Changes requested from code review.

include/nlohmann/detail/iterators/iterator_traits.hpp

@@ -3,16 +3,17 @@
 #include <iterator> // random_access_iterator_tag
 
 #include <nlohmann/detail/meta/void_t.hpp>
+#include <nlohmann/detail/meta/cpp_future.hpp>
 
 namespace nlohmann
 {
 namespace detail
 {
-template <class It, class = void>
-struct _iterator_types {};
+template <typename It, typename = void>
+struct iterator_types {};
 
-template <class It>
-struct _iterator_types<
+template <typename It>
+struct iterator_types<
     It,
     void_t<typename It::difference_type, typename It::value_type, typename It::pointer,
            typename It::reference, typename It::iterator_category>> {
@@ -23,25 +24,26 @@ struct _iterator_types<
   using iterator_category = typename It::iterator_category;
 };
 
-template <class Iter>
-struct iterator_traits : _iterator_types<Iter> {};
+// This is required as some compilers implement std::iterator_traits in a way that
+// doesn't work with SFINAE. See https://github.com/nlohmann/json/issues/1341.
+template <typename T, typename = void>
+struct iterator_traits
+{
+};
 
-template <class T>
-struct iterator_traits<T*> {
-  typedef std::random_access_iterator_tag iterator_category;
-  typedef T value_type;
-  typedef ptrdiff_t difference_type;
-  typedef T* pointer;
-  typedef T& reference;
+template <typename T>
+struct iterator_traits<T, enable_if_t<!std::is_pointer<T>::value>>
+  : iterator_types<T>
+{
 };
 
-template <class T>
-struct iterator_traits<const T*> {
+template <typename T>
+struct iterator_traits<T*, enable_if_t<std::is_object<T>::value>> {
   typedef std::random_access_iterator_tag iterator_category;
   typedef T value_type;
   typedef ptrdiff_t difference_type;
-  typedef const T* pointer;
-  typedef const T& reference;
+  typedef T* pointer;
+  typedef T& reference;
 };
 }
 }
\ No newline at end of file

single_include/nlohmann/json.hpp

@@ -344,16 +344,18 @@ template <typename ...Ts> using void_t = typename make_void<Ts...>::type;
 } // namespace detail
 }  // namespace nlohmann
 
+// #include <nlohmann/detail/meta/cpp_future.hpp>
+
 
 namespace nlohmann
 {
 namespace detail
 {
-template <class It, class = void>
-struct _iterator_types {};
+template <typename It, typename = void>
+struct iterator_types {};
 
-template <class It>
-struct _iterator_types <
+template <typename It>
+struct iterator_types <
     It,
     void_t<typename It::difference_type, typename It::value_type, typename It::pointer,
     typename It::reference, typename It::iterator_category >>
@@ -365,27 +367,27 @@ struct _iterator_types <
     using iterator_category = typename It::iterator_category;
 };
 
-template <class Iter>
-struct iterator_traits : _iterator_types<Iter> {};
+// This is required due to https://github.com/nlohmann/json/issues/1341 - where some
+// compilers implement std::iterator_traits in a way that doesn't work with SFINAE.
+template <typename T, typename = void>
+struct iterator_traits
+{
+};
 
-template <class T>
-struct iterator_traits<T*>
+template <typename T>
+struct iterator_traits < T, enable_if_t < !std::is_pointer<T>::value >>
+            : iterator_types<T>
 {
-    typedef std::random_access_iterator_tag iterator_category;
-    typedef T value_type;
-    typedef ptrdiff_t difference_type;
-    typedef T* pointer;
-    typedef T& reference;
 };
 
-template <class T>
-struct iterator_traits<const T*>
+template <typename T>
+struct iterator_traits<T*, enable_if_t<std::is_object<T>::value>>
 {
     typedef std::random_access_iterator_tag iterator_category;
     typedef T value_type;
     typedef ptrdiff_t difference_type;
-    typedef const T* pointer;
-    typedef const T& reference;
+    typedef T* pointer;
+    typedef T& reference;
 };
 }
 }