Niall Douglas wrote:
See what you make of my toy std::variant<> based Outcome at:
FWIW, Niall, I convinced my variant implementation to work in Compiler Explorer:
so you can try it for a spin. It's never-valueless, ever, so you can dispense with the "safe assign" workarounds.
Here's a simplistic result<> based on that: https://godbolt.org/g/EG6Kht g++ 7.1 turns this: #include <iostream> result<int> function() { return 14; } int main() { std::cout << function().value() << std::endl; } into this: function(): mov rax, rdi mov DWORD PTR [rdi], 1 mov DWORD PTR [rdi+8], 14 ret main: sub rsp, 8 mov esi, 14 mov edi, OFFSET FLAT:std::cout call std::basic_ostream<char, std::char_traits<char>
::operator<<(int) mov rdi, rax call std::basic_ostream<char, std::char_traits<char> >& std::endl<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&) xor eax, eax add rsp, 8 ret _GLOBAL__sub_I__Z8functionv: sub rsp, 8 mov edi, OFFSET FLAT:std::__ioinit call std::ios_base::Init::Init() mov edx, OFFSET FLAT:__dso_handle mov esi, OFFSET FLAT:std::__ioinit mov edi, OFFSET FLAT:std::ios_base::Init::~Init() add rsp, 8 jmp __cxa_atexit