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diff --git a/boost/callable_traits/detail/utility.hpp b/boost/callable_traits/detail/utility.hpp
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+++ b/boost/callable_traits/detail/utility.hpp
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+/*
+
+@Copyright Barrett Adair 2015-2017
+Distributed under the Boost Software License, Version 1.0.
+(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
+
+*/
+
+#ifndef BOOST_CLBL_TRTS_DETAIL_UTILITY_HPP
+#define BOOST_CLBL_TRTS_DETAIL_UTILITY_HPP
+
+#include <boost/callable_traits/detail/config.hpp>
+#include <boost/callable_traits/detail/sfinae_errors.hpp>
+#include <boost/callable_traits/detail/qualifier_flags.hpp>
+
+namespace boost { namespace callable_traits { namespace detail {
+
+struct cdecl_tag{};
+struct stdcall_tag{};
+struct fastcall_tag{};
+struct pascal_tag{};
+
+struct invalid_type { invalid_type() = delete; };
+struct reference_error { reference_error() = delete; };
+
+template<typename T>
+using error_type = typename std::conditional<
+    std::is_reference<T>::value, reference_error, invalid_type>::type;
+
+#ifdef BOOST_CLBL_TRTS_DISABLE_ABOMINABLE_FUNCTIONS
+struct abominable_functions_not_supported_on_this_compiler{};
+#endif
+
+// used to convey "this type doesn't matter" in code
+struct dummy {};
+
+// used as return type in failed SFINAE tests
+struct substitution_failure : std::false_type{};
+
+template<bool Value>
+using bool_type = std::integral_constant<bool, Value>;
+
+// shorthand for std::tuple_element
+template<std::size_t I, typename Tup>
+using at = typename std::tuple_element<I, Tup>::type;
+
+template<typename T, typename Class>
+using add_member_pointer = T Class::*;
+
+template<typename L, typename R, typename ErrorType>
+ using fail_when_same = fail_if<std::is_same<L, R>::value, ErrorType>;
+
+template<typename T, typename ErrorType,
+    typename U = typename std::remove_reference<T>::type>
+using try_but_fail_if_invalid = sfinae_try<T,
+    fail_when_same<U, invalid_type, ErrorType>,
+    fail_when_same<U, reference_error,
+        reference_type_not_supported_by_this_metafunction>>;
+
+template<typename T, typename ErrorType,
+    typename U = typename std::remove_reference<T>::type,
+    bool is_reference_error = std::is_same<reference_error, U>::value>
+using fail_if_invalid = fail_if<
+    std::is_same<U, invalid_type>::value || is_reference_error,
+    typename std::conditional<is_reference_error,
+        reference_type_not_supported_by_this_metafunction, ErrorType>::type>;
+
+template<typename T, typename Fallback>
+using fallback_if_invalid = typename std::conditional<
+    std::is_same<T, invalid_type>::value, Fallback, T>::type;
+
+template<typename T, template<class> class Alias, typename U = Alias<T>>
+struct force_sfinae {
+    using type = U;
+};
+
+template<typename T>
+using shallow_decay = typename std::remove_cv<
+    typename std::remove_reference<T>::type>::type;
+
+template<typename T>
+struct is_reference_wrapper_t {
+    using type = std::false_type;
+};
+
+template<typename T>
+struct is_reference_wrapper_t<std::reference_wrapper<T>> {
+    using type = std::true_type;
+};
+
+template<typename T>
+using is_reference_wrapper =
+    typename is_reference_wrapper_t<shallow_decay<T>>::type;
+
+template<typename T, typename = std::true_type>
+struct unwrap_reference_t {
+    using type = T;
+};
+
+template<typename T>
+struct unwrap_reference_t<T, is_reference_wrapper<T>> {
+    using type = decltype(std::declval<T>().get());
+};
+
+// removes std::reference_wrapper
+template<typename T>
+using unwrap_reference = typename unwrap_reference_t<T>::type;
+
+}}} // namespace boost::callable_traits::detail
+
+#endif // #ifndef BOOST_CLBL_TRTS_DETAIL_UTILITY_HPP