1 files changed, 29 insertions, 0 deletions
diff --git a/src/test/ui/unboxed-closures/unboxed-closures-fnmut-as-fn.rs b/src/test/ui/unboxed-closures/unboxed-closures-fnmut-as-fn.rs
new file mode 100644
index 000000000..867e5fb1d
--- /dev/null
+++ b/src/test/ui/unboxed-closures/unboxed-closures-fnmut-as-fn.rs
@@ -0,0 +1,29 @@
+// Checks that the Fn trait hierarchy rules do not permit
+// Fn to be used where FnMut is implemented.
+
+#![feature(fn_traits, unboxed_closures)]
+
+use std::ops::{Fn,FnMut,FnOnce};
+
+struct S;
+
+impl FnMut<(isize,)> for S {
+    extern "rust-call" fn call_mut(&mut self, (x,): (isize,)) -> isize {
+        x * x
+    }
+}
+
+impl FnOnce<(isize,)> for S {
+    type Output = isize;
+
+    extern "rust-call" fn call_once(mut self, args: (isize,)) -> isize { self.call_mut(args) }
+}
+
+fn call_it<F:Fn(isize)->isize>(f: &F, x: isize) -> isize {
+    f.call((x,))
+}
+
+fn main() {
+    let x = call_it(&S, 22);
+    //~^ ERROR E0277
+}