Merge branch 'master' into add_stdin_lock

.github/workflows/ci.yml

@@ -7,12 +7,13 @@ on:
       - staging
       - trying
 
+env:
+  RUSTFLAGS: -Dwarnings
+
 jobs:
   build_and_test:
     name: Build and test
     runs-on: ${{ matrix.os }}
-    env:
-      RUSTFLAGS: -Dwarnings
     strategy:
       matrix:
         os: [ubuntu-latest, windows-latest, macOS-latest]
@@ -48,8 +49,6 @@ jobs:
   check_fmt_and_docs:
     name: Checking fmt and docs
     runs-on: ubuntu-latest
-    env:
-      RUSTFLAGS: -Dwarnings
     steps:
     - uses: actions/checkout@master
 
@@ -81,20 +80,11 @@ jobs:
   clippy_check:
     name: Clippy check
     runs-on: ubuntu-latest
-    # TODO: There is a lot of warnings
-    # env:
-    #   RUSTFLAGS: -Dwarnings
     steps:
       - uses: actions/checkout@v1
-      - id: component
+      - name: Install rust
-        uses: actions-rs/components-nightly@v1
+        run: rustup update beta && rustup default beta
-        with:
+      - name: Install clippy
-          component: clippy
+        run: rustup component add clippy
-      - uses: actions-rs/toolchain@v1
+      - name: clippy
-        with:
+        run: cargo clippy --all --features unstable
-            toolchain: ${{ steps.component.outputs.toolchain }}
-            override: true
-      - run: rustup component add clippy
-      - uses: actions-rs/clippy-check@v1
-        with:
-          token: ${{ secrets.GITHUB_TOKEN }}

Cargo.toml

@@ -9,7 +9,7 @@ authors = [
 edition = "2018"
 license = "Apache-2.0/MIT"
 repository = "https://github.com/async-rs/async-std"
-homepage = "https://github.com/async-rs/async-std"
+homepage = "https://async.rs"
 documentation = "https://docs.rs/async-std"
 description = "Async version of the Rust standard library"
 keywords = ["async", "await", "future", "std", "task"]

docs/src/concepts/futures.md

@@ -24,11 +24,7 @@ To sum up: Rust gives us the ability to safely abstract over important propertie
 
 ## An easy view of computation
 
-While computation is a subject to write a whole [book](https://computationbook.com/) about, a very simplified view suffices for us:
+While computation is a subject to write a whole [book](https://computationbook.com/) about, a very simplified view suffices for us: A sequence of composable operations which can branch based on a decision, run to succession and yield a result or yield an error
-
-- computation is a sequence of composable operations
-- they can branch based on a decision
-- they either run to succession and yield a result, or they can yield an error
 
 ## Deferring computation
 
@@ -136,11 +132,11 @@ When executing 2 or more of these functions at the same time, our runtime system
 
 ## Conclusion
 
-Working from values, we searched for something that expresses *working towards a value available sometime later*. From there, we talked about the concept of polling.
+Working from values, we searched for something that expresses *working towards a value available later*. From there, we talked about the concept of polling.
 
 A `Future` is any data type that does not represent a value, but the ability to *produce a value at some point in the future*. Implementations of this are very varied and detailed depending on use-case, but the interface is simple.
 
-Next, we will introduce you to `tasks`, which we need to actually *run* Futures.
+Next, we will introduce you to `tasks`, which we will use to actually *run* Futures.
 
 [^1]: Two parties reading while it is guaranteed that no one is writing is always safe.
 

docs/src/concepts/tasks.md

@@ -80,7 +80,7 @@ Tasks in `async_std` are one of the core abstractions. Much like Rust's `thread`
 
