Trait futures::prelude::stream::Stream

#[must_use = "streams do nothing unless polled"]pub trait Stream {
    type Item;
    pub fn poll_next(
        self: Pin<&mut Self>, 
        cx: &mut Context<'_>
    ) -> Poll<Option<Self::Item>>;

    pub fn size_hint(&self) -> (usize, Option<usize>) { ... }
}

A stream of values produced asynchronously.

If Future<Output = T> is an asynchronous version of T, then Stream<Item = T> is an asynchronous version of Iterator<Item = T>. A stream represents a sequence of value-producing events that occur asynchronously to the caller.

The trait is modeled after Future, but allows poll_next to be called even after a value has been produced, yielding None once the stream has been fully exhausted.

Associated Types

type Item

Values yielded by the stream.

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Required methods

pub fn poll_next(
    self: Pin<&mut Self>,
    cx: &mut Context<'_>
) -> Poll<Option<Self::Item>>

Attempt to pull out the next value of this stream, registering the current task for wakeup if the value is not yet available, and returning None if the stream is exhausted.

Return value

There are several possible return values, each indicating a distinct stream state:

• Poll::Pending means that this stream’s next value is not ready yet. Implementations will ensure that the current task will be notified when the next value may be ready.

• Poll::Ready(Some(val)) means that the stream has successfully produced a value, val, and may produce further values on subsequent poll_next calls.

• Poll::Ready(None) means that the stream has terminated, and poll_next should not be invoked again.

Panics

Once a stream has finished (returned Ready(None) from poll_next), calling its poll_next method again may panic, block forever, or cause other kinds of problems; the Stream trait places no requirements on the effects of such a call. However, as the poll_next method is not marked unsafe, Rust’s usual rules apply: calls must never cause undefined behavior (memory corruption, incorrect use of unsafe functions, or the like), regardless of the stream’s state.

If this is difficult to guard against then the fuse adapter can be used to ensure that poll_next always returns Ready(None) in subsequent calls.

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Provided methods

pub fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the stream.

Specifically, size_hint() returns a tuple where the first element is the lower bound, and the second element is the upper bound.

The second half of the tuple that is returned is an Option<usize>. A None here means that either there is no known upper bound, or the upper bound is larger than usize.

Implementation notes

It is not enforced that a stream implementation yields the declared number of elements. A buggy stream may yield less than the lower bound or more than the upper bound of elements.

size_hint() is primarily intended to be used for optimizations such as reserving space for the elements of the stream, but must not be trusted to e.g., omit bounds checks in unsafe code. An incorrect implementation of size_hint() should not lead to memory safety violations.

That said, the implementation should provide a correct estimation, because otherwise it would be a violation of the trait’s protocol.

The default implementation returns (0, None) which is correct for any stream.

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Implementations on Foreign Types

impl<'_, S> Stream for &'_ mut S where
    S: Stream + Unpin + ?Sized, 

type Item = <S as Stream>::Item

pub fn poll_next(
    self: Pin<&mut &'_ mut S>,
    cx: &mut Context<'_>
) -> Poll<Option<<&'_ mut S as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<P> Stream for Pin<P> where
    P: DerefMut + Unpin,
    <P as Deref>::Target: Stream, 

type Item = <<P as Deref>::Target as Stream>::Item

pub fn poll_next(
    self: Pin<&mut Pin<P>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Pin<P> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<S> Stream for Box<S, Global> where
    S: Stream + Unpin + ?Sized, 

type Item = <S as Stream>::Item

pub fn poll_next(
    self: Pin<&mut Box<S, Global>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Box<S, Global> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<S> Stream for AssertUnwindSafe<S> where
    S: Stream, 

type Item = <S as Stream>::Item

pub fn poll_next(
    self: Pin<&mut AssertUnwindSafe<S>>,
    cx: &mut Context<'_>
) -> Poll<Option<<S as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

