[Bug c++/71825] incorrectly rejects valid C++ code with a template class inside a namespace

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71825

--- Comment #1 from Zhendong Su <su at cs dot ucdavis.edu> ---
Both the following are accepted: 

$ g++-trunk -c small1.cpp
$ cat small1.cpp
namespace N 
{
  template < class > struct A; 
}

template < class T > struct N::A 
{
  A () {} 
};
$ 
$ g++-trunk -c small2.cpp
$ cat small2.cpp 
namespace N 
{
  template < class > struct A; 
}

template < class A > struct N::A 
{
};