I think the closest you can get is something like: class odd {...}; class even {...}; std::variant<odd, even> p(int a) { if (a&1) return o

I think the closest you can get is something like: class odd {...}; class even {...}; std::variant<odd, even> p(int a) { if (a&1) return odd{a}; else return even{a}; } Now which of `even` or `odd` you get is based on the value of `a`.