Add test to check that we do not get a cycle due to resolving Self::Bar in the where clauses

Author: nikomatsakis

src/test/ui/associated-type-bounds/super-trait-where-referencing-self.rs

@@ -0,0 +1,27 @@
+// check-pass
+
+// Test that we do not get a cycle due to
+// resolving `Self::Bar` in the where clauses
+// on a trait definition (in particular, in
+// a where clause that is defining a superpredicate).
+
+trait Foo {
+    type Bar;
+}
+trait Qux
+where
+    Self: Foo,
+    Self: AsRef<Self::Bar>,
+{
+}
+trait Foo2 {}
+
+trait Qux2
+where
+    Self: Foo2,
+    Self: AsRef<Self::Bar>,
+{
+    type Bar;
+}
+
+fn main() {}