Re: c++/3831: problem with forward declaration of function taking a reference to a generic member

[Nathanael Nerode <neroden@twcny.rr.com>]

The following reply was made to PR c++/3831; it has been noted by GNATS.

From: Nathanael Nerode <neroden@twcny.rr.com>
To: gcc-gnats@gcc.gnu.org, gcc-prs@gcc.gnu.org,
   lachaume@laog.obs.ujf.grenoble.fr, gcc-bugs@gcc.gnu.org, nobody@gcc.gnu.org
Cc:  
Subject: Re: c++/3831: problem with forward declaration of function taking a reference to a generic member
Date: Fri, 3 Jan 2003 08:26:34 -0500

 3.4 behaves totally differently on the examples.
 
 I believe the stated problem is fixed.  However, I need to verify that the 
 two changes I made to the examples to get them to work are, in fact, fixes 
 needed to make the code legal.  (If not, I have revealed other bugs...)
 
 If the definition of struct A is moved above the forward declaration of g, 
 and the use of 'typename' inside the formal arguments is removed in all 
 cases, all is well.
 --
 template <typename u> struct A;
 
 template <typename u> struct A {
     template <typename v> struct B { };
  };
  
 template <typename u, typename v> void g(A<u>::B<v>&);
 
 template <typename u, typename v> void g(A<u>::B<v>&);
   
 int main() {
     A<int>::B<float> b;
     g<int, float>(b);
  }
 --
 
 I believe that the definition of struct A needs to be above the declaration 
 of g because otherwise B isn't declared at the time of declaration of g.  I 
 can't figure out a way to declare B before the definition of A.  If there is 
 one in the C++ standard, I'll be happy to use it and see if that works.
 
 I don't know why the 'typename' has to be removed from inside the arguments.
 But it it isn't removed, g++ 3.4 does the same thing as it does if B isn't 
 declared before g: it decides that g is not a function (calls it a "variable 
 or field").
 
 --Nathanael