https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69905
--- Comment #8 from Jonathan Wakely <redi at gcc dot gnu.org> --- The testcase in comment 2 (the only one in the bug that's actually correct!) works now, fixed by r258157 for Bug 84671. The problem in comment 7 still exists, the corrected testcase is: #include <chrono> int main() { using namespace std::chrono_literals; auto time = operator""s(0x8000'0000'0000'0000'0000'0000ULL); static_assert(std::is_same<decltype(time)::rep, unsigned long long>(), ""); }