass
#![feature(async_closure, async_fn_traits, unboxed_closures)]
fn bar<F, O>(_: F)
where
F: AsyncFnOnce<(), CallOnceFuture = O>,
{
}
fn main() {
bar(async move || {});
}