title: GWT 2.4.0 RequestFactory polymorphism
body: <p>Does GWT 2.4 support this case:</p>
  
  <pre><code>@Entity class MyBase {...}
  @Entity class MyChild1 extends MyBase {...}
  @Entity class MyChild2 extends MyBase {...}
  ...
  @ProxyFor(MyBase.class) class MyBaseProxy extends EntityProxy {...}
  @ProxyFor(MyChild1.class) class MyChild1Proxy extends MyBaseProxy {...}
  @ProxyFor(MyChild2.class) class MyChild2Proxy extends MyBaseProxy {...}
  ...
  @Service(ArticleBase.class)
  public interface MyBaseRequest extends RequestContext {
      Request&lt;MyBaseProxy&gt; getStuff(); // MyChild1 here
  }
  ...
  Request&lt;MyBaseProxy&gt; getStuffRequest = request.getStuff();
  getStuffRequest.fire(new Receiver&lt;MyBaseProxy&gt;() {
      @Override
      public void onSuccess(MyBaseProxy proxy) {
          button.setText(((MyChild1Proxy)proxy).getQwerty()); // HERE!
      }
  });
  </code></pre>
  
  <p>?</p>
  
  <p>The problem is, I can't make it work. It's either not supported yet or I need to add some magic annotation somewhere. Everything works fine when I use concrete types, but it doesn't work if I use the base ones.</p>
  
  <p>What do you think?</p>