| use core::marker::{Unpin, PhantomData}; |
| use core::pin::Pin; |
| use futures_core::stream::Stream; |
| use futures_core::task::{LocalWaker, Poll}; |
| |
| /// A stream which contains no elements. |
| /// |
| /// This stream can be created with the `stream::empty` function. |
| #[derive(Debug)] |
| #[must_use = "streams do nothing unless polled"] |
| pub struct Empty<T> { |
| _phantom: PhantomData<T> |
| } |
| |
| /// Creates a stream which contains no elements. |
| /// |
| /// The returned stream will always return `Ready(None)` when polled. |
| pub fn empty<T>() -> Empty<T> { |
| Empty { |
| _phantom: PhantomData |
| } |
| } |
| |
| impl<T> Unpin for Empty<T> {} |
| |
| impl<T> Stream for Empty<T> { |
| type Item = T; |
| |
| fn poll_next(self: Pin<&mut Self>, _: &LocalWaker) -> Poll<Option<Self::Item>> { |
| Poll::Ready(None) |
| } |
| } |