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use crate::stream::{Fuse, Stream};
use core::pin::Pin;
use core::task::{Context, Poll};
use pin_project_lite::pin_project;
pin_project! {
/// Stream returned by the [`chain`](super::StreamExt::chain) method.
pub struct Chain<T, U> {
#[pin]
a: Fuse<T>,
#[pin]
b: U,
}
}
impl<T, U> Chain<T, U> {
pub(super) fn new(a: T, b: U) -> Chain<T, U>
where
T: Stream,
U: Stream,
{
Chain { a: Fuse::new(a), b }
}
}
impl<T, U> Stream for Chain<T, U>
where
T: Stream,
U: Stream<Item = T::Item>,
{
type Item = T::Item;
fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<T::Item>> {
use Poll::Ready;
let me = self.project();
if let Some(v) = ready!(me.a.poll_next(cx)) {
return Ready(Some(v));
}
me.b.poll_next(cx)
}
fn size_hint(&self) -> (usize, Option<usize>) {
super::merge_size_hints(self.a.size_hint(), self.b.size_hint())
}
}
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