1 files changed, 33 insertions, 0 deletions
diff --git a/tests/ui/unboxed-closures/unboxed-closures-fnmut-as-fnonce.rs b/tests/ui/unboxed-closures/unboxed-closures-fnmut-as-fnonce.rs
new file mode 100644
index 000000000..bd577f7c4
--- /dev/null
+++ b/tests/ui/unboxed-closures/unboxed-closures-fnmut-as-fnonce.rs
@@ -0,0 +1,33 @@
+// run-pass
+// Checks that the Fn trait hierarchy rules permit
+// FnMut or FnOnce to be used where FnMut is implemented.
+
+#![feature(unboxed_closures, fn_traits)]
+
+struct S;
+
+impl FnMut<(i32,)> for S {
+    extern "rust-call" fn call_mut(&mut self, (x,): (i32,)) -> i32 {
+        x * x
+    }
+}
+
+impl FnOnce<(i32,)> for S {
+    type Output = i32;
+
+    extern "rust-call" fn call_once(mut self, args: (i32,)) -> i32 { self.call_mut(args) }
+}
+
+fn call_it_mut<F:FnMut(i32)->i32>(f: &mut F, x: i32) -> i32 {
+    f(x)
+}
+
+fn call_it_once<F:FnOnce(i32)->i32>(f: F, x: i32) -> i32 {
+    f(x)
+}
+
+fn main() {
+    let y = call_it_mut(&mut S, 22);
+    let z = call_it_once(S, 22);
+    assert_eq!(y, z);
+}