blob: bfe286975c4585bd05e181bd590b7d85227c4345 [file] [log] [blame]
use {Future, IntoFuture, Poll};
use core::fmt;
use super::chain::Chain;
/// Future for the `flatten` combinator, flattening a future-of-a-future to get just
/// the result of the final future.
///
/// This is created by the `Future::flatten` method.
#[must_use = "futures do nothing unless polled"]
pub struct Flatten<A> where A: Future, A::Item: IntoFuture {
state: Chain<A, <A::Item as IntoFuture>::Future, ()>,
}
impl<A> fmt::Debug for Flatten<A>
where A: Future + fmt::Debug,
A::Item: IntoFuture,
<<A as IntoFuture>::Item as IntoFuture>::Future: fmt::Debug,
{
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
fmt.debug_struct("Flatten")
.field("state", &self.state)
.finish()
}
}
pub fn new<A>(future: A) -> Flatten<A>
where A: Future,
A::Item: IntoFuture,
{
Flatten {
state: Chain::new(future, ()),
}
}
impl<A> Future for Flatten<A>
where A: Future,
A::Item: IntoFuture,
<<A as Future>::Item as IntoFuture>::Error: From<<A as Future>::Error>
{
type Item = <<A as Future>::Item as IntoFuture>::Item;
type Error = <<A as Future>::Item as IntoFuture>::Error;
fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
self.state.poll(|a, ()| {
let future = a?.into_future();
Ok(Err(future))
})
}
}