In suggest_missing_return_type, erase late bound regions after normalizing

src/test/ui/generic-associated-types/issue-88360.rs

@@ -0,0 +1,19 @@
+#![feature(generic_associated_types)]
+
+trait GatTrait {
+    type Gat<'a>;
+
+    fn test(&self) -> Self::Gat<'_>;
+}
+
+trait SuperTrait<T>
+where
+    for<'a> Self: GatTrait<Gat<'a> = &'a T>,
+{
+    fn copy(&self) -> Self::Gat<'_> where T: Copy {
+        *self.test()
+        //~^ mismatched types
+    }
+}
+
+fn main() {}

src/test/ui/generic-associated-types/issue-88360.stderr

@@ -0,0 +1,20 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-88360.rs:14:9
+   |
+LL | trait SuperTrait<T>
+   |                  - this type parameter
+...
+LL |     fn copy(&self) -> Self::Gat<'_> where T: Copy {
+   |                       ------------- expected `&T` because of return type
+LL |         *self.test()
+   |         ^^^^^^^^^^^^
+   |         |
+   |         expected `&T`, found type parameter `T`
+   |         help: consider borrowing here: `&*self.test()`
+   |
+   = note:   expected reference `&T`
+           found type parameter `T`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.