Change StreamExt::boxed to return BoxStream and add StreamExt::boxed_local

Author: taiki-e

futures-core/src/future/mod.rs

@@ -9,13 +9,13 @@ pub use core::future::Future;
 mod future_obj;
 pub use self::future_obj::{FutureObj, LocalFutureObj, UnsafeFutureObj};
 
-#[cfg(feature = "alloc")]
 /// An owned dynamically typed [`Future`] for use in cases where you can't
 /// statically type your result or need to add some indirection.
+#[cfg(feature = "alloc")]
 pub type BoxFuture<'a, T> = Pin<alloc::boxed::Box<dyn Future<Output = T> + Send + 'a>>;
 
-#[cfg(feature = "alloc")]
 /// `BoxFuture`, but without the `Send` requirement.
+#[cfg(feature = "alloc")]
 pub type LocalBoxFuture<'a, T> = Pin<alloc::boxed::Box<dyn Future<Output = T> + 'a>>;
 
 /// A `Future` or `TryFuture` which tracks whether or not the underlying future

futures-core/src/stream.rs

@@ -4,11 +4,15 @@ use core::ops::DerefMut;
 use core::pin::Pin;
 use core::task::{Context, Poll};
 
-#[cfg(feature = "alloc")]
 /// An owned dynamically typed [`Stream`] for use in cases where you can't
 /// statically type your result or need to add some indirection.
+#[cfg(feature = "alloc")]
 pub type BoxStream<'a, T> = Pin<alloc::boxed::Box<dyn Stream<Item = T> + Send + 'a>>;
 
+/// `BoxStream`, but without the `Send` requirement.
+#[cfg(feature = "alloc")]
+pub type LocalBoxStream<'a, T> = Pin<alloc::boxed::Box<dyn Stream<Item = T> + 'a>>;
+
 /// A stream of values produced asynchronously.
 ///
 /// If `Future<Output = T>` is an asynchronous version of `T`, then `Stream<Item

futures-util/src/future/mod.rs

@@ -492,6 +492,9 @@ pub trait FutureExt: Future {
     }
 
     /// Wrap the future in a Box, pinning it.
+    ///
+    /// This method is only available when the `std` or `alloc` feature of this
+    /// library is activated, and it is activated by default.
     #[cfg(feature = "alloc")]
     fn boxed<'a>(self) -> BoxFuture<'a, Self::Output>
         where Self: Sized + Send + 'a
@@ -502,6 +505,9 @@ pub trait FutureExt: Future {
     /// Wrap the future in a Box, pinning it.
     ///
     /// Similar to `boxed`, but without the `Send` requirement.
+    ///
+    /// This method is only available when the `std` or `alloc` feature of this
+    /// library is activated, and it is activated by default.
     #[cfg(feature = "alloc")]
     fn boxed_local<'a>(self) -> LocalBoxFuture<'a, Self::Output>
         where Self: Sized + 'a

futures-util/src/stream/mod.rs

@@ -3,6 +3,7 @@
 //! This module contains a number of functions for working with `Stream`s,
 //! including the `StreamExt` trait which adds methods to `Stream` types.
 
+use crate::future::Either;
 use core::pin::Pin;
 use futures_core::future::Future;
 use futures_core::stream::{FusedStream, Stream};
@@ -13,7 +14,8 @@ use futures_core::task::{Context, Poll};
 use futures_sink::Sink;
 #[cfg(feature = "alloc")]
 use alloc::boxed::Box;
-use crate::future::Either;
+#[cfg(feature = "alloc")]
+use futures_core::stream::{BoxStream, LocalBoxStream};
 
 mod iter;
 pub use self::iter::{iter, Iter};
@@ -894,8 +896,21 @@ pub trait StreamExt: Stream {
     /// This method is only available when the `std` or `alloc` feature of this
     /// library is activated, and it is activated by default.
     #[cfg(feature = "alloc")]
-    fn boxed(self) -> Pin<Box<Self>>
-        where Self: Sized
+    fn boxed<'a>(self) -> BoxStream<'a, Self::Item>
+        where Self: Sized + Send + 'a
+    {
+        Box::pin(self)
+    }
+
+    /// Wrap the stream in a Box, pinning it.
+    ///
+    /// Similar to `boxed`, but without the `Send` requirement.
+    ///
+    /// This method is only available when the `std` or `alloc` feature of this
+    /// library is activated, and it is activated by default.
+    #[cfg(feature = "alloc")]
+    fn boxed_local<'a>(self) -> LocalBoxStream<'a, Self::Item>
+        where Self: Sized + 'a
     {
         Box::pin(self)
     }

futures/src/lib.rs

@@ -213,7 +213,7 @@ pub mod future {
     };
 
     #[cfg(feature = "alloc")]
-    pub use futures_core::future::BoxFuture;
+    pub use futures_core::future::{BoxFuture, LocalBoxFuture};
 
     pub use futures_util::future::{
         lazy, Lazy,
@@ -398,7 +398,7 @@ pub mod stream {
     };
 
     #[cfg(feature = "alloc")]
-    pub use futures_core::stream::BoxStream;
+    pub use futures_core::stream::{BoxStream, LocalBoxStream};
 
     pub use futures_util::stream::{
         iter, Iter,