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Implementors

impl<A, B> Stream for Either<A, B> where
    B: Stream<Item = <A as Stream>::Item>,
    A: Stream, 

type Item = <A as Stream>::Item

pub fn poll_next(
    self: Pin<&mut Either<A, B>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Either<A, B> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<A, F> Stream for RepeatWith<F> where
    F: FnMut() -> A, 

type Item = A

pub fn poll_next(
    self: Pin<&mut RepeatWith<F>>,
    &mut Context<'_>
) -> Poll<Option<<RepeatWith<F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<B, St, S, Fut, F> Stream for Scan<St, S, Fut, F> where
    F: FnMut(&mut S, <St as Stream>::Item) -> Fut,
    Fut: Future<Output = Option<B>>,
    St: Stream, 

type Item = B

pub fn poll_next(
    self: Pin<&mut Scan<St, S, Fut, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<B>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<F> Stream for FlattenStream<F> where
    F: Future,
    Flatten<F, <F as Future>::Output>: Stream, 

type Item = <Flatten<F, <F as Future>::Output> as Stream>::Item

pub fn poll_next(
    self: Pin<&mut FlattenStream<F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<FlattenStream<F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<F> Stream for futures::future::IntoStream<F> where
    Once<F>: Stream, 

type Item = <Once<F> as Stream>::Item

pub fn poll_next(
    self: Pin<&mut IntoStream<F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<IntoStream<F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<Fut> Stream for TryFlattenStream<Fut> where
    Fut: TryFuture,
    TryFlatten<Fut, <Fut as TryFuture>::Ok>: Stream, 

type Item = <TryFlatten<Fut, <Fut as TryFuture>::Ok> as Stream>::Item

pub fn poll_next(
    self: Pin<&mut TryFlattenStream<Fut>>,
    cx: &mut Context<'_>
) -> Poll<Option<<TryFlattenStream<Fut> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<Fut> Stream for FuturesOrdered<Fut> where
    Fut: Future, 

type Item = <Fut as Future>::Output

pub fn poll_next(
    self: Pin<&mut FuturesOrdered<Fut>>,
    cx: &mut Context<'_>
) -> Poll<Option<<FuturesOrdered<Fut> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<Fut> Stream for FuturesUnordered<Fut> where
    Fut: Future, 

type Item = <Fut as Future>::Output

pub fn poll_next(
    self: Pin<&mut FuturesUnordered<Fut>>,
    cx: &mut Context<'_>
) -> Poll<Option<<FuturesUnordered<Fut> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<Fut> Stream for Once<Fut> where
    Fut: Future, 

type Item = <Fut as Future>::Output

pub fn poll_next(
    self: Pin<&mut Once<Fut>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Once<Fut> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<Fut, Si> Stream for FlattenSink<Fut, Si> where
    TryFlatten<Fut, Si>: Stream, 

type Item = <TryFlatten<Fut, Si> as Stream>::Item

pub fn poll_next(
    self: Pin<&mut FlattenSink<Fut, Si>>,
    cx: &mut Context<'_>
) -> Poll<Option<<FlattenSink<Fut, Si> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<I> Stream for Iter<I> where
    I: Iterator, 

type Item = <I as Iterator>::Item

pub fn poll_next(
    self: Pin<&mut Iter<I>>,
    &mut Context<'_>
) -> Poll<Option<<I as Iterator>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<R> Stream for Lines<R> where
    R: AsyncBufRead, 

type Item = Result<String, Error>

pub fn poll_next(
    self: Pin<&mut Lines<R>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Lines<R> as Stream>::Item>>

impl<S> Stream for Fuse<S> where
    S: Stream, 

type Item = <S as Stream>::Item

pub fn poll_next(
    self: Pin<&mut Fuse<S>>,
    cx: &mut Context<'_>
) -> Poll<Option<<S as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<S> Stream for Peekable<S> where
    S: Stream, 

type Item = <S as Stream>::Item

pub fn poll_next(
    self: Pin<&mut Peekable<S>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Peekable<S> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<S> Stream for SplitStream<S> where
    S: Stream, 

type Item = <S as Stream>::Item

pub fn poll_next(
    self: Pin<&mut SplitStream<S>>,
    cx: &mut Context<'_>
) -> Poll<Option<<S as Stream>::Item>>

impl<S, F> Stream for SinkMapErr<S, F> where
    S: Stream, 

type Item = <S as Stream>::Item

pub fn poll_next(
    self: Pin<&mut SinkMapErr<S, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<SinkMapErr<S, F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<S, Item> Stream for Buffer<S, Item> where
    S: Sink<Item> + Stream, 

