refactor: TryFutures are Futures now, into_future is no longer need

.github/workflows/ci.yml

@@ -78,7 +78,7 @@ jobs:
         rust:
           # This is the minimum Rust version supported by futures-core, futures-io, futures-sink.
           # When updating this, the reminder to update the minimum required version in README.md and Cargo.toml.
-          - '1.36'
+          - '1.52'
     runs-on: ubuntu-latest
     timeout-minutes: 60
     steps:
@@ -91,7 +91,9 @@ jobs:
           tool: rust@${{ matrix.rust }},cargo-hack
           fallback: none
       # remove dev-dependencies to avoid https://github.com/rust-lang/cargo/issues/4866
-      - run: cargo hack --remove-dev-deps --workspace
+      - run: |
+          cargo hack --remove-dev-deps --workspace \
+            --exclude futures --exclude futures-util --exclude futures-task --exclude futures-macro --exclude futures-executor --exclude futures-channel --exclude futures-test
       # Check no-default-features
       - run: |
           cargo hack build --workspace --ignore-private --no-default-features \

futures-core/Cargo.toml

@@ -3,7 +3,7 @@ name = "futures-core"
 version = "1.0.0-alpha.0"
 edition = "2018"
 # NB: Sync with "Usage" section in README.md and core-msrv job in .github/workflows/ci.yml
-rust-version = "1.36"
+rust-version = "1.52"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/rust-lang/futures-rs"
 homepage = "https://rust-lang.github.io/futures-rs"

