io_result is annoying

[klemens-morgenstern]

The io_result type is rather annoying, because it doesn't bring me much but make it so I can't use any of the std::tuple functions, like:

• std::apply
• std::tie

I find it's an unnecessary complication that should just be a tuple.

[klemens-morgenstern]

apply uses std::get internally and we can't at overloads of std::get<> to std. Hence we cannot opt into those utilities.

I would just turn io_result into an alias:

template<typename ... Args>
using io_result = std::tuple<std::error_code, Args...>;