[Bug c++/35815] New: partial specialization of variadic templates with different order of parameter results in different semantics

[sultansharem at gmx dot ch]

the static 2nd static assertion in x() fails. if the other partial
specialization of template d is used, the code works as expected. As you can
see the only difference between these d's is, that the T parameter is at a
different position which shouldn't make a difference to the outcome of typedef
T t;
<code>
template <class...>
   struct p;

template <class A, class B> struct i { typedef i t; };

template <class I> struct d;
template <class I> struct n;

template <class... L, class T, class... R> struct n<i<p<L...>, p<T, R...> > > :
i<p<L..., T>, p<R...> > {};

#if 1
template <class... L, class T, class... R>
    struct d<i<p<L...>, p<T, R...> > >
    {
        typedef T   t;
    };

#else
template <class T, class... L, class... R>
    struct d<i<p<L...>, p<T, R...> > >
    {
        typedef T   t;
    };
#endif

template <class A, class B> struct is_same  { static const bool v=false; };

template <class A> struct is_same<A, A>     { static const bool v=true; };

void x()
{
    typedef i<p<>, p<short, int, bool> >    i0;
    static_assert(is_same<d<i0>::t, short>::v,"");

    typedef n<i0>::t    i1;
    static_assert(is_same<d<i1>::t, int>::v,"");
}


-- 
           Summary: partial specialization of variadic templates with
                    different order of parameter results in different
                    semantics
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: sultansharem at gmx dot ch


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35815