src/future/try_future/mod.rs - platform/external/rust/crates/futures-util - Git at Google

 //! Futures
 //!
 //! This module contains a number of functions for working with `Future`s,
 //! including the `FutureExt` trait which adds methods to `Future` types.

 #[cfg(feature = "compat")]
 use crate::compat::Compat;
 use core::pin::Pin;
 use futures_core::{
     future::TryFuture,
     stream::TryStream,
     task::{Context, Poll},
 };
 #[cfg(feature = "sink")]
 use futures_sink::Sink;

 use super::assert_future;
 use crate::future::{Map, Inspect};
 use crate::fns::{
     MapOkFn, map_ok_fn, MapErrFn, map_err_fn, MapOkOrElseFn,
     map_ok_or_else_fn, IntoFn, UnwrapOrElseFn, unwrap_or_else_fn, InspectOkFn, inspect_ok_fn, InspectErrFn,
     inspect_err_fn, into_fn
 };

 // Combinators
 mod into_future;
 mod try_flatten;
 mod try_flatten_err;

 delegate_all!(
     /// Future for the [`try_flatten`](TryFutureExt::try_flatten) method.
     TryFlatten<Fut1, Fut2>(
         try_flatten::TryFlatten<Fut1, Fut2>
     ): Debug + Future + FusedFuture + New[|x: Fut1| try_flatten::TryFlatten::new(x)]
 );

 delegate_all!(
     /// Future for the [`try_flatten_err`](TryFutureExt::try_flatten_err) method.
     TryFlattenErr<Fut1, Fut2>(
         try_flatten_err::TryFlattenErr<Fut1, Fut2>
     ): Debug + Future + FusedFuture + New[|x: Fut1| try_flatten_err::TryFlattenErr::new(x)]
 );

 delegate_all!(
     /// Future for the [`try_flatten_stream`](TryFutureExt::try_flatten_stream) method.
     TryFlattenStream<Fut>(
         try_flatten::TryFlatten<Fut, Fut::Ok>
     ): Debug + Sink + Stream + FusedStream + New[|x: Fut| try_flatten::TryFlatten::new(x)]
     where Fut: TryFuture
 );

 #[cfg(feature = "sink")]
 delegate_all!(
     /// Sink for the [`flatten_sink`](TryFutureExt::flatten_sink) method.
     FlattenSink<Fut, Si>(
         try_flatten::TryFlatten<Fut, Si>
     ): Debug + Sink + Stream + FusedStream + New[|x: Fut| try_flatten::TryFlatten::new(x)]
 );

 delegate_all!(
     /// Future for the [`and_then`](TryFutureExt::and_then) method.
     AndThen<Fut1, Fut2, F>(
         TryFlatten<MapOk<Fut1, F>, Fut2>
     ): Debug + Future + FusedFuture + New[|x: Fut1, f: F| TryFlatten::new(MapOk::new(x, f))]
 );

 delegate_all!(
     /// Future for the [`or_else`](TryFutureExt::or_else) method.
     OrElse<Fut1, Fut2, F>(
         TryFlattenErr<MapErr<Fut1, F>, Fut2>
     ): Debug + Future + FusedFuture + New[|x: Fut1, f: F| TryFlattenErr::new(MapErr::new(x, f))]
 );

 delegate_all!(
     /// Future for the [`err_into`](TryFutureExt::err_into) method.
     ErrInto<Fut, E>(
         MapErr<Fut, IntoFn<E>>
     ): Debug + Future + FusedFuture + New[|x: Fut| MapErr::new(x, into_fn())]
 );

 delegate_all!(
     /// Future for the [`ok_into`](TryFutureExt::ok_into) method.
     OkInto<Fut, E>(
         MapOk<Fut, IntoFn<E>>
     ): Debug + Future + FusedFuture + New[|x: Fut| MapOk::new(x, into_fn())]
 );

 delegate_all!(
     /// Future for the [`inspect_ok`](super::TryFutureExt::inspect_ok) method.
     InspectOk<Fut, F>(
         Inspect<IntoFuture<Fut>, InspectOkFn<F>>
     ): Debug + Future + FusedFuture + New[|x: Fut, f: F| Inspect::new(IntoFuture::new(x), inspect_ok_fn(f))]
 );

 delegate_all!(
     /// Future for the [`inspect_err`](super::TryFutureExt::inspect_err) method.
     InspectErr<Fut, F>(
         Inspect<IntoFuture<Fut>, InspectErrFn<F>>
     ): Debug + Future + FusedFuture + New[|x: Fut, f: F| Inspect::new(IntoFuture::new(x), inspect_err_fn(f))]
 );

 #[allow(unreachable_pub)] // https://github.com/rust-lang/rust/issues/57411
 pub use self::into_future::IntoFuture;

 delegate_all!(
     /// Future for the [`map_ok`](TryFutureExt::map_ok) method.
     MapOk<Fut, F>(
         Map<IntoFuture<Fut>, MapOkFn<F>>
     ): Debug + Future + FusedFuture + New[|x: Fut, f: F| Map::new(IntoFuture::new(x), map_ok_fn(f))]
 );

 delegate_all!(
     /// Future for the [`map_err`](TryFutureExt::map_err) method.
     MapErr<Fut, F>(
         Map<IntoFuture<Fut>, MapErrFn<F>>
     ): Debug + Future + FusedFuture + New[|x: Fut, f: F| Map::new(IntoFuture::new(x), map_err_fn(f))]
 );

 delegate_all!(
     /// Future for the [`map_ok_or_else`](TryFutureExt::map_ok_or_else) method.
     MapOkOrElse<Fut, F, G>(
         Map<IntoFuture<Fut>, MapOkOrElseFn<F, G>>
     ): Debug + Future + FusedFuture + New[|x: Fut, f: F, g: G| Map::new(IntoFuture::new(x), map_ok_or_else_fn(f, g))]
 );

