https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80387
--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> --- This code isn't strictly ice-on-invalid, it's just completely crazy and no compiler will ever handle it, because it asks for std::index_sequence<0, 1, 2, 3, ..., 18446744073709551614>. We could add a static_assert( N != size_t(-1), "" ) but that wouldn't help for equally crazy cases like make_index_sequence<size_t(-2)>. Maybe we should just reject anything over ULONG_MAX/2.
