How to forward declare nested managed class in C++/clr

[lstivers]

OK, for the life of me, I can't find this answer. How can I forward declare a nested managed class? Here is an example of what I'm trying to accomplish:

namespace Geometry
{
   ref class Vectors;
   ref class Points;
   // ref class Points::Point2;   <-- won't compile but this is the idea...

   public ref class Vectors
   {
   public:
      ref class Vector2
      {
      };

      void SomeFunc( Points::Point2 ^ );   //   <===== C2027
   };

   public ref class Points
   {
   public:
      ref class Point2
      {
      };

      void SomeFunc( Vectors::Vector2 ^ );
   };
}