Move result_traits to its own header; add specializations for <functional> objects on MSVC >= C++17

include/boost/bind/bind.hpp

@@ -27,6 +27,7 @@
 #include <boost/type.hpp>
 #include <boost/is_placeholder.hpp>
 #include <boost/bind/arg.hpp>
+#include <boost/bind/detail/result_traits.hpp>
 #include <boost/detail/workaround.hpp>
 #include <boost/visit_each.hpp>
 #include <boost/core/enable_if.hpp>
@@ -59,29 +60,6 @@ template<class T> class weak_ptr;
 namespace _bi // implementation details
 {
 
-// result_traits
-
-template<class R, class F> struct result_traits
-{
-    typedef R type;
-};
-
-#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) && !defined(BOOST_NO_FUNCTION_TEMPLATE_ORDERING)
-
-struct unspecified {};
-
-template<class F> struct result_traits<unspecified, F>
-{
-    typedef typename F::result_type type;
-};
-
-template<class F> struct result_traits< unspecified, reference_wrapper<F> >
-{
-    typedef typename F::result_type type;
-};
-
-#endif
-
 // ref_compare
 
 template<class T> bool ref_compare( T const & a, T const & b, long )

include/boost/bind/detail/result_traits.hpp

@@ -0,0 +1,154 @@
+#ifndef BOOST_BIND_DETAIL_RESULT_TRAITS_HPP_INCLUDED
+#define BOOST_BIND_DETAIL_RESULT_TRAITS_HPP_INCLUDED
+
+// MS compatible compilers support #pragma once
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1020)
+# pragma once
+#endif
+
+//
+//  bind/detail/result_traits.hpp
+//
+//  boost/bind.hpp support header, return type deduction
+//
+//  Copyright 2006, 2020 Peter Dimov
+//
+//  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/bind/bind.html for documentation.
+//
+
+#if defined(_MSVC_LANG) && _MSVC_LANG >= 17
+#include <functional>
+#endif
+
+namespace boost
+{
+
+namespace _bi
+{
+
+template<class R, class F> struct result_traits
+{
+    typedef R type;
+};
+
+struct unspecified {};
+
+template<class F> struct result_traits<unspecified, F>
+{
+    typedef typename F::result_type type;
+};
+
+template<class F> struct result_traits< unspecified, reference_wrapper<F> >
+{
+    typedef typename F::result_type type;
+};
+
+#if defined(_MSVC_LANG) && _MSVC_LANG >= 17
+
+template<class T> struct result_traits< unspecified, std::plus<T> >
+{
+    typedef T type;
+};
+
+template<class T> struct result_traits< unspecified, std::minus<T> >
+{
+    typedef T type;
+};
+
+template<class T> struct result_traits< unspecified, std::multiplies<T> >
+{
+    typedef T type;
+};
+
+template<class T> struct result_traits< unspecified, std::divides<T> >
+{
+    typedef T type;
+};
+
+template<class T> struct result_traits< unspecified, std::modulus<T> >
+{
+    typedef T type;
+};
+
+template<class T> struct result_traits< unspecified, std::negate<T> >
+{
+    typedef T type;
+};
+
+template<class T> struct result_traits< unspecified, std::equal_to<T> >
+{
+    typedef bool type;
+};
+
+template<class T> struct result_traits< unspecified, std::not_equal_to<T> >
+{
+    typedef bool type;
+};
+
+template<class T> struct result_traits< unspecified, std::greater<T> >
+{
+    typedef bool type;
+};
+
+template<class T> struct result_traits< unspecified, std::less<T> >
+{
+    typedef bool type;
+};
+
+template<class T> struct result_traits< unspecified, std::greater_equal<T> >
+{
+    typedef bool type;
+};
+
+template<class T> struct result_traits< unspecified, std::less_equal<T> >
+{
+    typedef bool type;
+};
+
+template<class T> struct result_traits< unspecified, std::logical_and<T> >
+{
+    typedef bool type;
+};
+
+template<class T> struct result_traits< unspecified, std::logical_or<T> >
+{
+    typedef bool type;
+};
+
+template<class T> struct result_traits< unspecified, std::logical_not<T> >
+{
+    typedef bool type;
+};
+
+template<class T> struct result_traits< unspecified, std::bit_and<T> >
+{
+    typedef T type;
+};
+
+template<class T> struct result_traits< unspecified, std::bit_or<T> >
+{
+    typedef T type;
+};
+
+template<class T> struct result_traits< unspecified, std::bit_xor<T> >
+{
+    typedef T type;
+};
+
+template<class T> struct result_traits< unspecified, std::bit_not<T> >
+{
+    typedef T type;
+};
+
+#endif
+
+} // namespace _bi
+
+} // namespace boost
+
+#endif // #ifndef BOOST_BIND_DETAIL_RESULT_TRAITS_HPP_INCLUDED