 ## Blocking
 
-`Task`s are assumed to run _concurrently_, potentially by sharing a thread of execution. This means that operations blocking an _operating system thread_, such as `std::thread::sleep` or io function from Rust's `std` library will _stop execution of all tasks sharing this thread_. Other libraries (such as database drivers) have similar behaviour. Note that _blocking the current thread_ is not in and by itself bad behaviour, just something that does not mix well with the concurrent execution model of `async-std`. Essentially, never do this:
+`Task`s are assumed to run _concurrently_, potentially by sharing a thread of execution. This means that operations blocking an _operating system thread_, such as `std::thread::sleep` or io function from Rust's `std` library will _stop execution of all tasks sharing this thread_. Other libraries (such as database drivers) have similar behaviour. Note that _blocking the current thread_ is not in and of itself bad behaviour, just something that does not mix well with the concurrent execution model of `async-std`. Essentially, never do this:
 
 ```rust,edition2018
 # extern crate async_std;

docs/src/overview/async-std.md

@@ -4,4 +4,4 @@
 
 `async-std` provides an interface to all important primitives: filesystem operations, network operations and concurrency basics like timers. It also exposes a `task` in a model similar to the `thread` module found in the Rust standard lib.  But it does not only include I/O primitives, but also `async/await` compatible versions of primitives like `Mutex`.
 
-[organization]: https://github.com/async-rs/async-std
+[organization]: https://github.com/async-rs

docs/src/overview/stability-guarantees.md

@@ -31,7 +31,7 @@ In general, this crate will be conservative with respect to the minimum supporte
 
 ## Security fixes
 
-Security fixes will be applied to _all_ minor branches of this library in all _supported_ major revisions. This policy might change in the future, in which case we give at least _3 month_ of ahead notice.
+Security fixes will be applied to _all_ minor branches of this library in all _supported_ major revisions. This policy might change in the future, in which case we give a notice at least _3 months_ ahead.
 
 ## Credits
 

examples/a-chat/main.rs

@@ -8,6 +8,6 @@ fn main() -> Result<()> {
     match (args.nth(1).as_ref().map(String::as_str), args.next()) {
         (Some("client"), None) => client::main(),
         (Some("server"), None) => server::main(),
-        _ => Err("Usage: a-chat [client|server]")?,
+        _ => Err("Usage: a-chat [client|server]".into()),
     }
 }

examples/a-chat/server.rs

@@ -45,7 +45,7 @@ async fn connection_loop(mut broker: Sender<Event>, stream: TcpStream) -> Result
     let mut lines = reader.lines();
 
     let name = match lines.next().await {
-        None => Err("peer disconnected immediately")?,
+        None => return Err("peer disconnected immediately".into()),
         Some(line) => line?,
     };
     let (_shutdown_sender, shutdown_receiver) = mpsc::unbounded::<Void>();

src/fs/file.rs

@@ -66,6 +66,23 @@ pub struct File {
 }
 
 impl File {
+    /// Creates an async file handle.
+    pub(crate) fn new(file: std::fs::File, is_flushed: bool) -> File {
+        let file = Arc::new(file);
+
+        File {
+            file: file.clone(),
+            lock: Lock::new(State {
+                file,
+                mode: Mode::Idle,
+                cache: Vec::new(),
+                is_flushed,
+                last_read_err: None,
+                last_write_err: None,
+            }),
+        }
+    }
+
     /// Opens a file in read-only mode.
     ///
     /// See the [`OpenOptions::open`] function for more options.
@@ -96,7 +113,7 @@ impl File {
     pub async fn open<P: AsRef<Path>>(path: P) -> io::Result<File> {
         let path = path.as_ref().to_owned();
         let file = blocking::spawn(move || std::fs::File::open(&path)).await?;
-        Ok(file.into())
+        Ok(File::new(file, true))
