Add detail/is_scoped_enum.hpp

include/boost/endian/detail/is_scoped_enum.hpp

@@ -0,0 +1,35 @@
+#ifndef BOOST_ENDIAN_DETAIL_IS_SCOPED_ENUM_HPP_INCLUDED
+#define BOOST_ENDIAN_DETAIL_IS_SCOPED_ENUM_HPP_INCLUDED
+
+// Copyright 2020 Peter Dimov
+//
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/type_traits/conditional.hpp>
+#include <boost/type_traits/is_enum.hpp>
+#include <boost/type_traits/is_convertible.hpp>
+
+namespace boost
+{
+namespace endian
+{
+namespace detail
+{
+
+template<class T> struct negation: boost::integral_constant<bool, !T::value> {};
+
+template<class T> struct is_scoped_enum:
+    boost::conditional<
+        boost::is_enum<T>::value,
+        negation<boost::is_convertible<T, int>>,
+        boost::false_type
+    >::type
+{
+};
+
+} // namespace detail
+} // namespace endian
+} // namespace boost
+
+#endif  // BOOST_ENDIAN_DETAIL_IS_SCOPED_ENUM_HPP_INCLUDED