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diff --git a/boost/multi_index/detail/is_function.hpp b/boost/multi_index/detail/is_function.hpp
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+++ b/boost/multi_index/detail/is_function.hpp
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+/* Copyright 2003-2019 Joaquin M Lopez Munoz.
+ * 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 http://www.boost.org/libs/multi_index for library home page.
+ */
+
+#ifndef BOOST_MULTI_INDEX_DETAIL_IS_FUNCTION_HPP
+#define BOOST_MULTI_INDEX_DETAIL_IS_FUNCTION_HPP
+
+#if defined(_MSC_VER)
+#pragma once
+#endif
+
+#include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
+#include <boost/detail/workaround.hpp>
+
+#if !defined(BOOST_NO_CXX11_HDR_TYPE_TRAITS)||\
+    BOOST_WORKAROUND(_LIBCPP_VERSION,<30700)||\
+    BOOST_WORKAROUND(BOOST_LIBSTDCXX_VERSION,<40802)
+/* libc++: std::is_function<void() const> fails,
+ * https://bugs.llvm.org/show_bug.cgi?id=20084
+ *
+ * libstdc++-v3: std::is_function does not support ref-qualified function types,
+ * https://github.com/gcc-mirror/gcc/commit/
+ *   2fa630fb50ba29d8e891c52a75aaec261b07874e#
+ *   diff-6547f965a8d66bf35a6388fcf404aaa3
+ */
+
+#include <boost/type_traits/is_function.hpp>
+
+namespace boost{namespace multi_index{namespace detail{
+
+template<typename T>
+struct is_function:boost::is_function<T>{};
+
+}}} /* namespace boost::multi_index::detail */
+
+#else
+
+#include <type_traits>
+
+namespace boost{namespace multi_index{namespace detail{
+
+template<typename T>
+struct is_function:std::is_function<T>{};
+
+}}} /* namespace boost::multi_index::detail */
+
+#endif
+#endif