1 files changed, 16 insertions, 0 deletions
diff --git a/src/test/ui/traits/assoc-type-in-superbad.rs b/src/test/ui/traits/assoc-type-in-superbad.rs
new file mode 100644
index 000000000..579ce7cf7
--- /dev/null
+++ b/src/test/ui/traits/assoc-type-in-superbad.rs
@@ -0,0 +1,16 @@
+// Test case where an associated type is referenced from within the
+// supertrait definition, and the impl makes the wrong
+// associations. Issue #20220.
+
+use std::vec::IntoIter;
+
+pub trait Foo: Iterator<Item=<Self as Foo>::Key> {
+    type Key;
+}
+
+impl Foo for IntoIter<i32> {
+    type Key = u32; //~ ERROR type mismatch
+}
+
+fn main() {
+}