     }
 
     /// Opens a file in write-only mode.
@@ -131,7 +148,7 @@ impl File {
     pub async fn create<P: AsRef<Path>>(path: P) -> io::Result<File> {
         let path = path.as_ref().to_owned();
         let file = blocking::spawn(move || std::fs::File::create(&path)).await?;
-        Ok(file.into())
+        Ok(File::new(file, true))
     }
 
     /// Synchronizes OS-internal buffered contents and metadata to disk.
@@ -383,19 +400,7 @@ impl Seek for &File {
 
 impl From<std::fs::File> for File {
     fn from(file: std::fs::File) -> File {
-        let file = Arc::new(file);
+        File::new(file, false)
-
-        File {
-            file: file.clone(),
-            lock: Lock::new(State {
-                file,
-                mode: Mode::Idle,
-                cache: Vec::new(),
-                is_flushed: false,
-                last_read_err: None,
-                last_write_err: None,
-            }),
-        }
     }
 }
 

src/fs/open_options.rs

@@ -284,7 +284,10 @@ impl OpenOptions {
     pub fn open<P: AsRef<Path>>(&self, path: P) -> impl Future<Output = io::Result<File>> {
         let path = path.as_ref().to_owned();
         let options = self.0.clone();
-        async move { blocking::spawn(move || options.open(path).map(|f| f.into())).await }
+        async move {
+            let file = blocking::spawn(move || options.open(path)).await?;
+            Ok(File::new(file, true))
+        }
     }
 }
 

src/future/future.rs

@@ -1,3 +1,11 @@
+cfg_unstable! {
+    mod delay;
+
+    use std::time::Duration;
+
+    use delay::DelayFuture;
+}
+
 extension_trait! {
     use std::pin::Pin;
     use std::ops::{Deref, DerefMut};
@@ -99,6 +107,28 @@ extension_trait! {
     }
 
     pub trait FutureExt: std::future::Future {
+        /// Returns a Future that delays execution for a specified time.
+        ///
+        /// # Examples
+        ///
+        /// ```
+        /// # async_std::task::block_on(async {
+        /// use async_std::prelude::*;
+        /// use async_std::future;
+        /// use std::time::Duration;
+        ///
+        /// let a = future::ready(1).delay(Duration::from_millis(2000));
+        /// dbg!(a.await);
+        /// # })
+        /// ```
+        #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
+        #[cfg(any(feature = "unstable", feature = "docs"))]
+        fn delay(self, dur: Duration) -> impl Future<Output = Self::Output> [DelayFuture<Self>]
+        where
+            Self: Future + Sized
+        {
+            DelayFuture::new(self, dur)
+        }
     }
 
     impl<F: Future + Unpin + ?Sized> Future for Box<F> {

src/future/future/delay.rs

@@ -0,0 +1,43 @@
+use std::pin::Pin;
+use std::time::Duration;
+
+use futures_timer::Delay;
+use pin_project_lite::pin_project;
+
+use crate::future::Future;
+use crate::task::{Context, Poll};
+
+pin_project! {
+    #[doc(hidden)]
+    #[derive(Debug)]
+    pub struct DelayFuture<F> {
+        #[pin]
+        future: F,
+        #[pin]
+        delay: Delay,
+    }
+}
+
+impl<F> DelayFuture<F> {
+    pub fn new(future: F, dur: Duration) -> DelayFuture<F> {
+        let delay = Delay::new(dur);
+
+        DelayFuture { future, delay }
+    }
+}
+
+impl<F: Future> Future for DelayFuture<F> {
+    type Output = F::Output;
+
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let this = self.project();
+
+        match this.delay.poll(cx) {
+            Poll::Pending => Poll::Pending,
+            Poll::Ready(_) => match this.future.poll(cx) {
+                Poll::Ready(v) => Poll::Ready(v),
+                Poll::Pending => Poll::Pending,
+            },
+        }
+    }
+}

src/io/empty.rs

@@ -28,9 +28,10 @@ pub fn empty() -> Empty {
 
 /// A reader that contains no data.
 ///
-/// This reader is constructed by the [`sink`] function.
+/// This reader is created by the [`empty`] function. See its
+/// documentation for more.
 ///
-/// [`sink`]: fn.sink.html
+/// [`empty`]: fn.empty.html
 pub struct Empty {
     _private: (),
