[PATCH] libstdc++: Implement LWG 3595 changes to common_iterator

[Patrick Palka via Gcc-patches]

Tested on x86_64-pc-linux-gnu, does this look OK for trunk and branches?

libstdc++-v3/ChangeLog:

        * include/bits/stl_iterator.h (common_iterator::__arrow_proxy):
        Make fully constexpr.
        (common_iterator::__postfix_proxy): Likewise.
---
 libstdc++-v3/include/bits/stl_iterator.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/libstdc++-v3/include/bits/stl_iterator.h 
b/libstdc++-v3/include/bits/stl_iterator.h
index 8afd6756613..da3c8d5bd97 100644
--- a/libstdc++-v3/include/bits/stl_iterator.h
+++ b/libstdc++-v3/include/bits/stl_iterator.h
@@ -1821,13 +1821,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       iter_value_t<_It> _M_keep;
 
-      __arrow_proxy(iter_reference_t<_It>&& __x)
+      constexpr __arrow_proxy(iter_reference_t<_It>&& __x)
       : _M_keep(std::move(__x)) { }
 
       friend class common_iterator;
 
     public:
-      const iter_value_t<_It>*
+      constexpr const iter_value_t<_It>*
       operator->() const noexcept
       { return std::__addressof(_M_keep); }
     };
@@ -1836,13 +1836,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       iter_value_t<_It> _M_keep;
 
-      __postfix_proxy(iter_reference_t<_It>&& __x)
+      constexpr __postfix_proxy(iter_reference_t<_It>&& __x)
       : _M_keep(std::forward<iter_reference_t<_It>>(__x)) { }
 
       friend class common_iterator;
 
     public:
-      const iter_value_t<_It>&
+      constexpr const iter_value_t<_It>&
       operator*() const noexcept
       { return _M_keep; }
     };
-- 
2.33.1.711.g9d530dc002