libstdc++: Implement LWG 3591-3592 changes to split_view

libstdc++-v3/ChangeLog:

	* include/std/ranges (split_view::base): Add forward_range
	constraint as per LWG 3591.
	(split_view::begin, lazy_split_view::end): Also check
	simpleness of _Pattern as per LWG 3592.

(cherry picked from commit 2d3ac6039074832978ce9bcd41ba93ef4812458f)

diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index 52ca908075985b714ac1b859b493d8dad238d2c7..f55ee15e1b14574db0a5c33aad4fdf626595021a 100644 (file)
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -3072,7 +3072,7 @@ namespace views::__adaptor
          { return _M_i_current(); }
 
          constexpr iterator_t<_Base>
-         base() &&
+         base() && requires forward_range<_Vp>
          { return std::move(_M_i_current()); }
 
          constexpr decltype(auto)
@@ -3166,8 +3166,11 @@ namespace views::__adaptor
       begin()
       {
        if constexpr (forward_range<_Vp>)
-         return _OuterIter<__detail::__simple_view<_Vp>>{
-             this, ranges::begin(_M_base)};
+         {
+           constexpr bool __simple
+             = __detail::__simple_view<_Vp> && __detail::__simple_view<_Pattern>;
+           return _OuterIter<__simple>{this, ranges::begin(_M_base)};
+         }
        else
          {
            _M_current = ranges::begin(_M_base);
@@ -3184,8 +3187,9 @@ namespace views::__adaptor
       constexpr auto
       end() requires forward_range<_Vp> && common_range<_Vp>
       {
-       return _OuterIter<__detail::__simple_view<_Vp>>{
-           this, ranges::end(_M_base)};
+       constexpr bool __simple
+         = __detail::__simple_view<_Vp> && __detail::__simple_view<_Pattern>;
+       return _OuterIter<__simple>{this, ranges::end(_M_base)};
       }
 
       constexpr auto