Created attachment 26752 [details]
Output of -v option and preprocessed file

Here is a reproducer;

///////////////////////////////////////////////
// An enclosing class template is necessary to
// reproduce the bug.
template<typename T>
struct S
{
  template<typename U>
  struct Unary                        // Line 5
  {};

  template<unsigned, typename... Args>
  struct Dispatch                     // Line 9
    : public Unary<Args...>
  {};

  template<typename... Args>
  struct Variadic
    : public Dispatch<sizeof...(Args), Args...>
  {};
};

int main()
{
  S<void>::Variadic<void> z;
}
///////////////////////////////////////////////

GCC 4.7.0 20120218 (experimental) with -std=c++11 complains about the above code;

main.cpp: In instantiation of 'struct S<void>::Dispatch<1u, void>':
main.cpp:14:10:   required from 'struct S<void>::Variadic<void>'
main.cpp:21:27:   required from here
main.cpp:9:10: error: wrong number of template arguments (2, should be 1)
main.cpp:5:10: error: provided for 'template<class T> template<class U> struct S<T>::Unary'

Obviously, just one template argument is passed to `Unary'. However, GCC misinterprets the number of template arguments as two.