[Bug libstdc++/119415] flat_set::insert_range may not handle C++20 common-range

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119415

--- Comment #16 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #15)
>   template<typename _Iter>
>     using __iter_category_t
>       = typename iterator_traits<_Iter>::iterator_category;
> 
>   template<typename _InIter>
>     using _RequireInputIter =
>       __enable_if_t<is_convertible<__iter_category_t<_InIter>,
>                                  input_iterator_tag>::value>;

These are in bits/stl_iterator_base_types.h