type Item = <S as Stream>::Item

pub fn poll_next(
    self: Pin<&mut Buffer<S, Item>>,
    cx: &mut Context<'_>
) -> Poll<Option<<S as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<S, Item, E> Stream for SinkErrInto<S, Item, E> where
    S: Sink<Item> + Stream,
    <S as Sink<Item>>::Error: Into<E>, 

type Item = <S as Stream>::Item

pub fn poll_next(
    self: Pin<&mut SinkErrInto<S, Item, E>>,
    cx: &mut Context<'_>
) -> Poll<Option<<SinkErrInto<S, Item, E> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<S, Item, U, Fut, F> Stream for With<S, Item, U, Fut, F> where
    F: FnMut(U) -> Fut,
    Fut: Future,
    S: Stream + Sink<Item>, 

type Item = <S as Stream>::Item

pub fn poll_next(
    self: Pin<&mut With<S, Item, U, Fut, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<With<S, Item, U, Fut, F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<S, Item, U, St, F> Stream for WithFlatMap<S, Item, U, St, F> where
    F: FnMut(U) -> St,
    St: Stream<Item = Result<Item, <S as Sink<Item>>::Error>>,
    S: Stream + Sink<Item>, 

type Item = <S as Stream>::Item

pub fn poll_next(
    self: Pin<&mut WithFlatMap<S, Item, U, St, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<WithFlatMap<S, Item, U, St, F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<S, SinkItem> Stream for Compat01As03Sink<S, SinkItem> where
    S: Stream, 

type Item = Result<<S as Stream>::Item, <S as Stream>::Error>

pub fn poll_next(
    self: Pin<&mut Compat01As03Sink<S, SinkItem>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Compat01As03Sink<S, SinkItem> as Stream>::Item>>

impl<St1, St2> Stream for Chain<St1, St2> where
    St1: Stream,
    St2: Stream<Item = <St1 as Stream>::Item>, 

type Item = <St1 as Stream>::Item

pub fn poll_next(
    self: Pin<&mut Chain<St1, St2>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Chain<St1, St2> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St1, St2> Stream for Select<St1, St2> where
    St1: Stream,
    St2: Stream<Item = <St1 as Stream>::Item>, 

type Item = <St1 as Stream>::Item

pub fn poll_next(
    self: Pin<&mut Select<St1, St2>>,
    cx: &mut Context<'_>
) -> Poll<Option<<St1 as Stream>::Item>>

impl<St1, St2> Stream for Zip<St1, St2> where
    St1: Stream,
    St2: Stream, 

type Item = (<St1 as Stream>::Item, <St2 as Stream>::Item)

pub fn poll_next(
    self: Pin<&mut Zip<St1, St2>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Zip<St1, St2> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St> Stream for Compat01As03<St> where
    St: Stream, 

type Item = Result<<St as Stream>::Item, <St as Stream>::Error>

pub fn poll_next(
    self: Pin<&mut Compat01As03<St>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Compat01As03<St> as Stream>::Item>>

impl<St> Stream for BufferUnordered<St> where
    St: Stream,
    <St as Stream>::Item: Future, 

type Item = <<St as Stream>::Item as Future>::Output

pub fn poll_next(
    self: Pin<&mut BufferUnordered<St>>,
    cx: &mut Context<'_>
) -> Poll<Option<<BufferUnordered<St> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St> Stream for Buffered<St> where
    St: Stream,
    <St as Stream>::Item: Future, 

type Item = <<St as Stream>::Item as Future>::Output

pub fn poll_next(
    self: Pin<&mut Buffered<St>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Buffered<St> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St> Stream for CatchUnwind<St> where
    St: UnwindSafe + Stream, 

type Item = Result<<St as Stream>::Item, Box<dyn Any + 'static + Send, Global>>

pub fn poll_next(
    self: Pin<&mut CatchUnwind<St>>,
    cx: &mut Context<'_>
) -> Poll<Option<<CatchUnwind<St> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St> Stream for Chunks<St> where
    St: Stream, 

type Item = Vec<<St as Stream>::Item, Global>

pub fn poll_next(
    self: Pin<&mut Chunks<St>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Chunks<St> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St> Stream for Cycle<St> where
    St: Clone + Stream, 

type Item = <St as Stream>::Item

pub fn poll_next(
    self: Pin<&mut Cycle<St>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Cycle<St> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St> Stream for Enumerate<St> where
    St: Stream, 

type Item = (usize, <St as Stream>::Item)

