Specify the types for Element.classes, Element.elements and Node.nodes

tests/language/src/GettersSetters2Test.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.
+
+// Tests classes with getters and setters that do not have the same type.
+
+class A {
+  int a() { return 37;}
+}
+
+class B extends A{
+  int b() { return 38; }
+}
+
+class C {}
+
+class T1 {
+  A getterField; 
+  A get field() { return getterField; }
+  // OK, B is assignable to A
+  void set field(B arg) { getterField = arg; }
+}
+
+class T2 {
+  A getterField; 
+  C setterField; 
+  A get field() { return getterField; }
+
+  // Type C is not assignable to A
+  void set field(C arg) { setterField = arg; } /// 01: static type error
+}
+
+class T3 {
+  B getterField; 
+  B get field() { return getterField; }
+  // OK, A is assignable to B
+  void set field(A arg) { getterField = arg; }
+}
+
+
+main() {
+  T1 instance1 = new T1();
+  T2 instance2 = new T2(); /// 01: continued
+  T3 instance3 = new T3();
+
+  instance1.field = new B();
+  A resultA = instance1.field;
+  instance1.field = new A(); /// 03: dynamic type error
+  B resultB = instance1.field;
+
+  int result;
+  result = instance1.field.a(); 
+  Expect.equals(37, result);
+
+  // Type 'A' has no method named 'b'
+  instance1.field.b(); /// 02: static type error
+
+  instance3.field = new B();
+  result = instance3.field.a();
+  Expect.equals(37, result);
+  result = instance3.field.b();
+  Expect.equals(38, result);
+}