 delegate_all!(
     /// Future for the [`unwrap_or_else`](TryFutureExt::unwrap_or_else) method.
     UnwrapOrElse<Fut, F>(
         Map<IntoFuture<Fut>, UnwrapOrElseFn<F>>
     ): Debug + Future + FusedFuture + New[|x: Fut, f: F| Map::new(IntoFuture::new(x), unwrap_or_else_fn(f))]
 );

 impl<Fut: ?Sized + TryFuture> TryFutureExt for Fut {}

 /// Adapters specific to [`Result`]-returning futures
 pub trait TryFutureExt: TryFuture {
     /// Flattens the execution of this future when the successful result of this
     /// future is a [`Sink`].
     ///
     /// This can be useful when sink initialization is deferred, and it is
     /// convenient to work with that sink as if the sink was available at the
     /// call site.
     ///
     /// Note that this function consumes this future and returns a wrapped
     /// version of it.
     ///
     /// # Examples
     ///
     /// ```
     /// use futures::future::{Future, TryFutureExt};
     /// use futures::sink::Sink;
     /// # use futures::channel::mpsc::{self, SendError};
     /// # type T = i32;
     /// # type E = SendError;
     ///
     /// fn make_sink_async() -> impl Future<Output = Result<
     ///     impl Sink<T, Error = E>,
     ///     E,
     /// >> { // ... }
     /// # let (tx, _rx) = mpsc::unbounded::<i32>();
     /// # futures::future::ready(Ok(tx))
     /// # }
     /// fn take_sink(sink: impl Sink<T, Error = E>) { /* ... */ }
     ///
     /// let fut = make_sink_async();
     /// take_sink(fut.flatten_sink())
     /// ```
     #[cfg(feature = "sink")]
     fn flatten_sink<Item>(self) -> FlattenSink<Self, Self::Ok>
     where
         Self::Ok: Sink<Item, Error = Self::Error>,
         Self: Sized,
     {
         FlattenSink::new(self)
     }

     /// Maps this future's success value to a different value.
     ///
     /// This method can be used to change the [`Ok`](TryFuture::Ok) type of the
     /// future into a different type. It is similar to the [`Result::map`]
     /// method. You can use this method to chain along a computation once the
     /// future has been resolved.
     ///
     /// The provided closure `f` will only be called if this future is resolved
     /// to an [`Ok`]. If it resolves to an [`Err`], panics, or is dropped, then
     /// the provided closure will never be invoked.
     ///
     /// Note that this method consumes the future it is called on and returns a
     /// wrapped version of it.
     ///
     /// # Examples
     ///
     /// ```
     /// use futures::future::TryFutureExt;
     ///
     /// # futures::executor::block_on(async {
     /// let future = async { Ok::<i32, i32>(1) };
     /// let future = future.map_ok(|x| x + 3);
     /// assert_eq!(future.await, Ok(4));
     /// # });
     /// ```
     ///
     /// Calling [`map_ok`](TryFutureExt::map_ok) on an errored future has no
     /// effect:
     ///
     /// ```
     /// use futures::future::TryFutureExt;
     ///
     /// # futures::executor::block_on(async {
     /// let future = async { Err::<i32, i32>(1) };
     /// let future = future.map_ok(|x| x + 3);
     /// assert_eq!(future.await, Err(1));
     /// # });
     /// ```
     fn map_ok<T, F>(self, f: F) -> MapOk<Self, F>
     where
         F: FnOnce(Self::Ok) -> T,
         Self: Sized,
     {
         assert_future::<Result<T, Self::Error>, _>(MapOk::new(self, f))
     }

     /// Maps this future's success value to a different value, and permits for error handling resulting in the same type.
     ///
     /// This method can be used to coalesce your [`Ok`](TryFuture::Ok) type and [`Error`](TryFuture::Error) into another type,
     /// where that type is the same for both outcomes.
     ///
     /// The provided closure `f` will only be called if this future is resolved
     /// to an [`Ok`]. If it resolves to an [`Err`], panics, or is dropped, then
     /// the provided closure will never be invoked.
     ///
     /// The provided closure `e` will only be called if this future is resolved
     /// to an [`Err`]. If it resolves to an [`Ok`], panics, or is dropped, then
     /// the provided closure will never be invoked.
     ///
     /// Note that this method consumes the future it is called on and returns a
     /// wrapped version of it.
     ///
     /// # Examples
     ///
     /// ```
     /// use futures::future::TryFutureExt;
     ///
     /// # futures::executor::block_on(async {
     /// let future = async { Ok::<i32, i32>(5) };
     /// let future = future.map_ok_or_else(|x| x * 2, |x| x + 3);
     /// assert_eq!(future.await, 8);
     ///
     /// let future = async { Err::<i32, i32>(5) };
     /// let future = future.map_ok_or_else(|x| x * 2, |x| x + 3);
     /// assert_eq!(future.await, 10);
     /// # });
     /// ```
     ///
     fn map_ok_or_else<T, E, F>(self, e: E, f: F) -> MapOkOrElse<Self, F, E>
     where
         F: FnOnce(Self::Ok) -> T,
         E: FnOnce(Self::Error) -> T,
         Self: Sized,
     {
         assert_future::<T, _>(MapOkOrElse::new(self, f, e))
     }

