[Bug c++/46061] New: Variadic Template Templates: not expandable into fixed-size argument list, Implementation Gap.

["andreas.milton.m at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46061

           Summary: Variadic Template Templates: not expandable into
                    fixed-size argument list, Implementation Gap.
           Product: gcc
           Version: 4.5.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: andreas.milton.m@gmail.com


Created attachment 22073
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22073
full demo for bug ( .ii-file <14 lines)

The following struct "type_list" marks a list of types, which is constructed as
a template template class with a variadic type list of template arguments:

template <typename H, template <typename> class T, template <typename> class...
R> 
struct type_list 
{ 
   typedef type_list< T<H>, R... > tail; 
}; 

template<typename H, template<typename> class T> 
struct type_list<H,T> {};


The code (attached as variadic_templ_templ.ii) produces the following
error-message (identical for gcc 4.4 and 4.5.1):

"sorry, unimplemented: cannot expand ‘template<class> class ... R ...’ into a
fixed-length argument list"

No other flags than -v -save-temps -Wall -std=c++0x were used.