pub fn poll_next(
    self: Pin<&mut Enumerate<St>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Enumerate<St> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St> Stream for Flatten<St> where
    St: Stream,
    Flatten<St, <St as Stream>::Item>: Stream, 

type Item = <Flatten<St, <St as Stream>::Item> as Stream>::Item

pub fn poll_next(
    self: Pin<&mut Flatten<St>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Flatten<St> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St> Stream for futures::stream::IntoStream<St> where
    St: TryStream, 

type Item = Result<<St as TryStream>::Ok, <St as TryStream>::Error>

pub fn poll_next(
    self: Pin<&mut IntoStream<St>>,
    cx: &mut Context<'_>
) -> Poll<Option<<IntoStream<St> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St> Stream for ReadyChunks<St> where
    St: Stream, 

type Item = Vec<<St as Stream>::Item, Global>

pub fn poll_next(
    self: Pin<&mut ReadyChunks<St>>,
    cx: &mut Context<'_>
) -> Poll<Option<<ReadyChunks<St> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St> Stream for SelectAll<St> where
    St: Unpin + Stream, 

type Item = <St as Stream>::Item

pub fn poll_next(
    self: Pin<&mut SelectAll<St>>,
    cx: &mut Context<'_>
) -> Poll<Option<<SelectAll<St> as Stream>::Item>>

impl<St> Stream for Skip<St> where
    St: Stream, 

type Item = <St as Stream>::Item

pub fn poll_next(
    self: Pin<&mut Skip<St>>,
    cx: &mut Context<'_>
) -> Poll<Option<<St as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St> Stream for Take<St> where
    St: Stream, 

type Item = <St as Stream>::Item

pub fn poll_next(
    self: Pin<&mut Take<St>>,
    cx: &mut Context<'_>
) -> Poll<Option<<St as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St> Stream for TryBufferUnordered<St> where
    St: TryStream,
    <St as TryStream>::Ok: TryFuture,
    <<St as TryStream>::Ok as TryFuture>::Error == <St as TryStream>::Error, 

type Item = Result<<<St as TryStream>::Ok as TryFuture>::Ok, <St as TryStream>::Error>

pub fn poll_next(
    self: Pin<&mut TryBufferUnordered<St>>,
    cx: &mut Context<'_>
) -> Poll<Option<<TryBufferUnordered<St> as Stream>::Item>>

impl<St> Stream for TryBuffered<St> where
    St: TryStream,
    <St as TryStream>::Ok: TryFuture,
    <<St as TryStream>::Ok as TryFuture>::Error == <St as TryStream>::Error, 

type Item = Result<<<St as TryStream>::Ok as TryFuture>::Ok, <St as TryStream>::Error>

pub fn poll_next(
    self: Pin<&mut TryBuffered<St>>,
    cx: &mut Context<'_>
) -> Poll<Option<<TryBuffered<St> as Stream>::Item>>

impl<St> Stream for TryFlatten<St> where
    St: TryStream,
    <St as TryStream>::Ok: TryStream,
    <<St as TryStream>::Ok as TryStream>::Error: From<<St as TryStream>::Error>, 

type Item = Result<<<St as TryStream>::Ok as TryStream>::Ok, <<St as TryStream>::Ok as TryStream>::Error>

pub fn poll_next(
    self: Pin<&mut TryFlatten<St>>,
    cx: &mut Context<'_>
) -> Poll<Option<<TryFlatten<St> as Stream>::Item>>

impl<St, E> Stream for ErrInto<St, E> where
    MapErr<St, IntoFn<E>>: Stream, 

type Item = <MapErr<St, IntoFn<E>> as Stream>::Item

pub fn poll_next(
    self: Pin<&mut ErrInto<St, E>>,
    cx: &mut Context<'_>
) -> Poll<Option<<ErrInto<St, E> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St, F> Stream for Inspect<St, F> where
    Map<St, InspectFn<F>>: Stream, 

type Item = <Map<St, InspectFn<F>> as Stream>::Item

pub fn poll_next(
    self: Pin<&mut Inspect<St, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Inspect<St, F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St, F> Stream for InspectErr<St, F> where
    Inspect<IntoStream<St>, InspectErrFn<F>>: Stream, 

