Add test for issue #12552

Closes #12552

src/test/compile-fail/issue-12552.rs

@@ -0,0 +1,21 @@
+// Copyright 2014 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.
+
+// this code used to cause an ICE
+
+fn main() {
+  let t = Err(0);
+  match t {
+    Some(k) => match k { //~ ERROR mismatched types
+      a => println!("{}", a)
+    },
+    None => () //~ ERROR mismatched types
+  }
+}