     /// Maps this future's error value to a different value.
     ///
     /// This method can be used to change the [`Error`](TryFuture::Error) type
     /// of the future into a different type. It is similar to the
     /// [`Result::map_err`] method. You can use this method for example to
     /// ensure that futures have the same [`Error`](TryFuture::Error) type when
     /// using [`select!`] or [`join!`].
     ///
     /// The provided closure `f` will only be called if this future is resolved
     /// to an [`Err`]. If it resolves to an [`Ok`], panics, or is dropped, then
     /// the provided closure will never be invoked.
     ///
     /// Note that this method consumes the future it is called on and returns a
     /// wrapped version of it.
     ///
     /// # Examples
     ///
     /// ```
     /// use futures::future::TryFutureExt;
     ///
     /// # futures::executor::block_on(async {
     /// let future = async { Err::<i32, i32>(1) };
     /// let future = future.map_err(|x| x + 3);
     /// assert_eq!(future.await, Err(4));
     /// # });
     /// ```
     ///
     /// Calling [`map_err`](TryFutureExt::map_err) on a successful future has
     /// no effect:
     ///
     /// ```
     /// use futures::future::TryFutureExt;
     ///
     /// # futures::executor::block_on(async {
     /// let future = async { Ok::<i32, i32>(1) };
     /// let future = future.map_err(|x| x + 3);
     /// assert_eq!(future.await, Ok(1));
     /// # });
     /// ```
     fn map_err<E, F>(self, f: F) -> MapErr<Self, F>
     where
         F: FnOnce(Self::Error) -> E,
         Self: Sized,
     {
         assert_future::<Result<Self::Ok, E>, _>(MapErr::new(self, f))
     }

     /// Maps this future's [`Error`](TryFuture::Error) to a new error type
     /// using the [`Into`](std::convert::Into) trait.
     ///
     /// This method does for futures what the `?`-operator does for
     /// [`Result`]: It lets the compiler infer the type of the resulting
     /// error. Just as [`map_err`](TryFutureExt::map_err), this is useful for
     /// example to ensure that futures have the same [`Error`](TryFuture::Error)
     /// type when using [`select!`] or [`join!`].
     ///
     /// Note that this method consumes the future it is called on and returns a
     /// wrapped version of it.
     ///
     /// # Examples
     ///
     /// ```
     /// use futures::future::TryFutureExt;
     ///
     /// # futures::executor::block_on(async {
     /// let future_err_u8 = async { Err::<(), u8>(1) };
     /// let future_err_i32 = future_err_u8.err_into::<i32>();
     /// # });
     /// ```
     fn err_into<E>(self) -> ErrInto<Self, E>
     where
         Self: Sized,
         Self::Error: Into<E>,
     {
         assert_future::<Result<Self::Ok, E>, _>(ErrInto::new(self))
     }

     /// Maps this future's [`Ok`](TryFuture::Ok) to a new type
     /// using the [`Into`](std::convert::Into) trait.
     fn ok_into<U>(self) -> OkInto<Self, U>
     where
         Self: Sized,
         Self::Ok: Into<U>,
     {
         assert_future::<Result<U, Self::Error>, _>(OkInto::new(self))
     }

     /// Executes another future after this one resolves successfully. The
     /// success value is passed to a closure to create this subsequent future.
     ///
     /// The provided closure `f` will only be called if this future is resolved
     /// to an [`Ok`]. If this future resolves to an [`Err`], panics, or is
     /// dropped, then the provided closure will never be invoked. The
     /// [`Error`](TryFuture::Error) type of this future and the future
     /// returned by `f` have to match.
     ///
     /// Note that this method consumes the future it is called on and returns a
     /// wrapped version of it.
     ///
     /// # Examples
     ///
     /// ```
     /// use futures::future::TryFutureExt;
     ///
     /// # futures::executor::block_on(async {
     /// let future = async { Ok::<i32, i32>(1) };
     /// let future = future.and_then(|x| async move { Ok::<i32, i32>(x + 3) });
     /// assert_eq!(future.await, Ok(4));
     /// # });
     /// ```
     ///
     /// Calling [`and_then`](TryFutureExt::and_then) on an errored future has no
     /// effect:
     ///
     /// ```
     /// use futures::future::TryFutureExt;
     ///
     /// # futures::executor::block_on(async {
     /// let future = async { Err::<i32, i32>(1) };
     /// let future = future.and_then(|x| async move { Err::<i32, i32>(x + 3) });
     /// assert_eq!(future.await, Err(1));
     /// # });
     /// ```
     fn and_then<Fut, F>(self, f: F) -> AndThen<Self, Fut, F>
     where
         F: FnOnce(Self::Ok) -> Fut,
         Fut: TryFuture<Error = Self::Error>,
         Self: Sized,
     {
         assert_future::<Result<Fut::Ok, Fut::Error>, _>(AndThen::new(self, f))
     }

     /// Executes another future if this one resolves to an error. The
     /// error value is passed to a closure to create this subsequent future.
     ///
     /// The provided closure `f` will only be called if this future is resolved
     /// to an [`Err`]. If this future resolves to an [`Ok`], panics, or is
     /// dropped, then the provided closure will never be invoked. The
     /// [`Ok`](TryFuture::Ok) type of this future and the future returned by `f`
     /// have to match.
     ///
     /// Note that this method consumes the future it is called on and returns a
     /// wrapped version of it.
     ///
     /// # Examples
     ///
     /// ```
     /// use futures::future::TryFutureExt;
     ///
     /// # futures::executor::block_on(async {
     /// let future = async { Err::<i32, i32>(1) };
     /// let future = future.or_else(|x| async move { Err::<i32, i32>(x + 3) });
     /// assert_eq!(future.await, Err(4));
     /// # });
     /// ```
     ///
     /// Calling [`or_else`](TryFutureExt::or_else) on a successful future has
     /// no effect:
     ///
     /// ```
     /// use futures::future::TryFutureExt;
     ///
     /// # futures::executor::block_on(async {
     /// let future = async { Ok::<i32, i32>(1) };
     /// let future = future.or_else(|x| async move { Ok::<i32, i32>(x + 3) });
     /// assert_eq!(future.await, Ok(1));
     /// # });
     /// ```
     fn or_else<Fut, F>(self, f: F) -> OrElse<Self, Fut, F>
     where
         F: FnOnce(Self::Error) -> Fut,
         Fut: TryFuture<Ok = Self::Ok>,
         Self: Sized,
     {
         assert_future::<Result<Fut::Ok, Fut::Error>, _>(OrElse::new(self, f))
     }

