From 96cd1c0163d27064bb0b36c07f44d95888ed087d Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Tue, 15 Jun 2021 02:17:26 +0300
Subject: [PATCH] Add error_code comparisons against standard error code enums
 (to resolve the ambiguity when an enum is both standard and ours)

---
 include/boost/system/detail/error_code.hpp | 26 ++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/include/boost/system/detail/error_code.hpp b/include/boost/system/detail/error_code.hpp
index 776bcf4..b934a8d 100644
--- a/include/boost/system/detail/error_code.hpp
+++ b/include/boost/system/detail/error_code.hpp
@@ -390,6 +390,32 @@ public:
         return !( lhs == rhs );
     }
 
+    //
+
+    template<class E, class N1 = void, class N2 = typename detail::enable_if<std::is_error_code_enum<E>::value>::type>
+    inline friend bool operator==( error_code const & lhs, E rhs ) BOOST_NOEXCEPT
+    {
+        return lhs == make_error_code( rhs );
+    }
+
+    template<class E, class N1 = void, class N2 = typename detail::enable_if<std::is_error_code_enum<E>::value>::type>
+    inline friend bool operator==( E lhs, error_code const & rhs ) BOOST_NOEXCEPT
+    {
+        return make_error_code( lhs ) == rhs;
+    }
+
+    template<class E, class N1 = void, class N2 = typename detail::enable_if<std::is_error_code_enum<E>::value>::type>
+    inline friend bool operator!=( error_code const & lhs, E rhs ) BOOST_NOEXCEPT
+    {
+        return !( lhs == rhs );
+    }
+
+    template<class E, class N1 = void, class N2 = typename detail::enable_if<std::is_error_code_enum<E>::value>::type>
+    inline friend bool operator!=( E lhs, error_code const & rhs ) BOOST_NOEXCEPT
+    {
+        return !( lhs == rhs );
+    }
+
 #if defined(BOOST_SYSTEM_CLANG_6)
 
     inline friend bool operator==( error_code const & lhs, std::error_condition const & rhs ) BOOST_NOEXCEPT