don't treat unit patterns as wildcard patterns

Fixes rust-lang#32004

Author: arielb1

Diff for: src/librustc_typeck/check/_match.rs

@@ -204,7 +204,7 @@ pub fn check_pat<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
             check_pat_enum(pcx, pat, path, subpats.as_ref().map(|v| &v[..]), expected, true);
         }
         PatKind::Path(ref path) => {
-            check_pat_enum(pcx, pat, path, None, expected, false);
+            check_pat_enum(pcx, pat, path, Some(&[]), expected, false);
         }
         PatKind::QPath(ref qself, ref path) => {
             let self_ty = fcx.to_ty(&qself.ty);

Diff for: src/test/compile-fail/issue-32004.rs

@@ -0,0 +1,29 @@
+// Copyright 2016 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.
+
+enum Foo {
+    Bar(i32),
+    Baz
+}
+
+struct S;
+
+fn main() {
+    match Foo::Baz {
+        Foo::Bar => {}
+        //~^ ERROR this pattern has 0 fields, but the corresponding variant
+        _ => {}
+    }
+
+    match S {
+        S(()) => {}
+        //~^ ERROR this pattern has 1 field, but the corresponding struct
+    }
+}