Collect relevant item bounds from trait clauses for nested rigid proj…

…ections

compiler/rustc_hir_analysis/src/collect/item_bounds.rs

@@ -35,11 +35,22 @@ fn associated_type_bounds<'tcx>(
  let trait_predicates = tcx.trait_explicit_predicates_and_bounds(trait_def_id);
 
  let bounds_from_parent = trait_predicates.predicates.iter().copied().filter(|(pred, _)| {
- match pred.kind().skip_binder() {
- ty::ClauseKind::Trait(tr) => tr.self_ty() == item_ty,
- ty::ClauseKind::Projection(proj) => proj.projection_ty.self_ty() == item_ty,
- ty::ClauseKind::TypeOutlives(outlives) => outlives.0 == item_ty,
- _ => false,
+ let mut clause_ty = match pred.kind().skip_binder() {
+ ty::ClauseKind::Trait(tr) => tr.self_ty(),
+ ty::ClauseKind::Projection(proj) => proj.projection_ty.self_ty(),
+ ty::ClauseKind::TypeOutlives(outlives) => outlives.0,
+ _ => return false,
+ };
+
+ loop {
+ if clause_ty == item_ty {
+ return true;
+ } else if let ty::Alias(ty::Projection, alias_ty) = *clause_ty.kind() {
+ clause_ty = alias_ty.self_ty();
+ continue;
+ }
+
+ return false;
  }
  });
 

tests/ui/associated-types/imply-relevant-nested-item-bounds-2.rs

@@ -0,0 +1,28 @@
+// check-pass
+// revisions: current next
+//[next] compile-flags: -Znext-solver
+
+trait Trait
+where
+ Self::Assoc: Clone,
+{
+ type Assoc;
+}
+
+fn foo<T: Trait>(x: &T::Assoc) -> T::Assoc {
+ x.clone()
+}
+
+trait Trait2
+where
+ Self::Assoc: Iterator,
+ <Self::Assoc as Iterator>::Item: Clone,
+{
+ type Assoc;
+}
+
+fn foo2<T: Trait2>(x: &<T::Assoc as Iterator>::Item) -> <T::Assoc as Iterator>::Item {
+ x.clone()
+}
+
+fn main() {}

tests/ui/associated-types/imply-relevant-nested-item-bounds.rs

@@ -0,0 +1,23 @@
+// check-pass
+// revisions: current next
+//[next] compile-flags: -Znext-solver
+
+trait Foo
+where
+ Self::Iterator: Iterator,
+ <Self::Iterator as Iterator>::Item: Bar,
+{
+ type Iterator;
+
+ fn iter() -> Self::Iterator;
+}
+
+trait Bar {
+ fn bar(&self);
+}
+
+fn x<T: Foo>() {
+ T::iter().next().unwrap().bar();
+}
+
+fn main() {}