Rollup merge of #111861 - compiler-errors:rtn-in-super, r=jackh726

Don't ICE on return-type notation when promoting trait preds to associated type bounds

Fixes #111846

Author: matthiaskrgr

compiler/rustc_hir_analysis/src/collect/predicates_of.rs

@@ -427,6 +427,8 @@ pub(super) fn explicit_predicates_of<'tcx>(
             //   supertrait).
             if let ty::Alias(ty::Projection, projection) = ty.kind() {
                 projection.substs == trait_identity_substs
+                    // FIXME(return_type_notation): This check should be more robust
+                    && !tcx.is_impl_trait_in_trait(projection.def_id)
                     && tcx.associated_item(projection.def_id).container_id(tcx)
                         == def_id.to_def_id()
             } else {

tests/ui/async-await/return-type-notation/supertrait-bound.rs

@@ -0,0 +1,11 @@
+// check-pass
+
+#![feature(return_position_impl_trait_in_trait, return_type_notation)]
+//~^ WARN the feature `return_type_notation` is incomplete and may not be safe to use
+
+trait IntFactory {
+    fn stream(&self) -> impl Iterator<Item = i32>;
+}
+trait SendIntFactory: IntFactory<stream(): Send> + Send {}
+
+fn main() {}

tests/ui/async-await/return-type-notation/supertrait-bound.stderr

@@ -0,0 +1,11 @@
+warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/supertrait-bound.rs:3:49
+   |
+LL | #![feature(return_position_impl_trait_in_trait, return_type_notation)]
+   |                                                 ^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+warning: 1 warning emitted
+