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//! Definition of the Ok combinator, a successful value that's immediately //! ready. use core::marker; use {Future, Poll, Async}; /// A future representing a finished successful computation. /// /// Created by the `finished` function. #[must_use = "futures do nothing unless polled"] pub struct Ok<T, E> { t: Option<T>, _e: marker::PhantomData<E>, } /// Creates a "leaf future" from an immediate value of a finished and /// successful computation. /// /// The returned future is similar to `done` where it will immediately run a /// scheduled callback with the provided value. /// /// # Examples /// /// ``` /// use futures::future::*; /// /// let future_of_1 = ok::<u32, u32>(1); /// ``` pub fn ok<T, E>(t: T) -> Ok<T, E> { Ok { t: Some(t), _e: marker::PhantomData } } impl<T, E> Future for Ok<T, E> { type Item = T; type Error = E; fn poll(&mut self) -> Poll<T, E> { Ok(Async::Ready(self.t.take().expect("cannot poll Ok twice"))) } }