futures-core/README.md

@@ -11,7 +11,7 @@ Add this to your `Cargo.toml`:
 futures-core = "0.3"
 ```
 
-The current `futures-core` requires Rust 1.36 or later.
+The current `futures-core` requires Rust 1.52 or later.
 
 ## License
 

futures-core/src/future.rs

@@ -2,11 +2,7 @@
 
 #[doc(no_inline)]
 pub use core::future::Future;
-use core::{
-    ops::DerefMut,
-    pin::Pin,
-    task::{Context, Poll},
-};
+use core::{ops::DerefMut, pin::Pin};
 
 /// An owned dynamically typed [`Future`] for use in cases where you can't
 /// statically type your result or need to add some indirection.
@@ -31,10 +27,10 @@ pub type LocalBoxFuture<'a, T> = Pin<alloc::boxed::Box<dyn Future<Output = T> +
 /// should no longer be polled.
 ///
 /// `is_terminated` will return `true` if a future should no longer be polled.
-/// Usually, this state occurs after `poll` (or `try_poll`) returned
-/// `Poll::Ready`. However, `is_terminated` may also return `true` if a future
-/// has become inactive and can no longer make progress and should be ignored
-/// or dropped rather than being `poll`ed again.
+/// Usually, this state occurs after `poll` returned `Poll::Ready`. However,
+/// `is_terminated` may also return `true` if a future has become inactive
+/// and can no longer make progress and should be ignored or dropped rather
+/// than being `poll`ed again.
 pub trait FusedFuture: Future {
     /// Returns `true` if the underlying future should no longer be polled.
     fn is_terminated(&self) -> bool;
@@ -56,29 +52,14 @@ where
     }
 }
 
-mod private_try_future {
-    use super::Future;
-
-    pub trait Sealed {}
-
-    impl<F, T, E> Sealed for F where F: ?Sized + Future<Output = Result<T, E>> {}
-}
-
 /// A convenience for futures that return `Result` values that includes
 /// a variety of adapters tailored to such futures.
-pub trait TryFuture: Future + private_try_future::Sealed {
+pub trait TryFuture: Future<Output = Result<Self::Ok, Self::Error>> {
     /// The type of successful values yielded by this future
     type Ok;
 
     /// The type of failures yielded by this future
     type Error;
-
-    /// Poll this `TryFuture` as if it were a `Future`.
-    ///
-    /// This method is a stopgap for a compiler limitation that prevents us from
-    /// directly inheriting from the `Future` trait; in the future it won't be
-    /// needed.
-    fn try_poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<Self::Ok, Self::Error>>;
 }
 
 impl<F, T, E> TryFuture for F
@@ -87,11 +68,6 @@ where
 {
     type Ok = T;
     type Error = E;
-
-    #[inline]
-    fn try_poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-        self.poll(cx)
-    }
 }
 
 #[cfg(feature = "alloc")]
@@ -105,11 +81,10 @@ mod if_alloc {
             <F as FusedFuture>::is_terminated(&**self)
         }
     }
+}
 
-    #[cfg(feature = "std")]
-    impl<F: FusedFuture> FusedFuture for std::panic::AssertUnwindSafe<F> {
-        fn is_terminated(&self) -> bool {
-            <F as FusedFuture>::is_terminated(&**self)
-        }
+impl<F: FusedFuture> FusedFuture for core::panic::AssertUnwindSafe<F> {
+    fn is_terminated(&self) -> bool {
+        <F as FusedFuture>::is_terminated(&**self)
     }
 }

futures-core/src/stream.rs

@@ -141,7 +141,7 @@ where
 /// should no longer be polled.
 ///
 /// `is_terminated` will return `true` if a future should no longer be polled.
-/// Usually, this state occurs after `poll_next` (or `try_poll_next`) returned
+/// Usually, this state occurs after `poll_next` returned
 /// `Poll::Ready(None)`. However, `is_terminated` may also return `true` if a
 /// stream has become inactive and can no longer make progress and should be
 /// ignored or dropped rather than being polled again.
@@ -166,32 +166,14 @@ where
     }
 }
 
-mod private_try_stream {
-    use super::Stream;
-
-    pub trait Sealed {}
-
-    impl<S, T, E> Sealed for S where S: ?Sized + Stream<Item = Result<T, E>> {}
-}
-
 /// A convenience for streams that return `Result` values that includes
 /// a variety of adapters tailored to such futures.
-pub trait TryStream: Stream + private_try_stream::Sealed {
+pub trait TryStream: Stream<Item = Result<Self::Ok, Self::Error>> {
     /// The type of successful values yielded by this future
     type Ok;
 
     /// The type of failures yielded by this future
     type Error;
-
-    /// Poll this `TryStream` as if it were a `Stream`.
-    ///
-    /// This method is a stopgap for a compiler limitation that prevents us from
-    /// directly inheriting from the `Stream` trait; in the future it won't be
-    /// needed.
-    fn try_poll_next(
-        self: Pin<&mut Self>,
-        cx: &mut Context<'_>,
-    ) -> Poll<Option<Result<Self::Ok, Self::Error>>>;
 }
 
 impl<S, T, E> TryStream for S
@@ -200,13 +182,6 @@ where
 {
     type Ok = T;
     type Error = E;
-
-    fn try_poll_next(
-        self: Pin<&mut Self>,
-        cx: &mut Context<'_>,
-    ) -> Poll<Option<Result<Self::Ok, Self::Error>>> {
-        self.poll_next(cx)
-    }
 }
 
 #[cfg(feature = "alloc")]
@@ -227,22 +202,21 @@ mod if_alloc {
         }
     }
 
-    #[cfg(feature = "std")]
-    impl<S: Stream> Stream for std::panic::AssertUnwindSafe<S> {
-        type Item = S::Item;
-
-        fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<S::Item>> {
-            unsafe { self.map_unchecked_mut(|x| &mut x.0) }.poll_next(cx)
-        }
-
-        fn size_hint(&self) -> (usize, Option<usize>) {
-            self.0.size_hint()
-        }
-    }
-
     impl<S: ?Sized + FusedStream + Unpin> FusedStream for Box<S> {
         fn is_terminated(&self) -> bool {
             <S as FusedStream>::is_terminated(&**self)
         }
     }
 }
+
+impl<S: Stream> Stream for core::panic::AssertUnwindSafe<S> {
+    type Item = S::Item;
+
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<S::Item>> {
+        unsafe { self.map_unchecked_mut(|x| &mut x.0) }.poll_next(cx)
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.0.size_hint()
+    }
+}

futures-io/Cargo.toml

@@ -3,7 +3,7 @@ name = "futures-io"
 version = "0.3.33"
 edition = "2018"
 # NB: Sync with "Usage" section in README.md and core-msrv job in .github/workflows/ci.yml
-rust-version = "1.36"
+rust-version = "1.52"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/rust-lang/futures-rs"
 homepage = "https://rust-lang.github.io/futures-rs"

futures-io/README.md

@@ -11,7 +11,7 @@ Add this to your `Cargo.toml`:
 futures-io = "0.3"
 ```
 