     /// Do something with the success value of a future before passing it on.
     ///
     /// When using futures, you'll often chain several of them together.  While
     /// working on such code, you might want to check out what's happening at
     /// various parts in the pipeline, without consuming the intermediate
     /// value. To do that, insert a call to `inspect_ok`.
     ///
     /// # Examples
     ///
     /// ```
     /// # futures::executor::block_on(async {
     /// use futures::future::TryFutureExt;
     ///
     /// let future = async { Ok::<_, ()>(1) };
     /// let new_future = future.inspect_ok(|&x| println!("about to resolve: {}", x));
     /// assert_eq!(new_future.await, Ok(1));
     /// # });
     /// ```
     fn inspect_ok<F>(self, f: F) -> InspectOk<Self, F>
     where
         F: FnOnce(&Self::Ok),
         Self: Sized,
     {
         assert_future::<Result<Self::Ok, Self::Error>, _>(InspectOk::new(self, f))
     }

     /// Do something with the error value of a future before passing it on.
     ///
     /// When using futures, you'll often chain several of them together.  While
     /// working on such code, you might want to check out what's happening at
     /// various parts in the pipeline, without consuming the intermediate
     /// value. To do that, insert a call to `inspect_err`.
     ///
     /// # Examples
     ///
     /// ```
     /// # futures::executor::block_on(async {
     /// use futures::future::TryFutureExt;
     ///
     /// let future = async { Err::<(), _>(1) };
     /// let new_future = future.inspect_err(|&x| println!("about to error: {}", x));
     /// assert_eq!(new_future.await, Err(1));
     /// # });
     /// ```
     fn inspect_err<F>(self, f: F) -> InspectErr<Self, F>
     where
         F: FnOnce(&Self::Error),
         Self: Sized,
     {
         assert_future::<Result<Self::Ok, Self::Error>, _>(InspectErr::new(self, f))
     }

     /// Flatten the execution of this future when the successful result of this
     /// future is another future.
     ///
     /// This is equivalent to `future.and_then(|x| x)`.
     fn try_flatten(self) -> TryFlatten<Self, Self::Ok>
     where
         Self::Ok: TryFuture<Error = Self::Error>,
         Self: Sized,
     {
         TryFlatten::new(self)
     }

     /// Flatten the execution of this future when the successful result of this
     /// future is a stream.
     ///
     /// This can be useful when stream initialization is deferred, and it is
     /// convenient to work with that stream as if stream was available at the
     /// call site.
     ///
     /// Note that this function consumes this future and returns a wrapped
     /// version of it.
     ///
     /// # Examples
     ///
     /// ```
     /// # futures::executor::block_on(async {
     /// use futures::future::TryFutureExt;
     /// use futures::stream::{self, TryStreamExt};
     ///
     /// let stream_items = vec![17, 18, 19].into_iter().map(Ok);
     /// let future_of_a_stream = async { Ok::<_, ()>(stream::iter(stream_items)) };
     ///
     /// let stream = future_of_a_stream.try_flatten_stream();
     /// let list = stream.try_collect::<Vec<_>>().await;
     /// assert_eq!(list, Ok(vec![17, 18, 19]));
     /// # });
     /// ```
     fn try_flatten_stream(self) -> TryFlattenStream<Self>
     where
         Self::Ok: TryStream<Error = Self::Error>,
         Self: Sized,
     {
         TryFlattenStream::new(self)
     }

     /// Unwraps this future's ouput, producing a future with this future's
     /// [`Ok`](TryFuture::Ok) type as its
     /// [`Output`](std::future::Future::Output) type.
     ///
     /// If this future is resolved successfully, the returned future will
     /// contain the original future's success value as output. Otherwise, the
     /// closure `f` is called with the error value to produce an alternate
     /// success value.
     ///
     /// This method is similar to the [`Result::unwrap_or_else`] method.
     ///
     /// # Examples
     ///
     /// ```
     /// use futures::future::TryFutureExt;
     ///
     /// # futures::executor::block_on(async {
     /// let future = async { Err::<(), &str>("Boom!") };
     /// let future = future.unwrap_or_else(|_| ());
     /// assert_eq!(future.await, ());
     /// # });
     /// ```
     fn unwrap_or_else<F>(self, f: F) -> UnwrapOrElse<Self, F>
     where
         Self: Sized,
         F: FnOnce(Self::Error) -> Self::Ok,
     {
         assert_future::<Self::Ok, _>(UnwrapOrElse::new(self, f))
     }

     /// Wraps a [`TryFuture`] into a future compatable with libraries using
     /// futures 0.1 future definitons. Requires the `compat` feature to enable.
     #[cfg(feature = "compat")]
     fn compat(self) -> Compat<Self>
     where
         Self: Sized + Unpin,
     {
         Compat::new(self)
     }

     /// Wraps a [`TryFuture`] into a type that implements
     /// [`Future`](std::future::Future).
     ///
     /// [`TryFuture`]s currently do not implement the
     /// [`Future`](std::future::Future) trait due to limitations of the
     /// compiler.
     ///
     /// # Examples
     ///
     /// ```
     /// use futures::future::{Future, TryFuture, TryFutureExt};
     ///
     /// # type T = i32;
     /// # type E = ();
     /// fn make_try_future() -> impl TryFuture<Ok = T, Error = E> { // ... }
     /// # async { Ok::<i32, ()>(1) }
     /// # }
     /// fn take_future(future: impl Future<Output = Result<T, E>>) { /* ... */ }
     ///
     /// take_future(make_try_future().into_future());
     /// ```
     fn into_future(self) -> IntoFuture<Self>
     where
         Self: Sized,
     {
         IntoFuture::new(self)
     }

     /// A convenience method for calling [`TryFuture::try_poll`] on [`Unpin`]
     /// future types.
     fn try_poll_unpin(&mut self, cx: &mut Context<'_>) -> Poll<Result<Self::Ok, Self::Error>>
     where
         Self: Unpin,
     {
         Pin::new(self).try_poll(cx)
     }
 }
	//! Futures
	//!
	//! This module contains a number of functions for working with `Future`s,
	//! including the `FutureExt` trait which adds methods to `Future` types.

