https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102301
--- Comment #12 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:33ed11085837e9492c6ed512931f5b6375c68ee7 commit r13-5338-g33ed11085837e9492c6ed512931f5b6375c68ee7 Author: Jonathan Wakely <jwak...@redhat.com> Date: Mon Jan 23 12:25:36 2023 +0000 libstdc++: Include std::ranges::subrange definition in <tuple> [PR102301] In order for std::make_from_tuple to work with tuple-like types, the overloads of std::get for those types must have been declared before the definition of std::make_from_tuple. That means we need to include the definition of std::ranges::subrange in <tuple>. The definitions of std::pair and its overloads of std::get are already included in <tuple>. We provide forward declarations of std::array and its std::get overloads in <tuple>. We could just declare subrange without defining it, and give ranges::get a non-deduced return type, like so: namespace ranges { enum class subrange_kind : bool { unsized, sized}; template<input_or_output_iterator I, sentinel_for<I> S, subrange_kind K> requires (K == subrange_kind::sized || !sized_sentinel_for<S, I>) class subrange; template<size_t _Num, class _It, class _Sent, subrange_kind _Kind> requires (_Num < 2) constexpr __conditional_t<_Num == 0, _It, _Sent> get(const subrange<_It, _Sent, _Kind>& __r); template<size_t _Num, class _It, class _Sent, subrange_kind _Kind> requires (_Num < 2) constexpr __conditional_t<_Num == 0, _It, _Sent> get(subrange<_It, _Sent, _Kind>&& __r) } using ranges::get; It is a bit late in the GCC 13 dev cycle to do this, so just include the right headers for now. Also add the dangling check to std::make_from_tuple added by P2255. libstdc++-v3/ChangeLog: PR libstdc++/102301 * include/bits/ranges_base.h: Include <bits/stl_iterator.h> for std::make_reverse_iterator. * include/std/tuple: Include <bits/ranges_util.h> for subrange. (make_from_tuple): Add static assertion from P2255 to diagnose dangling references. * testsuite/20_util/tuple/make_from_tuple/dangling_ref.cc: New test. * testsuite/20_util/tuple/make_from_tuple/tuple_like.cc: New test.