-The current `futures-io` requires Rust 1.36 or later.
+The current `futures-io` requires Rust 1.52 or later.
 
 ## License
 

futures-sink/Cargo.toml

@@ -3,7 +3,7 @@ name = "futures-sink"
 version = "0.4.0-alpha.0"
 edition = "2018"
 # NB: Sync with "Usage" section in README.md and core-msrv job in .github/workflows/ci.yml
-rust-version = "1.36"
+rust-version = "1.52"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/rust-lang/futures-rs"
 homepage = "https://rust-lang.github.io/futures-rs"

futures-sink/README.md

@@ -11,7 +11,7 @@ Add this to your `Cargo.toml`:
 futures-sink = "0.3"
 ```
 
-The current `futures-sink` requires Rust 1.36 or later.
+The current `futures-sink` requires Rust 1.52 or later.
 
 ## License
 

futures-util/src/compat/compat03as01.rs

@@ -106,7 +106,7 @@ where
     type Error = Fut::Error;
 
     fn poll(&mut self) -> Poll01<Self::Item, Self::Error> {
-        with_context(self, |inner, cx| poll_03_to_01(inner.try_poll(cx)))
+        with_context(self, |inner, cx| poll_03_to_01(inner.poll(cx)))
     }
 }
 
@@ -118,7 +118,7 @@ where
     type Error = St::Error;
 
     fn poll(&mut self) -> Poll01<Option<Self::Item>, Self::Error> {
-        with_context(self, |inner, cx| match inner.try_poll_next(cx)? {
+        with_context(self, |inner, cx| match inner.poll_next(cx)? {
             task03::Poll::Ready(None) => Ok(Async01::Ready(None)),
             task03::Poll::Ready(Some(t)) => Ok(Async01::Ready(Some(t))),
             task03::Poll::Pending => Ok(Async01::NotReady),

futures-util/src/future/mod.rs

@@ -39,8 +39,8 @@ mod try_future;
 #[cfg_attr(docsrs, doc(cfg(feature = "sink")))]
 pub use self::try_future::FlattenSink;
 pub use self::try_future::{
-    AndThen, ErrInto, InspectErr, InspectOk, IntoFuture, MapErr, MapOk, MapOkOrElse, OkInto,
-    OrElse, TryFlatten, TryFlattenStream, TryFutureExt, UnwrapOrElse,
+    AndThen, ErrInto, InspectErr, InspectOk, MapErr, MapOk, MapOkOrElse, OkInto, OrElse,
+    TryFlatten, TryFlattenStream, TryFutureExt, UnwrapOrElse,
 };
 
 // Primitive futures

futures-util/src/future/select_ok.rs

@@ -7,7 +7,7 @@ use futures_core::{
 };
 
 use super::assert_future;
-use crate::future::TryFutureExt;
+use crate::future::FutureExt;
 
 /// Future for the [`select_ok`] function.
 #[derive(Debug)]
@@ -51,7 +51,7 @@ impl<Fut: TryFuture + Unpin> Future for SelectOk<Fut> {
         // loop until we've either exhausted all errors, a success was hit, or nothing is ready
         loop {
             let item =
-                self.inner.iter_mut().enumerate().find_map(|(i, f)| match f.try_poll_unpin(cx) {
+                self.inner.iter_mut().enumerate().find_map(|(i, f)| match f.poll_unpin(cx) {
                     Poll::Pending => None,
                     Poll::Ready(e) => Some((i, e)),
                 });