Issue 3528. Additional checks for 'case expressions'

tests/language/switch_this_test.dart

-// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-// Test comparison of this and a constant.
-
-class Foo {
-  static final C1 = const Foo('C1');
-  static final C2 = const Foo('C2');
-  static final C3 = const Foo('C3');
-
-  final name;
-  const Foo(this.name);
-
-  foo() {
-    switch (this) {
-      case C1: return C1;
-      case C2: return C2;
-      default: return null;
-    }
-  }
-}
-
-main() {
-  Expect.equals(Foo.C1, Foo.C1.foo());
-  Expect.equals(Foo.C2, Foo.C2.foo());
-  Expect.equals(null, Foo.C3.foo());
-}