blob: 4ea12f4586e6c205fc83b568529d9b66a6212a63 [file] [log] [blame]
use {Future, Poll, Async};
/// Future for the `map_err` combinator, changing the error type of a future.
///
/// This is created by the `Future::map_err` method.
#[derive(Debug)]
#[must_use = "futures do nothing unless polled"]
pub struct MapErr<A, F> where A: Future {
future: A,
f: Option<F>,
}
pub fn new<A, F>(future: A, f: F) -> MapErr<A, F>
where A: Future
{
MapErr {
future: future,
f: Some(f),
}
}
impl<U, A, F> Future for MapErr<A, F>
where A: Future,
F: FnOnce(A::Error) -> U,
{
type Item = A::Item;
type Error = U;
fn poll(&mut self) -> Poll<A::Item, U> {
let e = match self.future.poll() {
Ok(Async::NotReady) => return Ok(Async::NotReady),
other => other,
};
e.map_err(self.f.take().expect("cannot poll MapErr twice"))
}
}