C++20 removed std::result_of

215020267 commented 4 years ago

Description: In /std:c++17 mode, this triggers a deprecation warning in recent versions of MSVC. In /std:c++latest mode, now that microsoft/STL#380 has been merged, this will trigger an error in VS 2019 16.6 Preview 2.

Reproduce steps:

git clone --recursive https://github.com/Reactive-Extensions/RxCpp D:\RxCpp\src
cd D:\RxCpp\src
set CL=/D_SILENCE_CXX17_UNCAUGHT_EXCEPTION_DEPRECATION_WARNING /D_SILENCE_CXX17_ITERATOR_BASE_CLASS_DEPRECATION_WARNING
mkdir build_amd64
cd D:\RxCpp\src\build_amd64
cmake -G "Visual Studio 15 Win64" -DCMAKE_SYSTEM_VERSION=10.0.17134.0 ..\projects\CMake 2>&1
msbuild /m /p:Platform=x64 /p:Configuration=Debug RxCpp.sln /t:Rebuild /p:BuildInParallel=true 2>&1

ErrorMessage: F:\gitP\Reactive-Extensions\RxCpp\Rx\v2\src\rxcpp\rx-util.hpp(49): error C2039: 'result_of': is not a member of 'std' [F:\gitP\Reactive-Extensions\RxCpp\build_amd64\test\rxcpp_test_defer.vcxproj]

arolson101 commented 4 years ago

as a starting point, since result_of is available in versions <= 17, and invoke_result is available in versions >= 17, I did this:

// rx-util.hpp
#if _HAS_CXX17
template<class F, class... TN> using invoke_result_t = typename std::invoke_result<F, TN...>::type;
#else
template<class F, class... TN> using invoke_result_t = typename std::result_of<F(TN...)>::type;
#endif

...

template<typename T>
struct is_hashable<T,
    typename rxu::types_checked_from<
        typename filtered_hash<T>::result_type,
        typename filtered_hash<T>::argument_type,
        typename std::invoke_result<filtered_hash<T>, T>::type>::type>
    : std::true_type {};

then I changed all usages from rxu::result_of_t<A(B)> to rxu::invoke_result_t<A, B>

tcw165 commented 2 years ago

Do you know the steps to reproduce it on Mac? I'm looking into this issue but couldn't reproduce it.

amelonpie commented 11 months ago

Can this issue be closed since patch is merged?

ReactiveX / RxCpp

C++20 removed std::result_of #530