Implement the first part of N4258 - allocator_traits<X>::is_always_equal. Also fixes PR#23723

llvm-svn: 238848

1 files changed, 14 insertions, 0 deletions

diff --git a/libcxx/include/scoped_allocator b/libcxx/include/scoped_allocator
index aa8bece6d33..5864689d1f2 100644
--- a/libcxx/include/scoped_allocator
+++ b/libcxx/include/scoped_allocator
@@ -38,6 +38,7 @@ public:
     typedef see below propagate_on_container_copy_assignment;
     typedef see below propagate_on_container_move_assignment;
     typedef see below propagate_on_container_swap;
+    typedef see below is_always_equal;
 
     template <class Tp>
         struct rebind
@@ -170,6 +171,14 @@ struct __get_poc_swap<_A0, _Allocs...>
         __get_poc_swap<_Allocs...>::value;
 };
 
+template <class _A0, class ..._Allocs>
+struct __get_poc_always_equal<_A0, _Allocs...>
+{
+    static const bool value =
+        allocator_traits<_A0>::is_always_equal::value ||
+        __get_poc_always_equal<_Allocs...>::value;
+};
+
 template <class ..._Allocs>
 class __scoped_allocator_storage;
 
@@ -397,6 +406,11 @@ public:
                 bool,
                 __get_poc_swap<outer_allocator_type, _InnerAllocs...>::value
             > propagate_on_container_swap;
+    typedef integral_constant
+            <
+                bool,
+                __get_poc_always_equal<outer_allocator_type, _InnerAllocs...>::value
+            > is_always_equal;
 
     template <class _Tp>
     struct rebind