title: Is in-class enum forward declaration possible?
body: <p>I know that in C++11 it's possible to forward declare an enum type (if storage type is provided) e.g. </p>
  
  <pre><code>enum E : short;
  void foo(E e);
  
  ....
  
  enum E : short
  {
      VALUE_1,
      VALUE_2,
      ....
  }
  </code></pre>
  
  <p>But I would like to forward declare an enum defined within a class e.g.</p>
  
  <pre><code>enum Foo::E : short;
  void foo(E e);
  
  ....
  
  class Foo
  {
      enum E : short
      {
          VALUE_1,
          VALUE_2,
      ....
      }
  }
  </code></pre>
  
  <p>Is something like this possible in C++11 ?</p>