[Bug regression/21740] New: template mismatch in 3.4 and 4.1

["monge at sns dot it" <gcc-bugzilla at gcc dot gnu dot org>]

hi, the following code compiled properly in 3.3.5:

#begin code

 /* bind 2nd parameter in a 2 parameters metafunction */
 template< template<typename A, typename B> class MetaFunc, typename B>
 struct bind_2 {
    template<typename T>
    struct bound {
        typedef typename MetaFunc<T,B>::type type;      
  }; };
 template<typename A, typename B>
 struct Fx{
    /* refer int 2 steps to Fx<A,int> */
    typedef typename bind_2< Fx, int >::template bound<A>::type type;
  };    
 template<typename A>
 struct Fx<A,int>{
    typedef double type;
  };

#end code

When compiling with gcc 3.4.3 or 4.1 (recent CVS) i get:
bug.cpp:16: error: type/value mismatch at argument 1 in template parameter list
for `template<template<class A, class B> class MetaFunc, class B> struct bind_2'
bug.cpp:16: error:   expected a class template, got `Fx<A, B>'
bug.cpp:16: error: expected unqualified-id before "template"

The strange thing is that if Fx is defined bi-recursively (instead that
recursively) it compiles on 3.4 and 4.1 too:
This is the working workaround:

#begin code

 template<typename A, typename B>
 struct Fx;
 template<typename A, typename B>
 struct Fy;    
 template<typename A, typename B>
 struct Fx{
    typedef typename bind_2< Fy, int >::template bound<A>::type type;
  };
 template<typename A>
 struct Fx<A,int>{
    typedef double type;
  };    
 template<typename A, typename B>
 struct Fy{
    typedef typename bind_2< Fx, int >::template bound<A>::type type;
  };
 template<typename A>
 struct Fy<A,int>{
    typedef double type;
  };

#end code

-- 
           Summary: template mismatch in 3.4 and 4.1
           Product: gcc
           Version: 3.4.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: regression
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: monge at sns dot it
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i386-pc-linux
  GCC host triplet: i386-pc-linux
GCC target triplet: i386-pc-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21740