bjoernager/rust
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deal with opaque types without cycling

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lcnr 2022-01-19 17:35:26 +01:00 • committed by Oleksandr Babak
parent 3adedc93a9
commit b5b3f33940
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7 changed files with 95 additions and 230 deletions
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34
compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
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@ -532,22 +532,27 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
}
}
ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
bug!(
"asked to assemble auto trait candidates of unexpected type: {:?}",
self_ty
);
}
// Only consider auto impls if there are no manual impls for the root of `self_ty`.
//
// For example, we only consider auto candidates for `&i32: Auto` if no explicit impl
// for `&SomeType: Auto` exists. Due to E0321 the only crate where impls
// for `&SomeType: Auto` can be defined is the crate where `Auto` has been defined.
//
// Generally, we have to guarantee that for all `SimplifiedType`s the only crate
// which may define impls for that type is either the crate defining the type
// or the trait. This should be guaranteed by the orphan check.
ty::Alias(_, _)
if candidates.vec.iter().any(|c| matches!(c, ProjectionCandidate(..))) =>
{
// We do not generate an auto impl candidate for `impl Trait`s which already
// reference our auto trait.
//
// For example during candidate assembly for `impl Send: Send`, we don't have
// to look at the constituent types for this opaque types to figure out that this
// trivially holds.
//
// Note that this is only sound as projection candidates of opaque types
// are always applicable for auto traits.
}
ty::Bool
| ty::Char
| ty::Int(_)
@ -568,6 +573,15 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
| ty::Alias(_, _)
| ty::GeneratorWitness(_)
| ty::GeneratorWitnessMIR(..) => {
// Only consider auto impls if there are no manual impls for the root of `self_ty`.
//
// For example, we only consider auto candidates for `&i32: Auto` if no explicit impl
// for `&SomeType: Auto` exists. Due to E0321 the only crate where impls
// for `&SomeType: Auto` can be defined is the crate where `Auto` has been defined.
//
// Generally, we have to guarantee that for all `SimplifiedType`s the only crate
// which may define impls for that type is either the crate defining the type
// or the trait. This should be guaranteed by the orphan check.
let mut has_impl = false;
self.tcx().for_each_relevant_impl(def_id, self_ty, |_| has_impl = true);
if !has_impl {