detail/iterator_traits: inherit from std::iterator_traits

Using Boost.Move breaks range-v3, since the latter specializes
std::iterator_traits for its custom iterators.

include/boost/move/detail/iterator_traits.hpp

@@ -23,6 +23,7 @@
 #endif
 
 #include <cstddef>
+#include <iterator>
 #include <boost/move/detail/type_traits.hpp>
 
 #include <boost/move/detail/std_ns_begin.hpp>
@@ -38,41 +39,47 @@ struct contiguous_iterator_tag;
 BOOST_MOVE_STD_NS_END
 #include <boost/move/detail/std_ns_end.hpp>
 
-namespace boost{  namespace movelib{
+namespace boost{  namespace move_detail{
 
-template<class Iterator>
+// SFINAE correct version of std::iterator_traits, see:
+// https://cplusplus.github.io/LWG/issue2951
+template <typename T, typename = void>
 struct iterator_traits
 {
-   typedef typename Iterator::difference_type   difference_type;
-   typedef typename Iterator::value_type        value_type;
-   typedef typename Iterator::pointer           pointer;
-   typedef typename Iterator::reference         reference;
-   typedef typename Iterator::iterator_category iterator_category;
-   typedef typename boost::move_detail::make_unsigned<difference_type>::type size_type;
 };
 
-template<class T>
-struct iterator_traits<T*>
+template <typename T>
+struct iterator_traits<T, typename enable_if_c<!is_pointer<T>::value, void>::type>
+  : std::iterator_traits<T>
 {
-   typedef std::ptrdiff_t                    difference_type;
-   typedef T                                 value_type;
-   typedef T*                                pointer;
-   typedef T&                                reference;
-   typedef std::random_access_iterator_tag   iterator_category;
+   typedef typename std::iterator_traits<T>::difference_type difference_type;
+   typedef typename std::iterator_traits<T>::pointer pointer;
+   typedef typename std::iterator_traits<T>::reference reference;
+   typedef typename std::iterator_traits<T>::iterator_category iterator_category;
+   typedef typename std::iterator_traits<T>::value_type value_type;
+
    typedef typename boost::move_detail::make_unsigned<difference_type>::type size_type;
 };
 
-template<class T>
-struct iterator_traits<const T*>
+template <typename T>
+struct iterator_traits<T*>
+  : std::iterator_traits<T*>
 {
-   typedef std::ptrdiff_t                    difference_type;
-   typedef T                                 value_type;
-   typedef const T*                          pointer;
-   typedef const T&                          reference;
-   typedef std::random_access_iterator_tag   iterator_category;
+   typedef typename std::iterator_traits<T*>::difference_type difference_type;
+   typedef typename std::iterator_traits<T*>::pointer pointer;
+   typedef typename std::iterator_traits<T*>::reference reference;
+   typedef typename std::iterator_traits<T*>::iterator_category iterator_category;
+   typedef typename std::iterator_traits<T*>::value_type value_type;
+
    typedef typename boost::move_detail::make_unsigned<difference_type>::type size_type;
 };
+} // namespace move_detail {
 
-}} //namespace boost {  namespace movelib{
+namespace movelib{
+template <typename T>
+struct iterator_traits : move_detail::iterator_traits<T>
+{
+};
+}} // namespace boost { namespace move_lib {
 
 #endif //#ifndef BOOST_MOVE_DETAIL_ITERATOR_TRAITS_HPP

include/boost/move/detail/type_traits.hpp

@@ -788,6 +788,18 @@ struct is_class
    static const bool value = is_class_or_union<T>::value && ! is_union<T>::value;
 };
 
+//////////////////////////////////////
+//          is_object
+//////////////////////////////////////
+
+template <class T>
+struct is_object
+{
+    static const bool value = is_scalar<T>::value ||
+                              is_array<T>::value  ||
+                              is_union<T>::value  ||
+                              is_class<T>::value;
+};
 
 //////////////////////////////////////
 //             is_arithmetic