Skip to content
Merged
Show file tree
Hide file tree
Changes from all commits
Commits
File filter

Filter by extension

Filter by extension

Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
12 changes: 4 additions & 8 deletions compiler/rustc_hir_typeck/src/closure.rs
Original file line number Diff line number Diff line change
Expand Up @@ -454,28 +454,24 @@ 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)
}
// It's possible we've passed the closure to a (somewhat out-of-fashion)
// `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)
}
Expand Down
14 changes: 14 additions & 0 deletions tests/ui/async-await/async-closures/call-once-deduction.rs
Original file line number Diff line number Diff line change
@@ -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 || {});
}
Loading