Replaced std::result_of with std::invoke_result for c++17 or greater

CMakeLists.txt

@@ -114,6 +114,19 @@ if (NOT USE_CXX_EXCEPTIONS)
 	endif()
 endif()
 
+# /Zc:__cplusplus is required to make __cplusplus accurate
+# /Zc:__cplusplus is available starting with Visual Studio 2017 version 15.7
+# (according to https://docs.microsoft.com/en-us/cpp/build/reference/zc-cplusplus)
+# That version is equivalent to _MSC_VER==1914
+# (according to https://docs.microsoft.com/en-us/cpp/preprocessor/predefined-macros?view=vs-2019)
+# CMake's ${MSVC_VERSION} is equivalent to _MSC_VER
+# (according to https://cmake.org/cmake/help/latest/variable/MSVC_VERSION.html#variable:MSVC_VERSION)
+# GREATER and EQUAL are used because GREATER_EQUAL is available starting with CMake 3.7
+# (according to https://cmake.org/cmake/help/v3.7/release/3.7.html#commands)
+if ((MSVC) AND ((MSVC_VERSION GREATER 1914) OR (MSVC_VERSION EQUAL 1914)))
+    target_compile_options(Async++ PUBLIC /Zc:__cplusplus)
+endif()
+
 include(CMakePackageConfigHelpers)
 configure_package_config_file("${CMAKE_CURRENT_LIST_DIR}/Async++Config.cmake.in"
 	"${PROJECT_BINARY_DIR}/Async++Config.cmake"

include/async++/task.h

@@ -473,8 +473,14 @@ class local_task {
 };
 
 // Spawn a function asynchronously
+#if (__cplusplus >= 201703L)
+// Use std::invoke_result instead of std::result_of for C++17 or greater because std::result_of was deprecated in C++17 and removed in C++20
+template<typename Sched, typename Func>
+task<typename detail::remove_task<std::invoke_result_t<std::decay_t<Func>>>::type> spawn(Sched& sched, Func&& f)
+#else
 template<typename Sched, typename Func>
 task<typename detail::remove_task<typename std::result_of<typename std::decay<Func>::type()>::type>::type> spawn(Sched& sched, Func&& f)
+#endif
 {
 	// Using result_of in the function return type to work around bugs in the Intel
 	// C++ compiler.