	#[cfg(feature = "compat")]
	use crate::compat::Compat;
	use core::pin::Pin;
	use futures_core::{
	future::TryFuture,
	stream::TryStream,
	task::{Context, Poll},
	};
	#[cfg(feature = "sink")]
	use futures_sink::Sink;

	use super::assert_future;
	use crate::future::{Map, Inspect};
	use crate::fns::{
	MapOkFn, map_ok_fn, MapErrFn, map_err_fn, MapOkOrElseFn,
	map_ok_or_else_fn, IntoFn, UnwrapOrElseFn, unwrap_or_else_fn, InspectOkFn, inspect_ok_fn, InspectErrFn,
	inspect_err_fn, into_fn
	};

	// Combinators
	mod into_future;
	mod try_flatten;
	mod try_flatten_err;

	delegate_all!(
	/// Future for the [`try_flatten`](TryFutureExt::try_flatten) method.
	TryFlatten<Fut1, Fut2>(
	try_flatten::TryFlatten<Fut1, Fut2>
	): Debug + Future + FusedFuture + New[\|x: Fut1\| try_flatten::TryFlatten::new(x)]
	);

	delegate_all!(
	/// Future for the [`try_flatten_err`](TryFutureExt::try_flatten_err) method.
	TryFlattenErr<Fut1, Fut2>(
	try_flatten_err::TryFlattenErr<Fut1, Fut2>
	): Debug + Future + FusedFuture + New[\|x: Fut1\| try_flatten_err::TryFlattenErr::new(x)]
	);

	delegate_all!(
	/// Future for the [`try_flatten_stream`](TryFutureExt::try_flatten_stream) method.
	TryFlattenStream<Fut>(
	try_flatten::TryFlatten<Fut, Fut::Ok>
	): Debug + Sink + Stream + FusedStream + New[\|x: Fut\| try_flatten::TryFlatten::new(x)]
	where Fut: TryFuture
	);

	#[cfg(feature = "sink")]
	delegate_all!(
	/// Sink for the [`flatten_sink`](TryFutureExt::flatten_sink) method.
	FlattenSink<Fut, Si>(
	try_flatten::TryFlatten<Fut, Si>
	): Debug + Sink + Stream + FusedStream + New[\|x: Fut\| try_flatten::TryFlatten::new(x)]
	);

	delegate_all!(
	/// Future for the [`and_then`](TryFutureExt::and_then) method.
	AndThen<Fut1, Fut2, F>(
	TryFlatten<MapOk<Fut1, F>, Fut2>
	): Debug + Future + FusedFuture + New[\|x: Fut1, f: F\| TryFlatten::new(MapOk::new(x, f))]
	);

	delegate_all!(
	/// Future for the [`or_else`](TryFutureExt::or_else) method.
	OrElse<Fut1, Fut2, F>(
	TryFlattenErr<MapErr<Fut1, F>, Fut2>
	): Debug + Future + FusedFuture + New[\|x: Fut1, f: F\| TryFlattenErr::new(MapErr::new(x, f))]
	);

	delegate_all!(
	/// Future for the [`err_into`](TryFutureExt::err_into) method.
	ErrInto<Fut, E>(
	MapErr<Fut, IntoFn<E>>
	): Debug + Future + FusedFuture + New[\|x: Fut\| MapErr::new(x, into_fn())]
	);

	delegate_all!(
	/// Future for the [`ok_into`](TryFutureExt::ok_into) method.
	OkInto<Fut, E>(
	MapOk<Fut, IntoFn<E>>
	): Debug + Future + FusedFuture + New[\|x: Fut\| MapOk::new(x, into_fn())]
	);

	delegate_all!(
	/// Future for the [`inspect_ok`](super::TryFutureExt::inspect_ok) method.
	InspectOk<Fut, F>(
	Inspect<IntoFuture<Fut>, InspectOkFn<F>>
	): Debug + Future + FusedFuture + New[\|x: Fut, f: F\| Inspect::new(IntoFuture::new(x), inspect_ok_fn(f))]
	);

	delegate_all!(
	/// Future for the [`inspect_err`](super::TryFutureExt::inspect_err) method.
	InspectErr<Fut, F>(
	Inspect<IntoFuture<Fut>, InspectErrFn<F>>
	): Debug + Future + FusedFuture + New[\|x: Fut, f: F\| Inspect::new(IntoFuture::new(x), inspect_err_fn(f))]
	);

	#[allow(unreachable_pub)] // https://github.com/rust-lang/rust/issues/57411
	pub use self::into_future::IntoFuture;

	delegate_all!(
	/// Future for the [`map_ok`](TryFutureExt::map_ok) method.
	MapOk<Fut, F>(
	Map<IntoFuture<Fut>, MapOkFn<F>>
	): Debug + Future + FusedFuture + New[\|x: Fut, f: F\| Map::new(IntoFuture::new(x), map_ok_fn(f))]
	);

	delegate_all!(
	/// Future for the [`map_err`](TryFutureExt::map_err) method.
	MapErr<Fut, F>(
	Map<IntoFuture<Fut>, MapErrFn<F>>
	): Debug + Future + FusedFuture + New[\|x: Fut, f: F\| Map::new(IntoFuture::new(x), map_err_fn(f))]
	);

	delegate_all!(
	/// Future for the [`map_ok_or_else`](TryFutureExt::map_ok_or_else) method.
	MapOkOrElse<Fut, F, G>(
	Map<IntoFuture<Fut>, MapOkOrElseFn<F, G>>
	): Debug + Future + FusedFuture + New[\|x: Fut, f: F, g: G\| Map::new(IntoFuture::new(x), map_ok_or_else_fn(f, g))]
	);

