Disallowed patterns in extern fn declarations.

Closes #10877

src/test/compile-fail/issue-10877.rs

@@ -0,0 +1,24 @@
+// 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 Foo { x: int }
+extern {
+    fn foo(1: ());
+    //~^ ERROR: patterns aren't allowed in foreign function declarations
+    fn bar((): int);
+    //~^ ERROR: patterns aren't allowed in foreign function declarations
+    fn baz(Foo { x }: int);
+    //~^ ERROR: patterns aren't allowed in foreign function declarations
+    fn qux((x,y): ());
+    //~^ ERROR: patterns aren't allowed in foreign function declarations
+    fn this_is_actually_ok(a: uint);
+    fn and_so_is_this(_: uint);
+}
+fn main() {}