auto merge of #15388 : jakub-/rust/issue-12285, r=pcwalton

Unit-like struct patterns are irrefutable, no need for a branch.

And some cleanup while I'm at it.

src/test/run-pass/issue-12285.rs

@@ -0,0 +1,22 @@
+// 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.
+
+struct S;
+
+fn main() {
+    match Some(&S) {
+        Some(&S) => {},
+        _x => unreachable!()
+    }
+    match Some(&S) {
+        Some(&S) => {},
+        None => unreachable!()
+    }
+}