From 3e2f0199cf4ae6343bcda40ffa3ae06335626615 Mon Sep 17 00:00:00 2001
From: Nikita Kniazev <nok.raven@gmail.com>
Date: Mon, 8 Mar 2021 01:28:05 +0300
Subject: [PATCH] Use variadic templates in result_of

---
 .../utility/detail/result_of_variadic.hpp     | 190 ++++++++++++++++++
 include/boost/utility/result_of.hpp           |  29 ++-
 2 files changed, 210 insertions(+), 9 deletions(-)
 create mode 100644 include/boost/utility/detail/result_of_variadic.hpp

diff --git a/include/boost/utility/detail/result_of_variadic.hpp b/include/boost/utility/detail/result_of_variadic.hpp
new file mode 100644
index 0000000..f6929f8
--- /dev/null
+++ b/include/boost/utility/detail/result_of_variadic.hpp
@@ -0,0 +1,190 @@
+// Boost result_of library
+
+//  Copyright Douglas Gregor 2004. Use, modification and
+//  distribution is subject to 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)
+
+//  Copyright Daniel Walker, Eric Niebler, Michel Morin 2008-2012.
+//  Use, modification and distribution is subject to 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)
+
+// For more information, see http://www.boost.org/libs/utility
+
+#ifndef BOOST_RESULT_OF_HPP
+# error Boost result_of - do not include this file!
+#endif
+
+template<typename F, typename... Args>
+struct tr1_result_of<F(Args...)>
+    : conditional<
+        is_pointer<F>::value || is_member_function_pointer<F>::value
+        , boost::detail::tr1_result_of_impl<
+            typename remove_cv<F>::type,
+            typename remove_cv<F>::type(Args...),
+            (boost::detail::result_of_has_result_type<F>::value)>
+        , boost::detail::tr1_result_of_impl<
+            F,
+            F(Args...),
+            (boost::detail::result_of_has_result_type<F>::value)> >::type { };
+
+#ifdef BOOST_RESULT_OF_USE_DECLTYPE
+template<typename F, typename... Args>
+struct result_of<F(Args...)>
+    : detail::cpp0x_result_of<F(Args...)> { };
+#endif // BOOST_RESULT_OF_USE_DECLTYPE
+
+#ifdef BOOST_RESULT_OF_USE_TR1_WITH_DECLTYPE_FALLBACK
+template<typename F, typename... Args>
+struct result_of<F(Args...)>
+    : conditional<detail::result_of_has_result_type<F>::value || detail::result_of_has_result<F>::value,
+               tr1_result_of<F(Args...)>,
+               detail::cpp0x_result_of<F(Args...)> >::type { };
+#endif // BOOST_RESULT_OF_USE_TR1_WITH_DECLTYPE_FALLBACK
+
+#if defined(BOOST_RESULT_OF_USE_DECLTYPE) || defined(BOOST_RESULT_OF_USE_TR1_WITH_DECLTYPE_FALLBACK)
+
+namespace detail {
+
+template<typename F, typename... Args>
+struct cpp0x_result_of<F(Args...)>
+    : conditional<
+          is_member_function_pointer<F>::value
+        , detail::tr1_result_of_impl<
+            typename remove_cv<F>::type,
+            typename remove_cv<F>::type(Args...), false
+          >
+        , detail::cpp0x_result_of_impl<
+              F(Args...)
+          >
+      >::type
+{};
+
+#ifdef BOOST_NO_SFINAE_EXPR
+
+template<typename F>
+struct result_of_callable_fun_2;
+
+template<typename R, typename... Args>
+struct result_of_callable_fun_2<R(Args...)> {
+    R operator()(Args...) const;
+    typedef result_of_private_type const &(*pfn_t)(...);
+    operator pfn_t() const volatile;
+};
+
+template<typename F>
+struct result_of_callable_fun
+  : result_of_callable_fun_2<F>
+{};
+
+template<typename F>
+struct result_of_callable_fun<F *>
+  : result_of_callable_fun_2<F>
+{};
+
+template<typename F>
+struct result_of_select_call_wrapper_type
+  : conditional<
+        is_class<typename remove_reference<F>::type>::value,
+        result_of_wrap_callable_class<F>,
+        type_identity<result_of_callable_fun<typename remove_cv<typename remove_reference<F>::type>::type> >
+    >::type
+{};
+
+template<typename F, typename... Args>
+struct result_of_is_callable {
+    typedef typename result_of_select_call_wrapper_type<F>::type wrapper_t;
+    static const bool value = (
+        sizeof(result_of_no_type) == sizeof(detail::result_of_is_private_type(
+            (boost::declval<wrapper_t>()(boost::declval<Args>()...), result_of_weird_type())
+        ))
+    );
+    typedef integral_constant<bool, value> type;
+};
+
+template<typename F, typename... Args>
+struct cpp0x_result_of_impl<F(Args...), true>
+    : lazy_enable_if<
+          result_of_is_callable<F, Args...>
+        , cpp0x_result_of_impl<F(Args...), false>
+      >
+{};
+
+template<typename F, typename... Args>
+struct cpp0x_result_of_impl<F(Args...), false>
+{
+  typedef decltype(
+    boost::declval<F>()(
+      boost::declval<Args>()...
+    )
+  ) type;
+};
+
+#else // BOOST_NO_SFINAE_EXPR
+
+template<typename F, typename... Args>
+struct cpp0x_result_of_impl<F(Args...),
+                            typename result_of_always_void<decltype(
+                                boost::declval<F>()(
+                                    boost::declval<Args>()...
+                                )
+                            )>::type> {
+  typedef decltype(
+    boost::declval<F>()(
+      boost::declval<Args>()...
+    )
+  ) type;
+};
+
+#endif // BOOST_NO_SFINAE_EXPR
+
+} // namespace detail
+
+#else // defined(BOOST_RESULT_OF_USE_DECLTYPE) || defined(BOOST_RESULT_OF_USE_TR1_WITH_DECLTYPE_FALLBACK)
+
+template<typename F, typename... Args>
+struct result_of<F(Args...)>
+    : tr1_result_of<F(Args...)> { };
+
+#endif // defined(BOOST_RESULT_OF_USE_DECLTYPE)
+
+namespace detail {
+
+template<typename R, typename FArgs, typename... Args>
+struct tr1_result_of_impl<R (*)(Args...), FArgs, false>
+{
+  typedef R type;
+};
+
+template<typename R, typename FArgs, typename... Args>
+struct tr1_result_of_impl<R (&)(Args...), FArgs, false>
+{
+  typedef R type;
+};
+
+template<typename R, typename FArgs, typename C, typename... Args>
+struct tr1_result_of_impl<R (C::*)(Args...), FArgs, false>
+{
+  typedef R type;
+};
+
+template<typename R, typename FArgs, typename C, typename... Args>
+struct tr1_result_of_impl<R (C::*)(Args...) const, FArgs, false>
+{
+  typedef R type;
+};
+
+template<typename R, typename FArgs, typename C, typename... Args>
+struct tr1_result_of_impl<R (C::*)(Args...) volatile, FArgs, false>
+{
+  typedef R type;
+};
+
+template<typename R, typename FArgs, typename C, typename... Args>
+struct tr1_result_of_impl<R (C::*)(Args...) const volatile, FArgs, false>
+{
+  typedef R type;
+};
+
+}
diff --git a/include/boost/utility/result_of.hpp b/include/boost/utility/result_of.hpp
index 2b652ba..9d444f9 100644
--- a/include/boost/utility/result_of.hpp
+++ b/include/boost/utility/result_of.hpp
@@ -10,13 +10,6 @@
 #define BOOST_RESULT_OF_HPP
 
