https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100456
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> --- The CWG issue is http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#2237 and the C++20 standard even calls it out as an incompatibility with C++17.
