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.
33ed110858