bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

Auto merge of #111161 - compiler-errors:rtn-super, r=cjgillot

Browse source 
Support return-type bounds on associated methods from supertraits

Support `T: Trait<method(): Bound>` when `method` comes from a supertrait, aligning it with the behavior of associated type bounds (both equality and trait bounds).

The only wrinkle is that I have to extend `super_predicates_that_define_assoc_type` to look for *all* items, not just `AssocKind::Ty`. This will also be needed to support `feature(associated_const_equality)` as well, which is subtly broken when it comes to supertraits, though this PR does not fix those yet. There's a slight chance there's a perf regression here, in which case I guess I could split it out into a separate query.
This commit is contained in:
bors 2023-05-07 11:18:22 +00:00
commit 0dddad0dc5
17 changed files with 210 additions and 50 deletions
Download patch file Download diff file Expand all files Collapse all files

8
compiler/rustc_infer/src/traits/util.rs
View file

@ -380,11 +380,11 @@ pub fn transitive_bounds<'tcx>(
}
/// A specialized variant of `elaborate` that only elaborates trait references that may
/// define the given associated type `assoc_name`. It uses the
/// `super_predicates_that_define_assoc_type` query to avoid enumerating super-predicates that
/// define the given associated item with the name `assoc_name`. It uses the
/// `super_predicates_that_define_assoc_item` query to avoid enumerating super-predicates that
/// aren't related to `assoc_item`. This is used when resolving types like `Self::Item` or
/// `T::Item` and helps to avoid cycle errors (see e.g. #35237).
pub fn transitive_bounds_that_define_assoc_type<'tcx>(
pub fn transitive_bounds_that_define_assoc_item<'tcx>(
tcx: TyCtxt<'tcx>,
bounds: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
assoc_name: Ident,
@ -397,7 +397,7 @@ pub fn transitive_bounds_that_define_assoc_type<'tcx>(
let anon_trait_ref = tcx.anonymize_bound_vars(trait_ref);
if visited.insert(anon_trait_ref) {
let super_predicates =
tcx.super_predicates_that_define_assoc_type((trait_ref.def_id(), assoc_name));
tcx.super_predicates_that_define_assoc_item((trait_ref.def_id(), assoc_name));
for (super_predicate, _) in super_predicates.predicates {
let subst_predicate = super_predicate.subst_supertrait(tcx, &trait_ref);
if let Some(binder) = subst_predicate.to_opt_poly_trait_pred() {