Sure, I'm not informed enough to make suggestions here :)

Are we safe from the user calling on_next with a const rvalue directly?

Thanks!

Yes, one of the weird parts of perfect-forwarding in C++ is that since the Value&& v parameter is named, it is not an R-Value which is why std::forward must be used to recover the original type.

This means that this use of as_const in on_next will not ever be passed an R-Value.

@elel, thank you for the help in getting this done.