 }

src/io/repeat.rs

@@ -29,7 +29,8 @@ pub fn repeat(byte: u8) -> Repeat {
 
 /// A reader which yields one byte over and over and over and over and over and...
 ///
-/// This reader is constructed by the [`repeat`] function.
+/// This reader is created by the [`repeat`] function. See its
+/// documentation for more.
 ///
 /// [`repeat`]: fn.repeat.html
 pub struct Repeat {

src/io/sink.rs

@@ -25,7 +25,8 @@ pub fn sink() -> Sink {
 
 /// A writer that consumes and drops all data.
 ///
-/// This writer is constructed by the [`sink`] function.
+/// This writer is constructed by the [`sink`] function. See its documentation
+/// for more.
 ///
 /// [`sink`]: fn.sink.html
 pub struct Sink {

src/io/stderr.rs

@@ -12,6 +12,12 @@ use crate::task::{blocking, Context, JoinHandle, Poll};
 ///
 /// [`std::io::stderr`]: https://doc.rust-lang.org/std/io/fn.stderr.html
 ///
+/// ### Note: Windows Portability Consideration
+///
+/// When operating in a console, the Windows implementation of this stream does not support
+/// non-UTF-8 byte sequences. Attempting to write bytes that are not valid UTF-8 will return
+/// an error.
+///
 /// # Examples
 ///
 /// ```no_run
@@ -35,12 +41,16 @@ pub fn stderr() -> Stderr {
 
 /// A handle to the standard error of the current process.
 ///
-/// Created by the [`stderr`] function.
+/// This writer is created by the [`stderr`] function. See its documentation for
+/// more.
+///
+/// ### Note: Windows Portability Consideration
 ///
-/// This type is an async version of [`std::io::Stderr`].
+/// When operating in a console, the Windows implementation of this stream does not support
+/// non-UTF-8 byte sequences. Attempting to write bytes that are not valid UTF-8 will return
+/// an error.
 ///
 /// [`stderr`]: fn.stderr.html
-/// [`std::io::Stderr`]: https://doc.rust-lang.org/std/io/struct.Stderr.html
 #[derive(Debug)]
 pub struct Stderr(Mutex<State>);
 

src/io/stdin.rs

@@ -12,6 +12,12 @@ use crate::task::{blocking, Context, JoinHandle, Poll};
 ///
 /// [`std::io::stdin`]: https://doc.rust-lang.org/std/io/fn.stdin.html
 ///
+/// ### Note: Windows Portability Consideration
+///
+/// When operating in a console, the Windows implementation of this stream does not support
+/// non-UTF-8 byte sequences. Attempting to write bytes that are not valid UTF-8 will return
+/// an error.
+///
 /// # Examples
 ///
 /// ```no_run
@@ -36,12 +42,16 @@ pub fn stdin() -> Stdin {
 
 /// A handle to the standard input of the current process.
 ///
-/// Created by the [`stdin`] function.
+/// This reader is created by the [`stdin`] function. See its documentation for
+/// more.
+///
+/// ### Note: Windows Portability Consideration
 ///
-/// This type is an async version of [`std::io::Stdin`].
+/// When operating in a console, the Windows implementation of this stream does not support
+/// non-UTF-8 byte sequences. Attempting to write bytes that are not valid UTF-8 will return
+/// an error.
 ///
 /// [`stdin`]: fn.stdin.html
-/// [`std::io::Stdin`]: https://doc.rust-lang.org/std/io/struct.Stdin.html
 #[derive(Debug)]
 pub struct Stdin(Mutex<State>);
 

src/io/stdout.rs

@@ -12,6 +12,12 @@ use crate::task::{blocking, Context, JoinHandle, Poll};
 ///
 /// [`std::io::stdout`]: https://doc.rust-lang.org/std/io/fn.stdout.html
 ///
+/// ### Note: Windows Portability Consideration
+///
+/// When operating in a console, the Windows implementation of this stream does not support
+/// non-UTF-8 byte sequences. Attempting to write bytes that are not valid UTF-8 will return
+/// an error.
+///
 /// # Examples
 ///
 /// ```no_run
@@ -35,12 +41,16 @@ pub fn stdout() -> Stdout {
 
 /// A handle to the standard output of the current process.
 ///
-/// Created by the [`stdout`] function.
+/// This writer is created by the [`stdout`] function. See its documentation
+/// for more.
+///
+/// ### Note: Windows Portability Consideration
 ///
-/// This type is an async version of [`std::io::Stdout`].
+/// When operating in a console, the Windows implementation of this stream does not support
