coro::generator is not compatible with std::ranges::elements_of

[Tearnote]

C++23 introduced std::ranges::elements_of, which allows for generating elements of generators with less overhead. A good example is on the std::generator cppreference page: https://en.cppreference.com/w/cpp/coroutine/generator.html

When available, it works with std::generator, but not coro::generator. I don't fully understand what is required for compatibility, but it seems to be a specific overload of yield_value(). elements_of itself is just five lines: https://github.com/anonymouspc/llvm/blob/main/libcxx/include/__ranges/elements_of.h#L32

Is this something that libcoro can implement?

[jbaldwin]

If I'm understanding std::ranges::elements_of(r) correctly it is basically a generator inside a generator.

Given the following code:

std::generator<T> gen(std::ranges::input_range auto&& r)
{
    co_yield std::ranges::elements_of(r); // yield each element of r
}

it could be written also as:

std::generator<T> gen(std::ranges::input_range auto&& r)
{
    for (auto&& i : r)
    {
        co_yield i;
    }
}