use core::marker; use core::pin::Pin; use futures_core::future::{FusedFuture, Future}; use futures_core::task::{Context, Poll}; /// Future for the [`pending()`] function. #[derive(Debug)] #[must_use = "futures do nothing unless you `.await` or poll them"] pub struct Pending<T> { _data: marker::PhantomData<T>, } impl<T> FusedFuture for Pending<T> { fn is_terminated(&self) -> bool { true } } /// Creates a future which never resolves, representing a computation that never /// finishes. /// /// The returned future will forever return [`Poll::Pending`]. /// /// # Examples /// /// ```ignore /// # futures::executor::block_on(async { /// use futures::future; /// /// let future = future::pending(); /// let () = future.await; /// unreachable!(); /// # }); /// ``` pub fn pending<T>() -> Pending<T> { Pending { _data: marker::PhantomData, } } impl<T> Future for Pending<T> { type Output = T; fn poll(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<T> { Poll::Pending } } impl<T> Unpin for Pending<T> { } impl<T> Clone for Pending<T> { fn clone(&self) -> Self { pending() } }