From 02b3664766f1053746a3068c6eed6c464d8a40dc Mon Sep 17 00:00:00 2001 From: Michael Goulet Date: Tue, 21 Feb 2023 17:54:00 +0000 Subject: [PATCH 1/2] Drive-by assertion in collect_return_position_impl_trait_in_trait_tys --- compiler/rustc_hir_analysis/src/check/compare_impl_item.rs | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs index 50005582f7cec..3409b55327244 100644 --- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs +++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs @@ -648,6 +648,13 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>( tcx.fn_sig(trait_m.def_id).subst(tcx, trait_to_placeholder_substs), ) .fold_with(&mut collector); + + debug_assert_ne!( + collector.types.len(), + 0, + "expect >1 RPITITs in call to `collect_return_position_impl_trait_in_trait_tys`" + ); + let trait_sig = ocx.normalize(&norm_cause, param_env, unnormalized_trait_sig); trait_sig.error_reported()?; let trait_return_ty = trait_sig.output(); From 9bf32c40b4c1b7558aee3421ed3e8e73ef518dd9 Mon Sep 17 00:00:00 2001 From: Michael Goulet Date: Tue, 21 Feb 2023 18:27:17 +0000 Subject: [PATCH 2/2] Don't project specializable RPITIT projection --- .../src/traits/project.rs | 27 +++++-- ...ont-project-to-specializable-projection.rs | 71 +++++++++++++++++++ ...project-to-specializable-projection.stderr | 26 +++++++ 3 files changed, 119 insertions(+), 5 deletions(-) create mode 100644 tests/ui/async-await/in-trait/dont-project-to-specializable-projection.rs create mode 100644 tests/ui/async-await/in-trait/dont-project-to-specializable-projection.stderr diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs index 279725b16d8a6..c9e46ba41b057 100644 --- a/compiler/rustc_trait_selection/src/traits/project.rs +++ b/compiler/rustc_trait_selection/src/traits/project.rs @@ -1307,21 +1307,38 @@ fn assemble_candidate_for_impl_trait_in_trait<'cx, 'tcx>( let _ = selcx.infcx.commit_if_ok(|_| { match selcx.select(&obligation.with(tcx, trait_predicate)) { Ok(Some(super::ImplSource::UserDefined(data))) => { - candidate_set.push_candidate(ProjectionCandidate::ImplTraitInTrait(data)); - Ok(()) + let Ok(leaf_def) = specialization_graph::assoc_def(tcx, data.impl_def_id, trait_fn_def_id) else { + return Err(()); + }; + // Only reveal a specializable default if we're past type-checking + // and the obligation is monomorphic, otherwise passes such as + // transmute checking and polymorphic MIR optimizations could + // get a result which isn't correct for all monomorphizations. + if leaf_def.is_final() + || (obligation.param_env.reveal() == Reveal::All + && !selcx + .infcx + .resolve_vars_if_possible(obligation.predicate.trait_ref(tcx)) + .still_further_specializable()) + { + candidate_set.push_candidate(ProjectionCandidate::ImplTraitInTrait(data)); + Ok(()) + } else { + Err(()) + } } Ok(None) => { candidate_set.mark_ambiguous(); - return Err(()); + Err(()) } Ok(Some(_)) => { // Don't know enough about the impl to provide a useful signature - return Err(()); + Err(()) } Err(e) => { debug!(error = ?e, "selection error"); candidate_set.mark_error(e); - return Err(()); + Err(()) } } }); diff --git a/tests/ui/async-await/in-trait/dont-project-to-specializable-projection.rs b/tests/ui/async-await/in-trait/dont-project-to-specializable-projection.rs new file mode 100644 index 0000000000000..afd3db5e0525e --- /dev/null +++ b/tests/ui/async-await/in-trait/dont-project-to-specializable-projection.rs @@ -0,0 +1,71 @@ +// edition: 2021 +// known-bug: #108309 + +#![feature(async_fn_in_trait)] +#![feature(min_specialization)] + +struct MyStruct; + +trait MyTrait { + async fn foo(_: T) -> &'static str; +} + +impl MyTrait for MyStruct { + default async fn foo(_: T) -> &'static str { + "default" + } +} + +impl MyTrait for MyStruct { + async fn foo(_: i32) -> &'static str { + "specialized" + } +} + +async fn async_main() { + assert_eq!(MyStruct::foo(42).await, "specialized"); + assert_eq!(indirection(42).await, "specialized"); +} + +async fn indirection(x: T) -> &'static str { + //explicit type coercion is currently necessary + // because of https://github.com/rust-lang/rust/issues/67918 + >::foo(x).await +} + +// ------------------------------------------------------------------------- // +// Implementation Details Below... + +use std::future::Future; +use std::pin::Pin; +use std::task::*; + +pub fn noop_waker() -> Waker { + let raw = RawWaker::new(std::ptr::null(), &NOOP_WAKER_VTABLE); + + // SAFETY: the contracts for RawWaker and RawWakerVTable are upheld + unsafe { Waker::from_raw(raw) } +} + +const NOOP_WAKER_VTABLE: RawWakerVTable = RawWakerVTable::new(noop_clone, noop, noop, noop); + +unsafe fn noop_clone(_p: *const ()) -> RawWaker { + RawWaker::new(std::ptr::null(), &NOOP_WAKER_VTABLE) +} + +unsafe fn noop(_p: *const ()) {} + +fn main() { + let mut fut = async_main(); + + // Poll loop, just to test the future... + let waker = noop_waker(); + let ctx = &mut Context::from_waker(&waker); + + loop { + match unsafe { Pin::new_unchecked(&mut fut).poll(ctx) } { + Poll::Pending => {} + Poll::Ready(()) => break, + } + } +} diff --git a/tests/ui/async-await/in-trait/dont-project-to-specializable-projection.stderr b/tests/ui/async-await/in-trait/dont-project-to-specializable-projection.stderr new file mode 100644 index 0000000000000..371122ea71ec0 --- /dev/null +++ b/tests/ui/async-await/in-trait/dont-project-to-specializable-projection.stderr @@ -0,0 +1,26 @@ +warning: the feature `async_fn_in_trait` is incomplete and may not be safe to use and/or cause compiler crashes + --> $DIR/dont-project-to-specializable-projection.rs:4:12 + | +LL | #![feature(async_fn_in_trait)] + | ^^^^^^^^^^^^^^^^^ + | + = note: see issue #91611 for more information + = note: `#[warn(incomplete_features)]` on by default + +error[E0053]: method `foo` has an incompatible type for trait + --> $DIR/dont-project-to-specializable-projection.rs:14:35 + | +LL | default async fn foo(_: T) -> &'static str { + | ^^^^^^^^^^^^ expected associated type, found future + | +note: type in trait + --> $DIR/dont-project-to-specializable-projection.rs:10:27 + | +LL | async fn foo(_: T) -> &'static str; + | ^^^^^^^^^^^^ + = note: expected signature `fn(_) -> impl Future` + found signature `fn(_) -> impl Future` + +error: aborting due to previous error; 1 warning emitted + +For more information about this error, try `rustc --explain E0053`.