migrate std::invoke_result back to result_of

I'm trying to use a bit of code, below, that uses std::invoke_result on an old platform where it's not possible to use c++17, latest is c++11

using abc = std::chrono::system_clock;
using def = typename std::invoke_result<decltype(&abc::now)>::type;

any ideas on how to have equivalent code to compile with c++11? I've tried looking into result_of, without success yet.

thank you,

You can find a possible implementation here: https://en.cppreference.com/w/cpp/types/result_of. If I am not mistaken, it includes a C++11 conformant implementation.

However, outside of generic code, most uses are much simpler to replace. In your case it is

using abc = std::chrono::system_clock;
using def = decltype( std::declval<abc>().now() );

or simply

using def = std::chrono::time_point<std::chrono::system_clock>;

alternatively

using def = std::chrono::time_point< abc >;

I actually do not understand why invoke_result was used in the first place in your code. It is helpful in generic code or in general when you need to disambiguate different overloads with different return types. Neither is the case here, though that might be just due to a too simplistic example.