64 lines
1.6 KiB
Rust
64 lines
1.6 KiB
Rust
use crate::fmt::{self, Debug};
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use crate::future::Future;
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use crate::marker;
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use crate::pin::Pin;
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use crate::task::{Context, Poll};
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/// Creates a future which never resolves, representing a computation that never
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/// finishes.
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///
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/// This `struct` is created by the [`pending`] function. See its
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/// documentation for more.
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///
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/// [`pending`]: fn.pending.html
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#[stable(feature = "future_readiness_fns", since = "1.48.0")]
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#[must_use = "futures do nothing unless you `.await` or poll them"]
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pub struct Pending<T> {
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_data: marker::PhantomData<T>,
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}
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/// Creates a future which never resolves, representing a computation that never
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/// finishes.
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///
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/// # Examples
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///
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/// ```no_run
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/// use core::future;
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///
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/// # async fn run() {
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/// let future = future::pending();
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/// let () = future.await;
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/// unreachable!();
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/// # }
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/// ```
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#[stable(feature = "future_readiness_fns", since = "1.48.0")]
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pub fn pending<T>() -> Pending<T> {
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Pending { _data: marker::PhantomData }
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}
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#[stable(feature = "future_readiness_fns", since = "1.48.0")]
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impl<T> Future for Pending<T> {
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type Output = T;
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fn poll(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<T> {
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Poll::Pending
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}
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}
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#[stable(feature = "future_readiness_fns", since = "1.48.0")]
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impl<T> Unpin for Pending<T> {}
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#[stable(feature = "future_readiness_fns", since = "1.48.0")]
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impl<T> Debug for Pending<T> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.debug_struct("Pending").finish()
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}
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}
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#[stable(feature = "future_readiness_fns", since = "1.48.0")]
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impl<T> Clone for Pending<T> {
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fn clone(&self) -> Self {
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pending()
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}
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}
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