	delegate_all!(
	/// Future for the [`unwrap_or_else`](TryFutureExt::unwrap_or_else) method.
	UnwrapOrElse<Fut, F>(
	Map<IntoFuture<Fut>, UnwrapOrElseFn<F>>
	): Debug + Future + FusedFuture + New[\|x: Fut, f: F\| Map::new(IntoFuture::new(x), unwrap_or_else_fn(f))]
	);

	impl<Fut: ?Sized + TryFuture> TryFutureExt for Fut {}

	/// Adapters specific to [`Result`]-returning futures
	pub trait TryFutureExt: TryFuture {
	/// Flattens the execution of this future when the successful result of this
	/// future is a [`Sink`].
	///
	/// This can be useful when sink initialization is deferred, and it is
	/// convenient to work with that sink as if the sink was available at the
	/// call site.
	///
	/// Note that this function consumes this future and returns a wrapped
	/// version of it.
	///
	/// # Examples
	///
	/// ```
	/// use futures::future::{Future, TryFutureExt};
	/// use futures::sink::Sink;
	/// # use futures::channel::mpsc::{self, SendError};
	/// # type T = i32;
	/// # type E = SendError;
	///
	/// fn make_sink_async() -> impl Future<Output = Result<
	/// impl Sink<T, Error = E>,
	/// E,
	/// >> { // ... }
	/// # let (tx, _rx) = mpsc::unbounded::<i32>();
	/// # futures::future::ready(Ok(tx))
	/// # }
	/// fn take_sink(sink: impl Sink<T, Error = E>) { /* ... */ }
	///
	/// let fut = make_sink_async();
	/// take_sink(fut.flatten_sink())
	/// ```
	#[cfg(feature = "sink")]
	fn flatten_sink<Item>(self) -> FlattenSink<Self, Self::Ok>
	where
	Self::Ok: Sink<Item, Error = Self::Error>,
	Self: Sized,
	{
	FlattenSink::new(self)
	}

	/// Maps this future's success value to a different value.
	///
	/// This method can be used to change the [`Ok`](TryFuture::Ok) type of the
	/// future into a different type. It is similar to the [`Result::map`]
	/// method. You can use this method to chain along a computation once the
	/// future has been resolved.
	///
	/// The provided closure `f` will only be called if this future is resolved
	/// to an [`Ok`]. If it resolves to an [`Err`], panics, or is dropped, then
	/// the provided closure will never be invoked.
	///
	/// Note that this method consumes the future it is called on and returns a
	/// wrapped version of it.
	///
	/// # Examples
	///
	/// ```
	/// use futures::future::TryFutureExt;
	///
	/// # futures::executor::block_on(async {
	/// let future = async { Ok::<i32, i32>(1) };
	/// let future = future.map_ok(\|x\| x + 3);
	/// assert_eq!(future.await, Ok(4));
	/// # });
	/// ```
	///
	/// Calling [`map_ok`](TryFutureExt::map_ok) on an errored future has no
	/// effect:
	///
	/// ```
	/// use futures::future::TryFutureExt;
	///
	/// # futures::executor::block_on(async {
	/// let future = async { Err::<i32, i32>(1) };
	/// let future = future.map_ok(\|x\| x + 3);
	/// assert_eq!(future.await, Err(1));
	/// # });
	/// ```
	fn map_ok<T, F>(self, f: F) -> MapOk<Self, F>
	where
	F: FnOnce(Self::Ok) -> T,
	Self: Sized,
	{
	assert_future::<Result<T, Self::Error>, _>(MapOk::new(self, f))
	}

	/// Maps this future's success value to a different value, and permits for error handling resulting in the same type.
	///
	/// This method can be used to coalesce your [`Ok`](TryFuture::Ok) type and [`Error`](TryFuture::Error) into another type,
	/// where that type is the same for both outcomes.
	///
	/// The provided closure `f` will only be called if this future is resolved
	/// to an [`Ok`]. If it resolves to an [`Err`], panics, or is dropped, then
	/// the provided closure will never be invoked.
	///
	/// The provided closure `e` will only be called if this future is resolved
	/// to an [`Err`]. If it resolves to an [`Ok`], panics, or is dropped, then
	/// the provided closure will never be invoked.
	///
	/// Note that this method consumes the future it is called on and returns a
	/// wrapped version of it.
	///
	/// # Examples
	///
	/// ```
	/// use futures::future::TryFutureExt;
	///
	/// # futures::executor::block_on(async {
	/// let future = async { Ok::<i32, i32>(5) };
	/// let future = future.map_ok_or_else(\|x\| x * 2, \|x\| x + 3);
	/// assert_eq!(future.await, 8);
	///
	/// let future = async { Err::<i32, i32>(5) };
	/// let future = future.map_ok_or_else(\|x\| x * 2, \|x\| x + 3);
	/// assert_eq!(future.await, 10);
	/// # });
	/// ```
	///
	fn map_ok_or_else<T, E, F>(self, e: E, f: F) -> MapOkOrElse<Self, F, E>
	where
	F: FnOnce(Self::Ok) -> T,
	E: FnOnce(Self::Error) -> T,
	Self: Sized,
	{
	assert_future::<T, _>(MapOkOrElse::new(self, f, e))
	}

