[Bug libstdc++/114147] tuple allocator-extended constructor requires non-explicit default constructor

[victor.dyachenko at protonmail dot com via Gcc-bugs]

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, ...)?