Implement LWG2952: iterator_traits should work for pointers to cv T

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@318119 91177308-0d34-0410-b5e6-96231b3b80d8

include/iterator

@@ -37,16 +37,6 @@ struct iterator_traits<T*>
     typedef random_access_iterator_tag iterator_category;
 };
 
-template<class T>
-struct iterator_traits<const T*>
-{
-    typedef ptrdiff_t difference_type;
-    typedef T value_type;
-    typedef const T* pointer;
-    typedef const T& reference;
-    typedef random_access_iterator_tag iterator_category;
-};
-
 template<class Category, class T, class Distance = ptrdiff_t,
          class Pointer = T*, class Reference = T&>
 struct iterator
@@ -494,7 +484,7 @@ template<class _Tp>
 struct _LIBCPP_TEMPLATE_VIS iterator_traits<_Tp*>
 {
     typedef ptrdiff_t difference_type;
-    typedef typename remove_const<_Tp>::type value_type;
+    typedef typename remove_cv<_Tp>::type value_type;
     typedef _Tp* pointer;
     typedef _Tp& reference;
     typedef random_access_iterator_tag iterator_category;

test/std/iterators/iterator.primitives/iterator.traits/volatile_pointer.pass.cpp

@@ -0,0 +1,28 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <iterator>
+
+// template<class T>
+// struct iterator_traits<const T*>
+
+#include <iterator>
+#include <type_traits>
+
+struct A {};
+
+int main()
+{
+    typedef std::iterator_traits<volatile A*> It;
+    static_assert((std::is_same<It::difference_type, std::ptrdiff_t>::value), "");
+    static_assert((std::is_same<It::value_type, A>::value), "");
+    static_assert((std::is_same<It::pointer, volatile A*>::value), "");
+    static_assert((std::is_same<It::reference, volatile A&>::value), "");
+    static_assert((std::is_same<It::iterator_category, std::random_access_iterator_tag>::value), "");
+}

www/cxx2a_status.html

@@ -108,7 +108,7 @@
 	<tr><td><a href="https://wg21.link/LWG2945">2945</a></td><td>Order of template parameters in optional comparisons</td><td>Albuquerque</td><td>Complete</td></tr>
 	<tr><td><a href="https://wg21.link/LWG2948">2948</a></td><td>unique_ptr does not define operator<< for stream output</td><td>Albuquerque</td><td></td></tr>
 	<tr><td><a href="https://wg21.link/LWG2950">2950</a></td><td>std::byte operations are misspecified</td><td>Albuquerque</td><td></td></tr>
-	<tr><td><a href="https://wg21.link/LWG2952">2952</a></td><td>iterator_traits should work for pointers to cv T</td><td>Albuquerque</td><td></td></tr>
+	<tr><td><a href="https://wg21.link/LWG2952">2952</a></td><td>iterator_traits should work for pointers to cv T</td><td>Albuquerque</td><td>Complete</td></tr>
 	<tr><td><a href="https://wg21.link/LWG2953">2953</a></td><td>LWG 2853 should apply to deque::erase too</td><td>Albuquerque</td><td></td></tr>
 	<tr><td><a href="https://wg21.link/LWG2958">2958</a></td><td>Moves improperly defined as deleted</td><td>Albuquerque</td><td></td></tr>
 	<tr><td><a href="https://wg21.link/LWG2964">2964</a></td><td>Apparently redundant requirement for dynamic_pointer_cast</td><td>Albuquerque</td><td></td></tr>