Test implicit this on fields.

dart/tests/language/src/ImplicitThisTest.dart

+// Copyright (c) 2011, 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.
+
+interface Interface {
+  final x;
+}
+
+class Abstract implements Interface {

[kasperl, 2011/11/02 09:03:00]

Maybe add a comment here. Something like: If you say you implement an interface
but you really don't, it means that you're an abstract class that cannot be
instantiated.

+  String toString() => x.toString();
+}
+
+class Concrete extends Abstract {
+  get x() => 7;
+}
+
+class SubConcrete extends Abstract {

[kasperl, 2011/11/02 09:03:00]

How about ConcreteA and ConcreteB? They are not related.

[ahe, 2011/11/02 19:03:57]

But they are, I just subclassed the wrong class. Good catch :-)

+  final x;
+  SubConcrete(this.x);
+}
+
+void main() {
+  var x = new Abstract(); /// 01: static type error
+  Expect.equals(x, x);
+  Expect.equals(new Concrete().toString(), '7');

[kasperl, 2011/11/02 09:03:00]

expected, actual

+  Expect.equals(new SubConcrete(42).toString(), '42');
+  Expect.equals(new SubConcrete(new Concrete()).toString(), '7');
+}