c++/1652: CVS20010114 tries to instantiate wrong template

[wolfgang dot bangerth at iwr dot uni-heidelberg dot de]

>Number:         1652
>Category:       c++
>Synopsis:       CVS20010114 tries to instantiate wrong template
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          rejects-legal
>Submitter-Id:   net
>Arrival-Date:   Mon Jan 15 00:56:01 PST 2001
>Closed-Date:
>Last-Modified:
>Originator:     Wolfgang Bangerth
>Release:        unknown-1.0
>Organization:
>Environment:
CVS of 20010114, on Linux
>Description:
In the following case, gcc tries to instantiate the wrong
template function (there is a specialization, so it shouldn't
even try to look at the general template):

deal.II/deal.II> cat tt.cc
  struct X {    X(int); };

  template <int dim> struct PtrDef    {    typedef X     T; };
  template <>        struct PtrDef<2> {    typedef void* T; };

  template <int dim> struct Y {
      typename PtrDef<dim>::T    f (const unsigned int = 0) const;
  };

  template <int dim>
  typename PtrDef<dim>::T  Y<dim>::f (const unsigned int) const {  return X(3); };
  template <>
  PtrDef<2>::T             Y<2>  ::f (const unsigned int) const {  return 0; };

  template struct Y<2>;
deal.II/deal.II> c++ -W -Wall -c tt.cc -o /dev/null
  tt.cc: In member function `typename PtrDef<dim>::T Y<dim>::f(unsigned int) 
     const [with int dim = 2]':
  tt.cc:15:   instantiated from here
  tt.cc:11: cannot convert `X' to `void*' in return

Note that the problem goes away if either
- I remove the 'const'ness of the function
- I remove the default argument.

Regards
  Wolfgang
>How-To-Repeat:

>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: