add test for const eval errors in patterns

src/test/compile-fail/const-pattern-not-const-evaluable.rs

@@ -0,0 +1,39 @@
+// Copyright 2015 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.
+
+#![feature(const_fn)]
+
+enum Cake {
+    BlackForest,
+    Marmor,
+}
+use Cake::*;
+
+const BOO: (Cake, Cake) = (Marmor, BlackForest);
+//~^ ERROR: constant evaluation error: non-constant path in constant expression [E0471]
+const FOO: Cake = BOO.1;
+
+const fn foo() -> Cake {
+    Marmor //~ ERROR: constant evaluation error: non-constant path in constant expression [E0471]
+    //~^ ERROR: non-constant path in constant expression
+}
+
+const WORKS: Cake = Marmor;
+
+const GOO: Cake = foo();
+
+fn main() {
+    match BlackForest {
+        FOO => println!("hi"), //~ NOTE: in pattern here
+        GOO => println!("meh"), //~ NOTE: in pattern here
+        WORKS => println!("möp"),
+        _ => println!("bye"),
+    }
+}