	/// Maps this future's error value to a different value.
	///
	/// This method can be used to change the [`Error`](TryFuture::Error) type
	/// of the future into a different type. It is similar to the
	/// [`Result::map_err`] method. You can use this method for example to
	/// ensure that futures have the same [`Error`](TryFuture::Error) type when
	/// using [`select!`] or [`join!`].
	///
	/// The provided closure `f` will only be called if this future is resolved
	/// to an [`Err`]. If it resolves to an [`Ok`], panics, or is dropped, then
	/// the provided closure will never be invoked.
	///
	/// Note that this method consumes the future it is called on and returns a
	/// wrapped version of it.
	///
	/// # Examples
	///
	/// ```
	/// use futures::future::TryFutureExt;
	///
	/// # futures::executor::block_on(async {
	/// let future = async { Err::<i32, i32>(1) };
	/// let future = future.map_err(\|x\| x + 3);
	/// assert_eq!(future.await, Err(4));
	/// # });
	/// ```
	///
	/// Calling [`map_err`](TryFutureExt::map_err) on a successful future has
	/// no effect:
	///
	/// ```
	/// use futures::future::TryFutureExt;
	///
	/// # futures::executor::block_on(async {
	/// let future = async { Ok::<i32, i32>(1) };
	/// let future = future.map_err(\|x\| x + 3);
	/// assert_eq!(future.await, Ok(1));
	/// # });
	/// ```
	fn map_err<E, F>(self, f: F) -> MapErr<Self, F>
	where
	F: FnOnce(Self::Error) -> E,
	Self: Sized,
	{
	assert_future::<Result<Self::Ok, E>, _>(MapErr::new(self, f))
	}

	/// Maps this future's [`Error`](TryFuture::Error) to a new error type
	/// using the [`Into`](std::convert::Into) trait.
	///
	/// This method does for futures what the `?`-operator does for
	/// [`Result`]: It lets the compiler infer the type of the resulting
	/// error. Just as [`map_err`](TryFutureExt::map_err), this is useful for
	/// example to ensure that futures have the same [`Error`](TryFuture::Error)
	/// type when using [`select!`] or [`join!`].
	///
	/// Note that this method consumes the future it is called on and returns a
	/// wrapped version of it.
	///
	/// # Examples
	///
	/// ```
	/// use futures::future::TryFutureExt;
	///
	/// # futures::executor::block_on(async {
	/// let future_err_u8 = async { Err::<(), u8>(1) };
	/// let future_err_i32 = future_err_u8.err_into::<i32>();
	/// # });
	/// ```
	fn err_into<E>(self) -> ErrInto<Self, E>
	where
	Self: Sized,
	Self::Error: Into<E>,
	{
	assert_future::<Result<Self::Ok, E>, _>(ErrInto::new(self))
	}

	/// Maps this future's [`Ok`](TryFuture::Ok) to a new type
	/// using the [`Into`](std::convert::Into) trait.
	fn ok_into<U>(self) -> OkInto<Self, U>
	where
	Self: Sized,
	Self::Ok: Into<U>,
	{
	assert_future::<Result<U, Self::Error>, _>(OkInto::new(self))
	}

	/// Executes another future after this one resolves successfully. The
	/// success value is passed to a closure to create this subsequent future.
	///
	/// The provided closure `f` will only be called if this future is resolved
	/// to an [`Ok`]. If this future resolves to an [`Err`], panics, or is
	/// dropped, then the provided closure will never be invoked. The
	/// [`Error`](TryFuture::Error) type of this future and the future
	/// returned by `f` have to match.
	///
	/// Note that this method consumes the future it is called on and returns a
	/// wrapped version of it.
	///
	/// # Examples
	///
	/// ```
	/// use futures::future::TryFutureExt;
	///
	/// # futures::executor::block_on(async {
	/// let future = async { Ok::<i32, i32>(1) };
	/// let future = future.and_then(\|x\| async move { Ok::<i32, i32>(x + 3) });
	/// assert_eq!(future.await, Ok(4));
	/// # });
	/// ```
	///
	/// Calling [`and_then`](TryFutureExt::and_then) on an errored future has no
	/// effect:
	///
	/// ```
	/// use futures::future::TryFutureExt;
	///
	/// # futures::executor::block_on(async {
	/// let future = async { Err::<i32, i32>(1) };
	/// let future = future.and_then(\|x\| async move { Err::<i32, i32>(x + 3) });
	/// assert_eq!(future.await, Err(1));
	/// # });
	/// ```
	fn and_then<Fut, F>(self, f: F) -> AndThen<Self, Fut, F>
	where
	F: FnOnce(Self::Ok) -> Fut,
	Fut: TryFuture<Error = Self::Error>,
	Self: Sized,
	{
	assert_future::<Result<Fut::Ok, Fut::Error>, _>(AndThen::new(self, f))
	}

	/// Executes another future if this one resolves to an error. The
	/// error value is passed to a closure to create this subsequent future.
	///
	/// The provided closure `f` will only be called if this future is resolved
	/// to an [`Err`]. If this future resolves to an [`Ok`], panics, or is
	/// dropped, then the provided closure will never be invoked. The
	/// [`Ok`](TryFuture::Ok) type of this future and the future returned by `f`
	/// have to match.
	///
	/// Note that this method consumes the future it is called on and returns a
	/// wrapped version of it.
	///
	/// # Examples
	///
	/// ```
	/// use futures::future::TryFutureExt;
	///
	/// # futures::executor::block_on(async {
	/// let future = async { Err::<i32, i32>(1) };
	/// let future = future.or_else(\|x\| async move { Err::<i32, i32>(x + 3) });
	/// assert_eq!(future.await, Err(4));
	/// # });
	/// ```
	///
	/// Calling [`or_else`](TryFutureExt::or_else) on a successful future has
	/// no effect:
	///
	/// ```
	/// use futures::future::TryFutureExt;
	///
	/// # futures::executor::block_on(async {
	/// let future = async { Ok::<i32, i32>(1) };
	/// let future = future.or_else(\|x\| async move { Ok::<i32, i32>(x + 3) });
	/// assert_eq!(future.await, Ok(1));
	/// # });
	/// ```
	fn or_else<Fut, F>(self, f: F) -> OrElse<Self, Fut, F>
	where
	F: FnOnce(Self::Error) -> Fut,
	Fut: TryFuture<Ok = Self::Ok>,
	Self: Sized,
	{
	assert_future::<Result<Fut::Ok, Fut::Error>, _>(OrElse::new(self, f))
	}

