Rust's for-loop construct probably changed

Having read that article (and the sequel), there's one thing that bugs me a little about the tack Rust took. Rust *already* uses message-passing concurrency, and that allows a simple transformation from internal to external iterators by creating a stream, passing the chan into a task that runs the internal iterator (whose block closes over the chan), and then return or wrap an iterator for the port. So it startles me a bit that there isn't an Iterator implementation that does the transformation, yielding the best of both worlds.