[PATCH 2/2] libstdc++: Implement LWG 3533 changes to foo_view::iterator::base()

[Patrick Palka <ppalka@redhat.com>]

Tested on x86_64-pc-linux-gnu, does this look OK for trunk/10/11?

libstdc++-v3/ChangeLog:

	* include/std/ranges (filter_view::_Iterator::base): Make the
	const& overload return a const reference and remove its
	constraint as per LWG 3533. Make unconditionally noexcept.
	(transform_view::_Iterator::base): Likewise.
	(elements_view::_Iterator::base): Likewise.
---
 libstdc++-v3/include/std/ranges | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index 7075fa3ae6e..bc11505c167 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -1199,9 +1199,8 @@ namespace views::__adaptor
 	    _M_parent(__parent)
 	{ }
 
-	constexpr _Vp_iter
-	base() const &
-	  requires copyable<_Vp_iter>
+	constexpr const _Vp_iter&
+	base() const & noexcept
 	{ return _M_current; }
 
 	constexpr _Vp_iter
@@ -1467,9 +1466,8 @@ namespace views::__adaptor
 	    : _M_current(std::move(__i._M_current)), _M_parent(__i._M_parent)
 	  { }
 
-	  constexpr _Base_iter
-	  base() const &
-	    requires copyable<_Base_iter>
+	  constexpr const _Base_iter&
+	  base() const & noexcept
 	  { return _M_current; }
 
 	  constexpr _Base_iter
@@ -3403,8 +3401,8 @@ namespace views::__adaptor
 	: _M_base(std::move(base))
       { }
 
-      constexpr _Vp
-      base() const& requires copy_constructible<_Vp>
+      constexpr const _Vp&
+      base() const & noexcept
       { return _M_base; }
 
       constexpr _Vp
-- 
2.31.1.442.g7e39198978