Support RTN on associated methods from supertraits

tests/ui/associated-type-bounds/return-type-notation/missing.rs

@@ -8,6 +8,6 @@ trait Trait {
 }
 
 fn bar<T: Trait<methid(): Send>>() {}
-//~^ ERROR cannot find associated function `methid` in trait `Trait`
+//~^ ERROR cannot find associated function `methid` for `Trait`
 
 fn main() {}

tests/ui/associated-type-bounds/return-type-notation/missing.stderr

@@ -7,7 +7,7 @@ LL | #![feature(return_type_notation, async_fn_in_trait)]
    = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
    = note: `#[warn(incomplete_features)]` on by default
 
-error: cannot find associated function `methid` in trait `Trait`
+error: cannot find associated function `methid` for `Trait`
   --> $DIR/missing.rs:10:17
    |
 LL | fn bar<T: Trait<methid(): Send>>() {}

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

@@ -0,0 +1,25 @@
+// edition:2021
+// check-pass
+
+#![feature(async_fn_in_trait, return_type_notation)]
+//~^ WARN the feature `return_type_notation` is incomplete
+
+trait Super<'a> {
+    async fn test();
+}
+impl Super<'_> for () {
+    async fn test() {}
+}
+
+trait Foo: for<'a> Super<'a> {}
+impl Foo for () {}
+
+fn test<T>()
+where
+    T: Foo<test(): Send>,
+{
+}
+
+fn main() {
+    test::<()>();
+}

tests/ui/async-await/return-type-notation/super-method-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/super-method-bound.rs:4:31
+   |
+LL | #![feature(async_fn_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
+