[Bug c++/63885] New: ICE in static assert of constexpr forwarding xvalue container member rvalue reference

["listcrawler at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63885

            Bug ID: 63885
           Summary: ICE in static assert of constexpr forwarding xvalue
                    container member rvalue reference
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: listcrawler at gmail dot com

Created attachment 33983
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33983&action=edit
preprocessed source file

Internal compiler error in static assert of constexpr forwarding xvalue
container member rvalue reference. 

g++ 4.8 and 4.9 passes, but trunk built from r217559 on ubuntu 14.04 fails
compilation with

$ g++-trunk -std=c++11 -Wall -Wextra constexpr_static_assert.ii
constexpr_static_assert.cpp:50:39:   in constexpr expansion of âget<0, S<int&&>
>((* & S<int&&>((* &1))))â
constexpr_static_assert.cpp:35:35:   in constexpr expansion of â__get<0,
T>::value<S<int&&>&&>((* & std::forward<S<int&&> >((* & arg))))â
constexpr_static_assert.cpp:50:44: internal compiler error: in
verify_ctor_sanity, at cp/constexpr.c:1779
 static_assert (get <0> (S <int &&> (1)) == 1, ""); // g++ 4.9 passes, g++
trunk r217559 fails

...

///////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////
//
// source
//

#include <utility>

using namespace std;

///////////////////////////////////////////////////////////////////////////////

template <typename C> struct member_forward
{
    typedef typename remove_reference <C>::type::type T;
    typedef typename conditional
    <
        is_lvalue_reference <C &&>::value && not is_reference <T>::value,
        typename add_lvalue_reference <T>::type,
        T
    >::type type;
};

template <typename C> using member_forward_t = typename member_forward
<C>::type;

///////////////////////////////////////////////////////////////////////////////

template <int  , typename  > struct __get;
template <       typename T> struct __get <0, T> 
{ 
    constexpr static auto value (T arg) 
     -> decltype ((forward <member_forward_t <T>> (arg.t))) 
    {  
        return     forward <member_forward_t <T>> (arg.t); 
    } 
};

template <int N, typename T> constexpr auto get (T && arg)
 -> decltype (__get <N, T &&>::value (forward <T> (arg)))
{
    return    __get <N, T &&>::value (forward <T> (arg));
}

///////////////////////////////////////////////////////////////////////////////

template <typename T> struct S
{
    typedef T type;
    T t;

    template <typename U> constexpr S (U && u) : t (forward <U> (u)) {} 
};

///////////////////////////////////////////////////////////////////////////////

static_assert (get <0> (S <int &&> (1)) == 1, ""); // g++ 4.9 passes, g++ trunk
r217559 fails

int main () {}

///////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////