type Item = <Inspect<IntoStream<St>, InspectErrFn<F>> as Stream>::Item

pub fn poll_next(
    self: Pin<&mut InspectErr<St, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<InspectErr<St, F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St, F> Stream for InspectOk<St, F> where
    Inspect<IntoStream<St>, InspectOkFn<F>>: Stream, 

type Item = <Inspect<IntoStream<St>, InspectOkFn<F>> as Stream>::Item

pub fn poll_next(
    self: Pin<&mut InspectOk<St, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<InspectOk<St, F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St, F> Stream for Map<St, F> where
    F: FnMut1<<St as Stream>::Item>,
    St: Stream, 

type Item = <F as FnOnce1<<St as Stream>::Item>>::Output

pub fn poll_next(
    self: Pin<&mut Map<St, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Map<St, F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St, F> Stream for MapErr<St, F> where
    Map<IntoStream<St>, MapErrFn<F>>: Stream, 

type Item = <Map<IntoStream<St>, MapErrFn<F>> as Stream>::Item

pub fn poll_next(
    self: Pin<&mut MapErr<St, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<MapErr<St, F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St, F> Stream for MapOk<St, F> where
    Map<IntoStream<St>, MapOkFn<F>>: Stream, 

type Item = <Map<IntoStream<St>, MapOkFn<F>> as Stream>::Item

pub fn poll_next(
    self: Pin<&mut MapOk<St, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<MapOk<St, F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St, Fut> Stream for TakeUntil<St, Fut> where
    Fut: Future,
    St: Stream, 

type Item = <St as Stream>::Item

pub fn poll_next(
    self: Pin<&mut TakeUntil<St, Fut>>,
    cx: &mut Context<'_>
) -> Poll<Option<<St as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St, Fut, F> Stream for AndThen<St, Fut, F> where
    F: FnMut(<St as TryStream>::Ok) -> Fut,
    Fut: TryFuture<Error = <St as TryStream>::Error>,
    St: TryStream, 

type Item = Result<<Fut as TryFuture>::Ok, <St as TryStream>::Error>

pub fn poll_next(
    self: Pin<&mut AndThen<St, Fut, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<AndThen<St, Fut, F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St, Fut, F> Stream for Filter<St, Fut, F> where
    F: for<'a> FnMut1<&'a <St as Stream>::Item, Output = Fut>,
    Fut: Future<Output = bool>,
    St: Stream, 

type Item = <St as Stream>::Item

pub fn poll_next(
    self: Pin<&mut Filter<St, Fut, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<St as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St, Fut, F> Stream for OrElse<St, Fut, F> where
    F: FnMut(<St as TryStream>::Error) -> Fut,
    Fut: TryFuture<Ok = <St as TryStream>::Ok>,
    St: TryStream, 

type Item = Result<<St as TryStream>::Ok, <Fut as TryFuture>::Error>

pub fn poll_next(
    self: Pin<&mut OrElse<St, Fut, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<OrElse<St, Fut, F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St, Fut, F> Stream for SkipWhile<St, Fut, F> where
    F: FnMut(&<St as Stream>::Item) -> Fut,
    Fut: Future<Output = bool>,
    St: Stream, 

type Item = <St as Stream>::Item

pub fn poll_next(
    self: Pin<&mut SkipWhile<St, Fut, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<St as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St, Fut, F> Stream for TakeWhile<St, Fut, F> where
    F: FnMut(&<St as Stream>::Item) -> Fut,
    Fut: Future<Output = bool>,
    St: Stream, 

type Item = <St as Stream>::Item

pub fn poll_next(
    self: Pin<&mut TakeWhile<St, Fut, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<St as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St, Fut, F> Stream for Then<St, Fut, F> where
    F: FnMut(<St as Stream>::Item) -> Fut,
    Fut: Future,
    St: Stream, 

type Item = <Fut as Future>::Output

pub fn poll_next(
    self: Pin<&mut Then<St, Fut, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Then<St, Fut, F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St, Fut, F> Stream for TryFilter<St, Fut, F> where
    F: FnMut(&<St as TryStream>::Ok) -> Fut,
    Fut: Future<Output = bool>,
    St: TryStream, 

type Item = Result<<St as TryStream>::Ok, <St as TryStream>::Error>

pub fn poll_next(
    self: Pin<&mut TryFilter<St, Fut, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<TryFilter<St, Fut, F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St, Fut, F> Stream for TrySkipWhile<St, Fut, F> where
    F: FnMut(&<St as TryStream>::Ok) -> Fut,
    Fut: TryFuture<Ok = bool, Error = <St as TryStream>::Error>,
    St: TryStream, 

