Extract is_error_code_enum, is_error_condition_enum into their own headers

include/boost/system/error_code.hpp

@@ -10,6 +10,8 @@
 //
 //  See library home page at http://www.boost.org/libs/system
 
+#include <boost/system/is_error_code_enum.hpp>
+#include <boost/system/is_error_condition_enum.hpp>
 #include <boost/system/api_config.hpp>
 #include <boost/system/detail/config.hpp>
 #include <boost/cstdint.hpp>
@@ -40,18 +42,6 @@ class error_code;         // values defined by the operating system
 class error_condition;    // portable generic values defined below, but ultimately
                           // based on the POSIX standard
 
-// "Concept" helpers
-
-template<class T> struct is_error_code_enum
-{
-    static const bool value = false;
-};
-
-template<class T> struct is_error_condition_enum
-{
-    static const bool value = false;
-};
-
 // Generic error_conditions
 
 namespace errc

include/boost/system/is_error_code_enum.hpp

@@ -0,0 +1,30 @@
+#ifndef BOOST_SYSTEM_IS_ERROR_CODE_ENUM_HPP_INCLUDED
+#define BOOST_SYSTEM_IS_ERROR_CODE_ENUM_HPP_INCLUDED
+
+//  Copyright Beman Dawes 2006, 2007
+//  Copyright Christoper Kohlhoff 2007
+//  Copyright Peter Dimov 2017, 2018
+//
+//  Distributed under the Boost Software License, Version 1.0. (See accompanying
+//  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+//  See library home page at http://www.boost.org/libs/system
+
+namespace boost
+{
+
+namespace system
+{
+
+class error_code;
+
+template<class T> struct is_error_code_enum
+{
+    static const bool value = false;
+};
+
+} // namespace system
+
+} // namespace boost
+
+#endif // #ifndef BOOST_SYSTEM_IS_ERROR_CODE_ENUM_HPP_INCLUDED

include/boost/system/is_error_condition_enum.hpp

@@ -0,0 +1,30 @@
+#ifndef BOOST_SYSTEM_IS_ERROR_CONDITION_ENUM_HPP_INCLUDED
+#define BOOST_SYSTEM_IS_ERROR_CONDITION_ENUM_HPP_INCLUDED
+
+//  Copyright Beman Dawes 2006, 2007
+//  Copyright Christoper Kohlhoff 2007
+//  Copyright Peter Dimov 2017, 2018
+//
+//  Distributed under the Boost Software License, Version 1.0. (See accompanying
+//  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+//  See library home page at http://www.boost.org/libs/system
+
+namespace boost
+{
+
+namespace system
+{
+
+class error_condition;
+
+template<class T> struct is_error_condition_enum
+{
+    static const bool value = false;
+};
+
+} // namespace system
+
+} // namespace boost
+
+#endif // #ifndef BOOST_SYSTEM_IS_ERROR_CONDITION_ENUM_HPP_INCLUDED