Uplift some feeding out of associated_type_for_impl_trait_in_impl and into queries

tests/ui/impl-trait/in-trait/rpitit-cycle-in-generics-of.rs

@@ -0,0 +1,18 @@
+//@ check-pass
+
+// Check that we don't hit a query cycle when:
+// 1. Computing generics_of, which requires...
+// 2. Calling resolve_bound_vars, which requires...
+// 3. Calling associated_items, which requires...
+// 4. Calling associated_type_for_impl_trait_in_trait, which requires...
+// 5. Computing generics_of, which cycles.
+
+pub trait Foo<'a> {
+    type Assoc;
+
+    fn demo<T>(other: T) -> impl Foo<'a, Assoc = Self::Assoc>
+    where
+        T: Foo<'a, Assoc = ()>;
+}
+
+fn main() {}