 #include <boost/config.hpp>
-#include <boost/preprocessor/cat.hpp>
-#include <boost/preprocessor/iteration/iterate.hpp>
-#include <boost/preprocessor/repetition/enum_params.hpp>
-#include <boost/preprocessor/repetition/enum_trailing_params.hpp>
-#include <boost/preprocessor/repetition/enum_binary_params.hpp>
-#include <boost/preprocessor/repetition/enum_shifted_params.hpp>
-#include <boost/preprocessor/facilities/intercept.hpp>
 #include <boost/detail/workaround.hpp>
 #include <boost/type_traits/is_class.hpp>
 #include <boost/type_traits/is_pointer.hpp>
@@ -29,6 +22,20 @@
 #include <boost/type_traits/integral_constant.hpp>
 #include <boost/core/enable_if.hpp>
 
+#ifdef BOOST_NO_CXX11_VARIADIC_TEMPLATES
+#  undef BOOST_RESULT_OF_NO_VARIADIC_TEMPLATES
+#  define BOOST_RESULT_OF_NO_VARIADIC_TEMPLATES
+#endif
+#ifdef BOOST_RESULT_OF_NO_VARIADIC_TEMPLATES
+#  include <boost/preprocessor/cat.hpp>
+#  include <boost/preprocessor/iteration/iterate.hpp>
+#  include <boost/preprocessor/repetition/enum_params.hpp>
+#  include <boost/preprocessor/repetition/enum_trailing_params.hpp>
+#  include <boost/preprocessor/repetition/enum_binary_params.hpp>
+#  include <boost/preprocessor/repetition/enum_shifted_params.hpp>
+#  include <boost/preprocessor/facilities/intercept.hpp>
+#endif
+
 #ifndef BOOST_RESULT_OF_NUM_ARGS
 #  define BOOST_RESULT_OF_NUM_ARGS 16
 #endif
@@ -217,8 +224,12 @@ struct tr1_result_of_impl<F, FArgs, false>
 
 } // end namespace detail
 
-#define BOOST_PP_ITERATION_PARAMS_1 (3,(0,BOOST_RESULT_OF_NUM_ARGS,<boost/utility/detail/result_of_iterate.hpp>))
-#include BOOST_PP_ITERATE()
+#ifndef BOOST_RESULT_OF_NO_VARIADIC_TEMPLATES
+#  include <boost/utility/detail/result_of_variadic.hpp>
+#else
+#  define BOOST_PP_ITERATION_PARAMS_1 (3,(0,BOOST_RESULT_OF_NUM_ARGS,<boost/utility/detail/result_of_iterate.hpp>))
+#  include BOOST_PP_ITERATE()
+#endif
 
 #if 0
 // inform dependency trackers, as they can't see through macro includes