Overriding fields is now permissable.

tests/language/src/FieldOverrideTest.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.
-
+// VMOptions=--enable_type_checks
 // Test overriding of fields.
 
-interface A {}
-interface B1 extends A {}
-interface B2 extends A {}
+
+class A {}
+class B1 extends A {}
+class B2 extends A {}
 
 class Super {
   Super() : super();
 
   B1 field;
 }
 
 class Sub extends Super {
   Sub() : super();
 
-  A field;  /// 01: compile-time error
+  A field;
 }
 
 class SubSub extends Super {
   SubSub() : super();
 
-  B2 field;  /// 02: compile-time error
+  // B2 not assignable to B1
+  B2 field;  /// 01: static type error

[zundel, 2011/12/07 19:44:56]

??? Dartc's type checker flags this as: 


tests/language/src/FieldOverrideTest.dart/FieldOverrideTest.dart:28: cannot
override field of Super because B2 is not assignable to B1


Makes sense to me, but I don't see it in the spec either.

[ahe, 2011/12/08 08:53:46]

Would you mind filing a specification bug?

 }
 
 main() {
-  new SubSub();
+  SubSub val1 = new SubSub();
+  val1.field = new B2();
+  Expect.equals(true, val1.field is B2);
+
+  Sub val2 = new Sub();
+  val2.field = new A();
+  Expect.equals(true, val2.field is A);
+  Expect.equals(false, val2.field is B1);
+  Expect.equals(false, val2.field is B2);
+
+  Super val3 = new Super();
+  val3.field = new B1();
+  Expect.equals(true, val3.field is B1);
+  Expect.equals(false, val3.field is B2);
 }