From 72ea1ef8462a94cb23a838dc570319f1249fea51 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Thu, 27 Aug 2020 01:21:56 +0300
Subject: [PATCH] Extract enable_if into its own header

---
 include/boost/system/detail/enable_if.hpp | 32 +++++++++++++++++++++++
 include/boost/system/error_code.hpp       | 12 +--------
 2 files changed, 33 insertions(+), 11 deletions(-)
 create mode 100644 include/boost/system/detail/enable_if.hpp

diff --git a/include/boost/system/detail/enable_if.hpp b/include/boost/system/detail/enable_if.hpp
new file mode 100644
index 0000000..7f3d70b
--- /dev/null
+++ b/include/boost/system/detail/enable_if.hpp
@@ -0,0 +1,32 @@
+#ifndef BOOST_SYSTEM_DETAIL_ENABLE_IF_HPP_INCLUDED
+#define BOOST_SYSTEM_DETAIL_ENABLE_IF_HPP_INCLUDED
+
+// Copyright 2020 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0
+// http://www.boost.org/LICENSE_1_0.txt
+
+namespace boost
+{
+
+namespace system
+{
+
+namespace detail
+{
+
+template<bool C, class T = void> struct enable_if
+{
+    typedef T type;
+};
+
+template<class T> struct enable_if<false, T>
+{
+};
+
+} // namespace detail
+
+} // namespace system
+
+} // namespace boost
+
+#endif // #ifndef BOOST_SYSTEM_DETAIL_ENABLE_IF_HPP_INCLUDED
diff --git a/include/boost/system/error_code.hpp b/include/boost/system/error_code.hpp
index 1dccb4f..2ca6b92 100644
--- a/include/boost/system/error_code.hpp
+++ b/include/boost/system/error_code.hpp
@@ -16,6 +16,7 @@
 #include <boost/system/detail/error_category.hpp>
 #include <boost/system/detail/generic_category.hpp>
 #include <boost/system/detail/system_category.hpp>
+#include <boost/system/detail/enable_if.hpp>
 #include <boost/system/api_config.hpp>
 #include <boost/system/detail/config.hpp>
 #include <boost/cstdint.hpp>
@@ -108,20 +109,9 @@ static const error_category & native_ecat BOOST_ATTRIBUTE_UNUSED = system_catego
 
 #endif
 
-// enable_if
-
 namespace detail
 {
 
-template<bool C, class T = void> struct enable_if
-{
-    typedef T type;
-};
-
-template<class T> struct enable_if<false, T>
-{
-};
-
 // failed_impl
 
 #if !defined(BOOST_SYSTEM_HAS_CONSTEXPR)