Report compile-time errors for conflicting overrides as specified by latest

tests/language/setter_override_test.dart

+// Copyright (c) 2013, 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 that we do not report a compile-time error when a static setter named
+// foo= is declared in a class inheriting an instance method or getter named
+// foo, and that we do report an error if an instance setter named foo= or
+// instance field name foo is inherited.
+
+import "package:expect/expect.dart";
+
+class A {
+  var foo = 42;  /// 00: compile-time error
+  get foo => 42;  /// 01: static type warning
+  foo() => 42;  /// 02: static type warning
+  set foo(value) { }  /// 03: compile-time error
+}
+
+class B extends A {
+  static var foo_;
+  static set foo(value) { foo_ = value; }
+}
+
+main() {
+  B.foo = 42;
+  Expect.equals(42, B.foo_);
+}