1 files changed, 16 insertions, 0 deletions
diff --git a/tests/ui/traits/assoc-type-in-superbad.rs b/tests/ui/traits/assoc-type-in-superbad.rs
new file mode 100644
index 000000000..65340b2a2
--- /dev/null
+++ b/tests/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 expected `IntoIter<i32>` to be an iterator that yields `u32`, but it yields `i32`
+}
+
+fn main() {}