type Item = Result<<St as TryStream>::Ok, <St as TryStream>::Error>

pub fn poll_next(
    self: Pin<&mut TrySkipWhile<St, Fut, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<TrySkipWhile<St, Fut, F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St, Fut, F> Stream for TryTakeWhile<St, Fut, F> where
    F: FnMut(&<St as TryStream>::Ok) -> Fut,
    Fut: TryFuture<Ok = bool, Error = <St as TryStream>::Error>,
    St: TryStream, 

type Item = Result<<St as TryStream>::Ok, <St as TryStream>::Error>

pub fn poll_next(
    self: Pin<&mut TryTakeWhile<St, Fut, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<TryTakeWhile<St, Fut, F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St, Fut, F, T> Stream for FilterMap<St, Fut, F> where
    F: FnMut1<<St as Stream>::Item, Output = Fut>,
    Fut: Future<Output = Option<T>>,
    St: Stream, 

type Item = T

pub fn poll_next(
    self: Pin<&mut FilterMap<St, Fut, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<T>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St, Fut, F, T> Stream for TryFilterMap<St, Fut, F> where
    F: FnMut(<St as TryStream>::Ok) -> Fut,
    Fut: TryFuture<Ok = Option<T>, Error = <St as TryStream>::Error>,
    St: TryStream, 

type Item = Result<T, <St as TryStream>::Error>

pub fn poll_next(
    self: Pin<&mut TryFilterMap<St, Fut, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<TryFilterMap<St, Fut, F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<St, U, F> Stream for FlatMap<St, U, F> where
    Flatten<Map<St, F>, U>: Stream, 

type Item = <Flatten<Map<St, F>, U> as Stream>::Item

pub fn poll_next(
    self: Pin<&mut FlatMap<St, U, F>>,
    cx: &mut Context<'_>
) -> Poll<Option<<FlatMap<St, U, F> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<T> Stream for Receiver<T>

type Item = T

pub fn poll_next(
    self: Pin<&mut Receiver<T>>,
    cx: &mut Context<'_>
) -> Poll<Option<T>>

impl<T> Stream for UnboundedReceiver<T>

type Item = T

pub fn poll_next(
    self: Pin<&mut UnboundedReceiver<T>>,
    cx: &mut Context<'_>
) -> Poll<Option<T>>

impl<T> Stream for Empty<T>

type Item = T

pub fn poll_next(
    self: Pin<&mut Empty<T>>,
    &mut Context<'_>
) -> Poll<Option<<Empty<T> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<T> Stream for Pending<T>

type Item = T

pub fn poll_next(
    self: Pin<&mut Pending<T>>,
    &mut Context<'_>
) -> Poll<Option<<Pending<T> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<T> Stream for Repeat<T> where
    T: Clone, 

type Item = T

pub fn poll_next(
    self: Pin<&mut Repeat<T>>,
    &mut Context<'_>
) -> Poll<Option<<Repeat<T> as Stream>::Item>>

pub fn size_hint(&self) -> (usize, Option<usize>)

impl<T, F> Stream for PollFn<F> where
    F: FnMut(&mut Context<'_>) -> Poll<Option<T>>, 

type Item = T

pub fn poll_next(
    self: Pin<&mut PollFn<F>>,
    cx: &mut Context<'_>
) -> Poll<Option<T>>

impl<T, F, Fut, Item> Stream for TryUnfold<T, F, Fut> where
    F: FnMut(T) -> Fut,
    Fut: TryFuture<Ok = Option<(Item, T)>>, 

type Item = Result<Item, <Fut as TryFuture>::Error>

pub fn poll_next(
    self: Pin<&mut TryUnfold<T, F, Fut>>,
    cx: &mut Context<'_>
) -> Poll<Option<<TryUnfold<T, F, Fut> as Stream>::Item>>

impl<T, F, Fut, Item> Stream for Unfold<T, F, Fut> where
    F: FnMut(T) -> Fut,
    Fut: Future<Output = Option<(Item, T)>>, 

type Item = Item

pub fn poll_next(
    self: Pin<&mut Unfold<T, F, Fut>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Unfold<T, F, Fut> as Stream>::Item>>

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