void f(int, float);
double bar(int, float);

// type ReturnType<T extends (...args: any) => any> = T extends (...args: any) => infer R ? R : any;

struct never {};

template<typename T> struct return_type_impl {
 using type = never;
};

template<typename ret, typename ... args> struct return_type_impl<ret(args...)> {
 using type = ret;
};


template<typename T> using return_type = typename return_type_impl<T>::type;

static_assert(__is_same(return_type<decltype(f)>, void));
static_assert(__is_same(return_type<decltype(bar)>, double));
static_assert(__is_same(return_type<int>, never));

auto model = [=](auto model_name) {
   return map[model_name].create();
 };
это на тайплевеле чтоли работает?

I’m writing this article to talk about the proof and programming language I developed, Formality, some bits of its history, why it exists…