[Bug c++/117727] __builtin_bit_cast with target type nullptr_t unimplemented

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117727

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
nullptr_t can only contain 0. So it is undefined if converted from a different
value. For constexpr it has to be rejected.