[PATCH] libstdc++: Implement LWG 3517 and 3520 for transform_view/join_view

[Jonathan Wakely]

On 04/05/21 21:42 -0400, Patrick Palka via Libstdc++ wrote:
>Tested on x86_64-pc-linux-gnu, does this look OK for trunk and perhaps
>10/11?

Yes, for all branches.

>libstdc++-v3/ChangeLog:
>
>	* include/std/ranges (transform_view::_Iterator::iter_swap):
>	Remove as per LWG 3520.
>	(join_view::_Iterator::iter_swap): Add indirectly_swappable
>	constraint as per LWG 3517.
>---
> libstdc++-v3/include/std/ranges | 7 +------
> 1 file changed, 1 insertion(+), 6 deletions(-)
>
>diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
>index 4a7ca49b45d..f21e08a36e3 100644
>--- a/libstdc++-v3/include/std/ranges
>+++ b/libstdc++-v3/include/std/ranges
>@@ -1581,12 +1581,6 @@ namespace views::__adaptor
> 	      return *__i;
> 	  }
>
>-	  friend constexpr void
>-	  iter_swap(const _Iterator& __x, const _Iterator& __y)
>-	    noexcept(noexcept(ranges::iter_swap(__x._M_current, __y._M_current)))
>-	    requires indirectly_swappable<_Base_iter>
>-	  { return ranges::iter_swap(__x._M_current, __y._M_current); }
>-
> 	  friend _Iterator<!_Const>;
> 	  template<bool> friend struct _Sentinel;
> 	};
>@@ -2520,6 +2514,7 @@ namespace views::__adaptor
> 	  friend constexpr void
> 	  iter_swap(const _Iterator& __x, const _Iterator& __y)
> 	    noexcept(noexcept(ranges::iter_swap(__x._M_inner, __y._M_inner)))
>+	    requires indirectly_swappable<_Inner_iter>
> 	  { return ranges::iter_swap(__x._M_inner, __y._M_inner); }
>
> 	  friend _Iterator<!_Const>;
>-- 
>2.31.1.442.g7e39198978
>