[committed] libstdc++: decay in viewable_range should be remove_cvref (LWG 3375)

[Jonathan Wakely]

        * include/bits/stl_algobase.h (__iter_swap, __iter_swap<true>): Remove
        redundant _GLIBCXX20_CONSTEXPR.

Tested powerpc64le-linux, committed to master.


commit 26eae9ac2bf75a26a419dc1e47a067c66331fb74
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Thu Feb 6 11:30:30 2020 +0000

    libstdc++: decay in viewable_range should be remove_cvref (LWG 3375)
    
            * include/bits/stl_algobase.h (__iter_swap, __iter_swap<true>): 
Remove
            redundant _GLIBCXX20_CONSTEXPR.

diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index ea558c76c9d..860f7283be5 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -92,7 +92,7 @@ namespace ranges
   /// A range which can be safely converted to a view.
   template<typename _Tp>
     concept viewable_range = range<_Tp>
-      && (safe_range<_Tp> || view<decay_t<_Tp>>);
+      && (safe_range<_Tp> || view<remove_cvref_t<_Tp>>);
 
   namespace __detail
   {