	/// Do something with the success value of a future before passing it on.
	///
	/// When using futures, you'll often chain several of them together. While
	/// working on such code, you might want to check out what's happening at
	/// various parts in the pipeline, without consuming the intermediate
	/// value. To do that, insert a call to `inspect_ok`.
	///
	/// # Examples
	///
	/// ```
	/// # futures::executor::block_on(async {
	/// use futures::future::TryFutureExt;
	///
	/// let future = async { Ok::<_, ()>(1) };
	/// let new_future = future.inspect_ok(\|&x\| println!("about to resolve: {}", x));
	/// assert_eq!(new_future.await, Ok(1));
	/// # });
	/// ```
	fn inspect_ok<F>(self, f: F) -> InspectOk<Self, F>
	where
	F: FnOnce(&Self::Ok),
	Self: Sized,
	{
	assert_future::<Result<Self::Ok, Self::Error>, _>(InspectOk::new(self, f))
	}

	/// Do something with the error value of a future before passing it on.
	///
	/// When using futures, you'll often chain several of them together. While
	/// working on such code, you might want to check out what's happening at
	/// various parts in the pipeline, without consuming the intermediate
	/// value. To do that, insert a call to `inspect_err`.
	///
	/// # Examples
	///
	/// ```
	/// # futures::executor::block_on(async {
	/// use futures::future::TryFutureExt;
	///
	/// let future = async { Err::<(), _>(1) };
	/// let new_future = future.inspect_err(\|&x\| println!("about to error: {}", x));
	/// assert_eq!(new_future.await, Err(1));
	/// # });
	/// ```
	fn inspect_err<F>(self, f: F) -> InspectErr<Self, F>
	where
	F: FnOnce(&Self::Error),
	Self: Sized,
	{
	assert_future::<Result<Self::Ok, Self::Error>, _>(InspectErr::new(self, f))
	}

	/// Flatten the execution of this future when the successful result of this
	/// future is another future.
	///
	/// This is equivalent to `future.and_then(\|x\| x)`.
	fn try_flatten(self) -> TryFlatten<Self, Self::Ok>
	where
	Self::Ok: TryFuture<Error = Self::Error>,
	Self: Sized,
	{
	TryFlatten::new(self)
	}

	/// Flatten the execution of this future when the successful result of this
	/// future is a stream.
	///
	/// This can be useful when stream initialization is deferred, and it is
	/// convenient to work with that stream as if stream was available at the
	/// call site.
	///
	/// Note that this function consumes this future and returns a wrapped
	/// version of it.
	///
	/// # Examples
	///
	/// ```
	/// # futures::executor::block_on(async {
	/// use futures::future::TryFutureExt;
	/// use futures::stream::{self, TryStreamExt};
	///
	/// let stream_items = vec![17, 18, 19].into_iter().map(Ok);
	/// let future_of_a_stream = async { Ok::<_, ()>(stream::iter(stream_items)) };
	///
	/// let stream = future_of_a_stream.try_flatten_stream();
	/// let list = stream.try_collect::<Vec<_>>().await;
	/// assert_eq!(list, Ok(vec![17, 18, 19]));
	/// # });
	/// ```
	fn try_flatten_stream(self) -> TryFlattenStream<Self>
	where
	Self::Ok: TryStream<Error = Self::Error>,
	Self: Sized,
	{
	TryFlattenStream::new(self)
	}

	/// Unwraps this future's ouput, producing a future with this future's
	/// [`Ok`](TryFuture::Ok) type as its
	/// [`Output`](std::future::Future::Output) type.
	///
	/// If this future is resolved successfully, the returned future will
	/// contain the original future's success value as output. Otherwise, the
	/// closure `f` is called with the error value to produce an alternate
	/// success value.
	///
	/// This method is similar to the [`Result::unwrap_or_else`] method.
	///
	/// # Examples
	///
	/// ```
	/// use futures::future::TryFutureExt;
	///
	/// # futures::executor::block_on(async {
	/// let future = async { Err::<(), &str>("Boom!") };
	/// let future = future.unwrap_or_else(\|_\| ());
	/// assert_eq!(future.await, ());
	/// # });
	/// ```
	fn unwrap_or_else<F>(self, f: F) -> UnwrapOrElse<Self, F>
	where
	Self: Sized,
	F: FnOnce(Self::Error) -> Self::Ok,
	{
	assert_future::<Self::Ok, _>(UnwrapOrElse::new(self, f))
	}

	/// Wraps a [`TryFuture`] into a future compatable with libraries using
	/// futures 0.1 future definitons. Requires the `compat` feature to enable.
	#[cfg(feature = "compat")]
	fn compat(self) -> Compat<Self>
	where
	Self: Sized + Unpin,
	{
	Compat::new(self)
	}

	/// Wraps a [`TryFuture`] into a type that implements
	/// [`Future`](std::future::Future).
	///
	/// [`TryFuture`]s currently do not implement the
	/// [`Future`](std::future::Future) trait due to limitations of the
	/// compiler.
	///
	/// # Examples
	///
	/// ```
	/// use futures::future::{Future, TryFuture, TryFutureExt};
	///
	/// # type T = i32;
	/// # type E = ();
	/// fn make_try_future() -> impl TryFuture<Ok = T, Error = E> { // ... }
	/// # async { Ok::<i32, ()>(1) }
	/// # }
	/// fn take_future(future: impl Future<Output = Result<T, E>>) { /* ... */ }
	///
	/// take_future(make_try_future().into_future());
	/// ```
	fn into_future(self) -> IntoFuture<Self>
	where
	Self: Sized,
	{
	IntoFuture::new(self)
	}

	/// A convenience method for calling [`TryFuture::try_poll`] on [`Unpin`]
	/// future types.
	fn try_poll_unpin(&mut self, cx: &mut Context<'_>) -> Poll<Result<Self::Ok, Self::Error>>
	where
	Self: Unpin,
	{
	Pin::new(self).try_poll(cx)
	}
	}