template <interface F, interface C> interface AFolder  
{
  ...
};

template <interface F, interface C> interface IFolder : extends AFolder <F, C>    
{
  ... 
};

template <interface F, interface C> mixin WR TFolder 
{
  ...
};

class WR Folder : implements IFolder <IFrameWindow, IClientWindow>, 
                     imports TFolder <IFrameWindow, IClientWindow>  
{
  ...
};