https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114147
--- Comment #1 from __vic <victor.dyachenko at protonmail dot com> --- Why _ImplicitDefaultCtor is required here? template<typename _Alloc, _ImplicitDefaultCtor<is_object<_Alloc>::value, _T1, _T2> = true> _GLIBCXX20_CONSTEXPR tuple(allocator_arg_t __tag, const _Alloc& __a) : _Inherited(__tag, __a) { } Missing overload for explicit tuple(allocator_arg_t, ...)?