1 files changed, 29 insertions, 0 deletions

diff --git a/src/test/ui/issues/issue-20763-1.rs b/src/test/ui/issues/issue-20763-1.rs
new file mode 100644
index 000000000..858d313fc
--- /dev/null
+++ b/src/test/ui/issues/issue-20763-1.rs
@@ -0,0 +1,29 @@
+// check-pass
+#![allow(dead_code)]
+// pretty-expanded FIXME #23616
+
+trait T0 {
+    type O;
+    fn dummy(&self) { }
+}
+
+struct S<A>(A);
+impl<A> T0 for S<A> { type O = A; }
+
+trait T1: T0 {
+    // this looks okay but as we see below, `f` is unusable
+    fn m0<F: Fn(<Self as T0>::O) -> bool>(self, f: F) -> bool;
+}
+
+// complains about the bounds on F here not being required by the trait
+impl<A> T1 for S<A> {
+    fn m0<F: Fn(A) -> bool>(self, f: F) -> bool { f(self.0) }
+}
+
+// // complains about mismatched types: <S<A> as T0>::O vs. A
+// impl<A> T1 for S<A>
+// {
+//     fn m0<F: Fn(<Self as T0>::O) -> bool>(self, f: F) -> bool { f(self.0) }
+// }
+
+fn main() { }