diff options
4 files changed, 128 insertions, 6 deletions
diff --git a/compiler/rustc_hir_typeck/src/upvar.rs b/compiler/rustc_hir_typeck/src/upvar.rs index 37f3786c00a..fc98a603dd8 100644 --- a/compiler/rustc_hir_typeck/src/upvar.rs +++ b/compiler/rustc_hir_typeck/src/upvar.rs @@ -1862,8 +1862,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { /// /// (1.) Are we borrowing data owned by the parent closure? We can determine if /// that is the case by checking if the parent capture is by move, EXCEPT if we -/// apply a deref projection, which means we're reborrowing a reference that we -/// captured by move. +/// apply a deref projection of an immutable reference, reborrows of immutable +/// references which aren't restricted to the LUB of the lifetimes of the deref +/// chain. This is why `&'short mut &'long T` can be reborrowed as `&'long T`. /// /// ```rust /// let x = &1i32; // Let's call this lifetime `'1`. @@ -1902,10 +1903,22 @@ fn should_reborrow_from_env_of_parent_coroutine_closure<'tcx>( ) -> bool { // (1.) (!parent_capture.is_by_ref() - && !matches!( - child_capture.place.projections.get(parent_capture.place.projections.len()), - Some(Projection { kind: ProjectionKind::Deref, .. }) - )) + // This is just inlined `place.deref_tys()` but truncated to just + // the child projections. Namely, look for a `&T` deref, since we + // can always extend `&'short mut &'long T` to `&'long T`. + && !child_capture + .place + .projections + .iter() + .enumerate() + .skip(parent_capture.place.projections.len()) + .any(|(idx, proj)| { + matches!(proj.kind, ProjectionKind::Deref) + && matches!( + child_capture.place.ty_before_projection(idx).kind(), + ty::Ref(.., ty::Mutability::Not) + ) + })) // (2.) || matches!(child_capture.info.capture_kind, UpvarCapture::ByRef(ty::BorrowKind::Mutable)) } diff --git a/tests/ui/async-await/async-closures/imm-deref-lending.rs b/tests/ui/async-await/async-closures/imm-deref-lending.rs new file mode 100644 index 00000000000..59f8d434d9c --- /dev/null +++ b/tests/ui/async-await/async-closures/imm-deref-lending.rs @@ -0,0 +1,46 @@ +//@ edition: 2021 +//@ check-pass + +#![feature(impl_trait_in_bindings)] + +struct FooS { + precise: i32, +} + +fn ref_inside_mut(f: &mut &FooS) { + let x: impl AsyncFn() = async move || { + let y = &f.precise; + }; +} + +fn mut_inside_ref(f: &&mut FooS) { + let x: impl AsyncFn() = async move || { + let y = &f.precise; + }; +} + +fn mut_ref_inside_mut(f: &mut &mut FooS) { + let x: impl AsyncFn() = async move || { + let y = &f.precise; + }; +} + +fn ref_inside_box(f: Box<&FooS>) { + let x: impl AsyncFn() = async move || { + let y = &f.precise; + }; +} + +fn box_inside_ref(f: &Box<FooS>) { + let x: impl AsyncFn() = async move || { + let y = &f.precise; + }; +} + +fn box_inside_box(f: Box<Box<FooS>>) { + let x: impl AsyncFn() = async move || { + let y = &f.precise; + }; +} + +fn main() {} diff --git a/tests/ui/async-await/async-closures/imm-deref-not-lending.rs b/tests/ui/async-await/async-closures/imm-deref-not-lending.rs new file mode 100644 index 00000000000..bd1197cc636 --- /dev/null +++ b/tests/ui/async-await/async-closures/imm-deref-not-lending.rs @@ -0,0 +1,49 @@ +//@ edition: 2021 + +#![feature(impl_trait_in_bindings)] + +struct FooS { + precise: i32, +} + +fn ref_inside_mut(f: &mut &FooS) { + let x: impl Fn() -> _ = async move || { + let y = &f.precise; + }; +} + +fn mut_inside_ref(f: &&mut FooS) { + let x: impl Fn() -> _ = async move || { + let y = &f.precise; + }; +} + +// Expected to fail, no immutable reference here. +fn mut_ref_inside_mut(f: &mut &mut FooS) { + let x: impl Fn() -> _ = async move || { + //~^ ERROR async closure does not implement `Fn` + let y = &f.precise; + }; +} + +fn ref_inside_box(f: Box<&FooS>) { + let x: impl Fn() -> _ = async move || { + let y = &f.precise; + }; +} + +fn box_inside_ref(f: &Box<FooS>) { + let x: impl Fn() -> _ = async move || { + let y = &f.precise; + }; +} + +// Expected to fail, no immutable reference here. +fn box_inside_box(f: Box<Box<FooS>>) { + let x: impl Fn() -> _ = async move || { + //~^ ERROR async closure does not implement `Fn` + let y = &f.precise; + }; +} + +fn main() {} diff --git a/tests/ui/async-await/async-closures/imm-deref-not-lending.stderr b/tests/ui/async-await/async-closures/imm-deref-not-lending.stderr new file mode 100644 index 00000000000..cd3ff55e458 --- /dev/null +++ b/tests/ui/async-await/async-closures/imm-deref-not-lending.stderr @@ -0,0 +1,14 @@ +error: async closure does not implement `Fn` because it captures state from its environment + --> $DIR/imm-deref-not-lending.rs:23:29 + | +LL | let x: impl Fn() -> _ = async move || { + | ^^^^^^^^^^^^^ + +error: async closure does not implement `Fn` because it captures state from its environment + --> $DIR/imm-deref-not-lending.rs:43:29 + | +LL | let x: impl Fn() -> _ = async move || { + | ^^^^^^^^^^^^^ + +error: aborting due to 2 previous errors + |