+/// non-UTF-8 byte sequences. Attempting to write bytes that are not valid UTF-8 will return
+/// an error.
 ///
 /// [`stdout`]: fn.stdout.html
-/// [`std::io::Stdout`]: https://doc.rust-lang.org/std/io/struct.Stdout.html
 #[derive(Debug)]
 pub struct Stdout(Mutex<State>);
 

src/lib.rs

@@ -43,10 +43,11 @@
 
 #![cfg_attr(feature = "docs", feature(doc_cfg))]
 #![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)]
+#![allow(clippy::mutex_atomic, clippy::module_inception)]
 #![doc(test(attr(deny(rust_2018_idioms, warnings))))]
 #![doc(test(attr(allow(unused_extern_crates, unused_variables))))]
 #![doc(html_logo_url = "https://async.rs/images/logo--hero.svg")]
-#![recursion_limit = "1024"]
+#![recursion_limit = "2048"]
 
 #[macro_use]
 mod utils;

src/option/mod.rs

@@ -7,3 +7,8 @@ mod from_stream;
 
 #[doc(inline)]
 pub use std::option::Option;
+
+cfg_unstable! {
+    mod product;
+    mod sum;
+}

src/option/product.rs

@@ -0,0 +1,66 @@
+use std::pin::Pin;
+
+use crate::prelude::*;
+use crate::stream::{Stream, Product};
+
+impl<T, U> Product<Option<U>> for Option<T>
+where
+    T: Product<U>,
+{
+    #[doc = r#"
+        Takes each element in the `Stream`: if it is a `None`, no further
+        elements are taken, and the `None` is returned. Should no `None` occur,
+        the product of all elements is returned.
+
+        # Examples
+
+        This multiplies every integer in a vector, rejecting the product if a negative element is
+        encountered:
+
+        ```
+        # fn main() { async_std::task::block_on(async {
+        #
+        use std::collections::VecDeque;
+        use async_std::prelude::*;
+
+        let v: VecDeque<_> = vec![1, 2, 4].into_iter().collect();
+        let prod: Option<i32> = v.map(|x|
+            if x < 0 {
+                None
+            } else {
+                Some(x)
+            }).product().await;
+        assert_eq!(prod, Some(8));
+        #
+        # }) }
+        ```
+    "#]
+    fn product<'a, S>(stream: S) -> Pin<Box<dyn Future<Output = Option<T>> + 'a>>
+        where S: Stream<Item = Option<U>> + 'a
+    {
+        Box::pin(async move {
+            pin_utils::pin_mut!(stream);
+
+            // Using `scan` here because it is able to stop the stream early
+            // if a failure occurs
+            let mut found_none = false;
+            let out = <T as Product<U>>::product(stream
+                .scan((), |_, elem| {
+                    match elem {
+                        Some(elem) => Some(elem),
+                        None => {
+                            found_none = true;
+                            // Stop processing the stream on error
+                            None
+                        }
+                    }
+                })).await;
+
+            if found_none {
+                None
+            } else {
+                Some(out)
+            }
+        })
+    }
+}

src/option/sum.rs

@@ -0,0 +1,63 @@
+use std::pin::Pin;
+
+use crate::prelude::*;
+use crate::stream::{Stream, Sum};
+
+impl<T, U> Sum<Option<U>> for Option<T>
+where
+    T: Sum<U>,
+{
+    #[doc = r#"
+        Takes each element in the `Iterator`: if it is a `None`, no further
+        elements are taken, and the `None` is returned. Should no `None` occur,
+        the sum of all elements is returned.
+
+        # Examples
+
+        This sums up the position of the character 'a' in a vector of strings,
+        if a word did not have the character 'a' the operation returns `None`:
+
+        ```
+        # fn main() { async_std::task::block_on(async {
+        #
+        use std::collections::VecDeque;
+        use async_std::prelude::*;
+
+        let words: VecDeque<_> = vec!["have", "a", "great", "day"]
+            .into_iter()
+            .collect();
+        let total: Option<usize> = words.map(|w| w.find('a')).sum().await;
+        assert_eq!(total, Some(5));
+        #
+        # }) }
+        ```
+    "#]
