1 files changed, 56 insertions, 0 deletions
diff --git a/src/test/ui/associated-types/defaults-cyclic-pass-2.rs b/src/test/ui/associated-types/defaults-cyclic-pass-2.rs
new file mode 100644
index 000000000..69315a022
--- /dev/null
+++ b/src/test/ui/associated-types/defaults-cyclic-pass-2.rs
@@ -0,0 +1,56 @@
+// check-pass
+
+#![feature(associated_type_defaults)]
+
+// Having a cycle in assoc. type defaults is okay, as long as there's no impl
+// that retains it.
+trait Tr {
+    type A = Vec<Self::B>;
+    type B = Box<Self::A>;
+
+    fn f();
+}
+
+// An impl has to break the cycle to be accepted.
+impl Tr for u8 {
+    type A = u8;
+
+    fn f() {
+        // Check that the type propagates as expected (seen from inside the impl)
+        let _: Self::A = 0u8;
+        let _: Self::B = Box::new(0u8);
+    }
+}
+
+impl Tr for String {
+    type B = ();
+
+    fn f() {
+        // Check that the type propagates as expected (seen from inside the impl)
+        let _: Self::A = Vec::<()>::new();
+        let _: Self::B = ();
+    }
+}
+
+impl Tr for () {
+    type A = Vec<()>;
+    type B = u8;
+
+    fn f() {
+        // Check that the type propagates as expected (seen from inside the impl)
+        let _: Self::A = Vec::<()>::new();
+        let _: Self::B = 0u8;
+    }
+}
+
+fn main() {
+    // Check that both impls now have the right types (seen from outside the impls)
+    let _: <u8 as Tr>::A = 0u8;
+    let _: <u8 as Tr>::B = Box::new(0u8);
+
+    let _: <String as Tr>::A = Vec::<()>::new();
+    let _: <String as Tr>::B = ();
+
+    let _: <() as Tr>::A = Vec::<()>::new();
+    let _: <() as Tr>::B = 0u8;
+}