Parse field initializer expressions in the correct scope class

tests/language/regress_18713_test.dart

+// Copyright (c) 2016, 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.
+
+import "package:expect/expect.dart";
+
+class T<X> {
+  final Type tType = X;
+  Type get getTType => X;
+}
+
+class S<Y> {
+  final Type sType = Y;
+  Type get getSType => Y;
+}
+
+class TS<A, B> = T<A> with S<B>;
+
+main() {
+  var ts = new TS<int, String>();
+  Expect.equals("String", ts.sType.toString());
+  Expect.equals("int", ts.tType.toString());
+  Expect.equals("String", ts.getSType.toString());
+  Expect.equals("int", ts.getTType.toString());
+}