typename2.c

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

// Build don't link:
// Special g++ Options:

// Copyright (C) 1999 Free Software Foundation

// by Alexandre Oliva <[e-mail]>
// based on bug report by Nick Rasmussen <[e-mail]>

// This is slightly different from typename1.C.  This one tests
// whether the implicit typename extension works.  gcc 2.95 reports:

// warning: lookup of `foo' finds `struct foo'
// warning:   instead of `baz<T>::foo' from dependent base class
// warning:   (use `typename baz::foo' if that's what you meant)

// But baz<T>::foo is not a base class, and `foo' should have been
// found in baz's scope.

struct foo;

template <class T> struct bar {
  typedef int foo;
};

template <class T> struct baz {
  typedef bar<T>::foo foo; // ERROR - implicit typename
  void m(foo); 
};