Add regression test

tests/ui/ice-2636.rs

@@ -0,0 +1,32 @@
+// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution.
+//
+// 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.
+
+#![allow(dead_code)]
+
+enum Foo {
+    A,
+    B,
+    C,
+}
+
+macro_rules! test_hash {
+    ($foo:expr, $($t:ident => $ord:expr),+ ) => {
+        use self::Foo::*;
+        match $foo {
+            $ ( & $t => $ord,
+            )*
+        };
+    };
+}
+
+fn main() {
+    let a = Foo::A;
+    test_hash!(&a, A => 0, B => 1, C => 2);
+}
+

tests/ui/ice-2636.stderr

@@ -0,0 +1,16 @@
+error: you don't need to add `&` to both the expression and the patterns
+  --> $DIR/ice-2636.rs:21:9
+   |
+21 | /         match $foo {
+22 | |             $ ( & $t => $ord,
+23 | |             )*
+24 | |         };
+   | |_________^
+...
+30 |       test_hash!(&a, A => 0, B => 1, C => 2);
+   |       --------------------------------------- in this macro invocation
+   |
+   = note: `-D clippy::match-ref-pats` implied by `-D warnings`
+
+error: aborting due to previous error
+