What is FutureVar used for? We're considering its future in chronos and haven't found much practical use for it - getting rid of it would simplify things.
I imagine that perhaps it's used for var parameters of async functions as an alternate way of returning things, but it's not entire clear - does anyone actually use it, and why?
It's used to work around the limitation that closure iterators have, which is that var T cannot be used in arguments.
Ideally we would transform var T in arguments to a FutureVar (or fix support in the compiler).