https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95983
--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-10 branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:1cb39945993c89746b0347746bd1267de85cbc42 commit r10-9796-g1cb39945993c89746b0347746bd1267de85cbc42 Author: Patrick Palka <ppa...@redhat.com> Date: Tue Apr 20 09:18:50 2021 -0400 libstdc++: Implement P2259R1 changes [PR95983] This implements the wording changes of P2259R1 "Repairing input range adaptors and counted_iterator", which resolves LWG 3283, 3289 and 3408. The wording changes are relatively straightforward, but they require some boilerplate to implement: the changes to make a type alias "conditionally present" in some iterator class are realized by defining a base class template and an appropriately constrained partial specialization thereof that contains the type alias, and having the iterator class derive from this base class. Sometimes the relevant condition depend on members from the iterator class, but because a class is incomplete when instantiating its bases, the constraints on the partial specialization can't use anything from the iterator class. This patch works around this by hoisting these members out to the enclosing scope (e.g. transform_view::_Iterator::_Base is hoisted out to transform_view::_Base so that transform_view::__iter_cat can use it). This patch also implements the proposed resolution of LWG 3291 to rename iota_view::iterator_category to iota_view::iterator_concept, which was previously problematic due to LWG 3408. libstdc++-v3/ChangeLog: PR libstdc++/95983 * include/bits/stl_iterator.h (__detail::__move_iter_cat): Define. (move_iterator): Derive from the above in C++20 in order to conditionally define iterator_category as per P2259. (move_iterator::__base_cat): No longer used, so remove. (move_iterator::iterator_category): Remove in C++20. (__detail::__common_iter_use_postfix_proxy): Define. (common_iterator::_Proxy): Rename to ... (common_iterator:__arrow_proxy): ... this. (common_iterator::__postfix_proxy): Define as per P2259. (common_iterator::operator->): Adjust. (common_iterator::operator++): Adjust as per P2259. (iterator_traits<common_iterator>::_S_iter_cat): Define. (iterator_traits<common_iterator>::iterator_category): Change as per P2259. (__detail::__counted_iter_value_type): Define. (__detail::__counted_iter_concept): Define. (__detail::__counted_iter_cat): Define. (counted_iterator): Derive from the above three classes in order to conditionally define value_type, iterator_concept and iterator category respectively as per P2259. (counted_iterator::operator->): Define as per P2259. (incrementable_traits<counted_iterator>): Remove as per P2259. (iterator_traits<counted_iterator>): Adjust as per P2259. * include/std/ranges (__detail::__iota_view_iter_cat): Define. (iota_view::_Iterator): Derive from the above in order to conditionally define iterator_category as per P2259. (iota_view::_S_iter_cat): Rename to ... (iota_view::_S_iter_concept): ... this. (iota_view::iterator_concept): Use it to apply LWG 3291 changes. (iota_view::iterator_category): Remove. (__detail::__filter_view_iter_cat): Define. (filter_view::_Iterator): Derive from the above in order to conditionally define iterator_category as per P2259. (filter_view::_Iterator): Move to struct __filter_view_iter_cat. (filter_view::_Iterator::iterator_category): Remove. (transform_view::_Base): Define. (transform_view::__iter_cat): Define. (transform_view::_Iterator): Derive from the above in order to conditionally define iterator_category as per P2259. (transform_view::_Iterator::_Base): Just alias transform_view::_Base. (transform_view::_Iterator::_S_iter_cat): Move to struct transform_view::__iter_cat. (transform_view::_Iterator::iterator_category): Remove. (transform_view::_Sentinel::_Base): Just alias transform_view::_Base. (join_view::_Base): Define. (join_view::_Outer_iter): Define. (join_view::_Inner_iter): Define. (join_view::_S_ref_is_glvalue): Define. (join_view::__iter_cat): Define. (join_view::_Iterator): Derive from it in order to conditionally define iterator_category as per P2259. (join_view::_Iterator::_Base): Just alias join_view::_Base. (join_view::_Iterator::_S_ref_is_glvalue): Just alias join_view::_S_ref_is_glvalue. (join_view::_Iterator::_S_iter_cat): Move to struct transform_view::__iter_cat. (join_view::_Iterator::_Outer_iter): Just alias join_view::_Outer_iter. (join_view::_Iterator::_Inner_iter): Just alias join_view::_Inner_iter. (join_view::_Iterator::iterator_category): Remove. (join_view::_Sentinel::_Base): Just alias join_view::_Base. (__detail::__split_view_outer_iter_cat): Define. (__detail::__split_view_inner_iter_cat): Define. (split_view::_Base): Define. (split_view::_Outer_iter): Derive from __split_view_outer_iter_cat in order to conditionally define iterator_category as per P2259. (split_view::_Outer_iter::iterator_category): Remove. (split_view::_Inner_iter): Derive from __split_view_inner_iter_cat in order to conditionally define iterator_category as per P2259. (split_view::_Inner_iter::_S_iter_cat): Move to __split_view_inner_iter_cat. (split_view::_Inner_iter::iterator_category): Remove. (elements_view::_Base): Define. (elements_view::__iter_cat): Define. (elements_view::_Iterator): Derive from the above in order to conditionall define iterator_category as per P2259. (elements_view::_Iterator::_Base): Just alias elements_view::_Base. (elements_view::_Iterator::_S_iter_concept) (elements_view::_Iterator::iterator_concept): Define as per P2259. (elements_view::_Iterator::iterator_category): Remove. (elements_view::_Sentinel::_Base): Just alias elements_view::_Base. * testsuite/24_iterators/headers/iterator/synopsis_c++20.cc: Adjust constraints on iterator_traits<counted_iterator>. * testsuite/std/ranges/p2259.cc: New test. (cherry picked from commit 902b40c797a86f76791c32d537ba06dff5f1ba27)
