From 5470c5fa320fa492488db457d4846f00dfeb4d17 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Sun, 12 Feb 2023 19:25:39 +0200
Subject: [PATCH] Resolve C++20 issue with fn == bind(...). Fixes #45.

---
 include/boost/function.hpp                 |  2 ++
 include/boost/function/detail/epilogue.hpp | 39 ++++++++++++++++++++++
 2 files changed, 41 insertions(+)
 create mode 100644 include/boost/function/detail/epilogue.hpp

diff --git a/include/boost/function.hpp b/include/boost/function.hpp
index ef907e0..f6ee882 100644
--- a/include/boost/function.hpp
+++ b/include/boost/function.hpp
@@ -71,4 +71,6 @@
 #  undef BOOST_PP_ITERATION_PARAMS_1
 #endif
 
+#include <boost/function/detail/epilogue.hpp>
+
 #endif // !defined(BOOST_FUNCTION_MAX_ARGS_DEFINED) || (BOOST_FUNCTION_MAX_ARGS_DEFINED != BOOST_FUNCTION_MAX_ARGS)
diff --git a/include/boost/function/detail/epilogue.hpp b/include/boost/function/detail/epilogue.hpp
new file mode 100644
index 0000000..908788b
--- /dev/null
+++ b/include/boost/function/detail/epilogue.hpp
@@ -0,0 +1,39 @@
+// Boost.Function library
+
+#ifndef BOOST_FUNCTION_EPILOGUE_HPP
+#define BOOST_FUNCTION_EPILOGUE_HPP
+
+// Copyright 2023 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+// Resolve C++20 issue with fn == bind(...)
+// https://github.com/boostorg/function/issues/45
+
+#if !defined(BOOST_FUNCTION_NO_FUNCTION_TYPE_SYNTAX)
+
+namespace boost
+{
+
+namespace _bi
+{
+
+template<class R, class F, class L> class bind_t;
+
+} // namespace _bi
+
+template<class S, class R, class F, class L> bool operator==( function<S> const& f, _bi::bind_t<R, F, L> const& b )
+{
+    return f.contains( b );
+}
+
+template<class S, class R, class F, class L> bool operator!=( function<S> const& f, _bi::bind_t<R, F, L> const& b )
+{
+    return !f.contains( b );
+}
+
+} // namespace boost
+
+#endif // #if !defined(BOOST_FUNCTION_NO_FUNCTION_TYPE_SYNTAX)
+
+#endif // #ifndef BOOST_FUNCTION_EPILOGUE_HPP