libstdc++: Implement LWG 3535 changes to ranges::join_view

libstdc++-v3/ChangeLog:

	* include/std/ranges (join_view::__iter_cat::_S_iter_cat): Adjust
	criteria for returning bidirectional_iterator_tag as per LWG 3535.
	(join_view::_Iterator::_S_iter_concept): Likewise.

diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index 273699a..c1519c7 100644 (file)
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -2523,7 +2523,8 @@ namespace views::__adaptor
            using _OuterCat = typename iterator_traits<_Outer_iter>::iterator_category;
            using _InnerCat = typename iterator_traits<_Inner_iter>::iterator_category;
            if constexpr (derived_from<_OuterCat, bidirectional_iterator_tag>
-                         && derived_from<_InnerCat, bidirectional_iterator_tag>)
+                         && derived_from<_InnerCat, bidirectional_iterator_tag>
+                         && common_range<range_reference_t<_Base<_Const>>>)
              return bidirectional_iterator_tag{};
            else if constexpr (derived_from<_OuterCat, forward_iterator_tag>
                               && derived_from<_InnerCat, forward_iterator_tag>)
@@ -2575,7 +2576,8 @@ namespace views::__adaptor
          {
            if constexpr (_S_ref_is_glvalue
                          && bidirectional_range<_Base>
-                         && bidirectional_range<range_reference_t<_Base>>)
+                         && bidirectional_range<range_reference_t<_Base>>
+                         && common_range<range_reference_t<_Base>>)
              return bidirectional_iterator_tag{};
            else if constexpr (_S_ref_is_glvalue
                               && forward_range<_Base>