[Bug c++/19188] friend funtion inside a template class seems to have a problem

["lerdsuwa at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From lerdsuwa at gcc dot gnu dot org  2004-12-31 13:23 -------
The 'typename' keyword is required because later C++ introduces a lot more
features.  Those that interfere with your code are partial specialization 
and specialization.  For example, you can now have specialization

  template <> class tstack<bool> {
    int link;
    ...
  };

Then when you declare

  tstack<bool> t;

it will use the above declaration, where 'link' is now a member data
instead of a nested class.  So the code

  tstack<T>::link* p;

which could be interpreted as declaring a variable which is a pointer to type
'tstack<T>::link' if 'T' is 'int'.  But when 'T' is 'bool' it could means
multiplying a member data with another variable named 'p'.

To resolve the ambiguity, later C++ requires the 'typename' keyword to
treat as pointer declaration, otherwise it will be treated as muliplication.
Older C++ books don't have this 'typename' keyword but newer good books 
from respected authors coming out in the last few years should.  
(Many new C++ books are still wrong).

I know the parser error message could be improved, and there are plenty of
bug reports elsewhere about it.

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19188