https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111357
--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Reduced to remove <utility>:
namespace std {
template<typename _Tp, _Tp... _Idx>
struct integer_sequence
{ };
template<typename _Tp, _Tp _Num>
using make_integer_sequence
= integer_sequence<_Tp, __integer_pack(_Num)...>;
}
using std::integer_sequence;
using std::make_integer_sequence;
template<int... V>
void g(integer_sequence<int,V...>)
{}
template<typename ...T>
struct c1
{
static constexpr int value = 1;
constexpr operator int() { return value; }
};
template<typename T>
struct R
{
using S = make_integer_sequence<int,c1<T>{}>;
R() noexcept(noexcept(g(S())))
{}
};
int main()
{
R<int>();
}
This certainly seems like a front end bug not a libstdc++ one, but the library
can make it work by casting _Tp _Num to its own type:
template<typename _Tp, _Tp _Num>
using make_integer_sequence
= integer_sequence<_Tp, __integer_pack(_Tp(_Num))...>;
This should not be needed, but makes it work.
