46 lines
1009 B
Rust
46 lines
1009 B
Rust
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use super::assert_stream;
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use core::marker::PhantomData;
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use core::pin::Pin;
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use futures_core::stream::{FusedStream, Stream};
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use futures_core::task::{Context, Poll};
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/// Stream for the [`empty`] function.
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#[derive(Debug)]
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#[must_use = "streams do nothing unless polled"]
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pub struct Empty<T> {
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_phantom: PhantomData<T>,
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}
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/// Creates a stream which contains no elements.
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///
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/// The returned stream will always return `Ready(None)` when polled.
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pub fn empty<T>() -> Empty<T> {
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assert_stream::<T, _>(Empty { _phantom: PhantomData })
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}
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impl<T> Unpin for Empty<T> {}
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impl<T> FusedStream for Empty<T> {
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fn is_terminated(&self) -> bool {
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true
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}
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}
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impl<T> Stream for Empty<T> {
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type Item = T;
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fn poll_next(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Option<Self::Item>> {
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Poll::Ready(None)
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}
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fn size_hint(&self) -> (usize, Option<usize>) {
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(0, Some(0))
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}
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}
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impl<T> Clone for Empty<T> {
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fn clone(&self) -> Self {
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empty()
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}
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}
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