blob: 1b204d376aeefc96279edae9b07fbf94e8e0da81 [file] [log] [blame]
//! Definition of the `Option` (optional step) combinator
use {Future, Poll, Async};
impl<F, T, E> Future for Option<F> where F: Future<Item=T, Error=E> {
type Item = Option<T>;
type Error = E;
fn poll(&mut self) -> Poll<Option<T>, E> {
match *self {
None => Ok(Async::Ready(None)),
Some(ref mut x) => x.poll().map(|x| x.map(Some)),
}
}
}