this is a gcc file, you can download it and learn its usetility, for further detail please look at t

				// { dg-do compile }				// Origin: Wolfgang Bangerth 								// PR c++/7347				// Access control for typename during instantiation								template  class Base {				  protected:				    typedef int T;				};								template  class D : public Base {				  public:				    typedef typename Base::T T1;				    D (T1 t);				};								D d(1);