Add compile-fail test for #42060

Closes #42060

src/test/compile-fail/issue-42060.rs

@@ -0,0 +1,22 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn main() {
+    let thing = ();
+    let other: typeof(thing) = thing; //~ ERROR attempt to use a non-constant value in a constant
+    //~^ ERROR `typeof` is a reserved keyword but unimplemented [E0516]
+}
+
+fn f(){
+    let q = 1;
+    <typeof(q)>::N //~ ERROR attempt to use a non-constant value in a constant
+    //~^ ERROR `typeof` is a reserved keyword but unimplemented [E0516]
+}
+