+    fn sum<'a, S>(stream: S) -> Pin<Box<dyn Future<Output = Option<T>> + 'a>>
+        where S: Stream<Item = Option<U>> + 'a
+    {
+        Box::pin(async move {
+            pin_utils::pin_mut!(stream);
+
+            // Using `scan` here because it is able to stop the stream early
+            // if a failure occurs
+            let mut found_none = false;
+            let out = <T as Sum<U>>::sum(stream
+                .scan((), |_, elem| {
+                    match elem {
+                        Some(elem) => Some(elem),
+                        None => {
+                            found_none = true;
+                            // Stop processing the stream on error
+                            None
+                        }
+                    }
+                })).await;
+
+            if found_none {
+                None
+            } else {
+                Some(out)
+            }
+        })
+    }
+}

src/path/pathbuf.rs

@@ -1,6 +1,12 @@
 use std::ffi::{OsStr, OsString};
+#[cfg(feature = "unstable")]
+use std::pin::Pin;
 
 use crate::path::Path;
+#[cfg(feature = "unstable")]
+use crate::prelude::*;
+#[cfg(feature = "unstable")]
+use crate::stream::{Extend, FromStream, IntoStream};
 
 /// This struct is an async version of [`std::path::PathBuf`].
 ///
@@ -233,3 +239,44 @@ impl AsRef<std::path::Path> for PathBuf {
         self.inner.as_ref()
     }
 }
+
+#[cfg(feature = "unstable")]
+impl<P: AsRef<Path>> Extend<P> for PathBuf {
+    fn stream_extend<'a, S: IntoStream<Item = P>>(
+        &'a mut self,
+        stream: S,
+    ) -> Pin<Box<dyn Future<Output = ()> + 'a>>
+    where
+        P: 'a,
+        <S as IntoStream>::IntoStream: 'a,
+    {
+        let stream = stream.into_stream();
+
+        //TODO: This can be added back in once this issue is resolved:
+        // https://github.com/rust-lang/rust/issues/58234
+        //self.reserve(stream.size_hint().0);
+
+        Box::pin(stream.for_each(move |item| self.push(item.as_ref())))
+    }
+}
+
+#[cfg(feature = "unstable")]
+impl<'b, P: AsRef<Path> + 'b> FromStream<P> for PathBuf {
+    #[inline]
+    fn from_stream<'a, S: IntoStream<Item = P>>(
+        stream: S,
+    ) -> Pin<Box<dyn core::future::Future<Output = Self> + 'a>>
+    where
+        <S as IntoStream>::IntoStream: 'a,
+    {
+        let stream = stream.into_stream();
+
+        Box::pin(async move {
+            pin_utils::pin_mut!(stream);
+
+            let mut out = Self::new();
+            out.stream_extend(stream).await;
+            out
+        })
+    }
+}

src/result/mod.rs

@@ -7,3 +7,8 @@ mod from_stream;
 
 #[doc(inline)]
 pub use std::result::Result;
+
+cfg_unstable! {
+    mod product;
+    mod sum;
+}

src/result/product.rs

@@ -0,0 +1,64 @@
+use std::pin::Pin;
+
+use crate::prelude::*;
+use crate::stream::{Stream, Product};
+
+impl<T, U, E> Product<Result<U, E>> for Result<T, E>
+where
+    T: Product<U>,
+{
+    #[doc = r#"
+        Takes each element in the `Stream`: if it is an `Err`, no further
+        elements are taken, and the `Err` is returned. Should no `Err` occur,
+        the product of all elements is returned.
+
+        # Examples
+
+        This multiplies every integer in a vector, rejecting the product if a negative element is
+        encountered:
+
+        ```
+        # fn main() { async_std::task::block_on(async {
+        #
+        use std::collections::VecDeque;
+        use async_std::prelude::*;
+
+        let v: VecDeque<_> = vec![1, 2, 4].into_iter().collect();
+        let res: Result<i32, &'static str> = v.map(|x|
+            if x < 0 {
+                Err("Negative element found")
+            } else {
+                Ok(x)
+            }).product().await;
+        assert_eq!(res, Ok(8));
+        #
+        # }) }
+        ```
+    "#]
+    fn product<'a, S>(stream: S) -> Pin<Box<dyn Future<Output = Result<T, E>> + 'a>>
+        where S: Stream<Item = Result<U, E>> + 'a
+    {
+        Box::pin(async move {
+            pin_utils::pin_mut!(stream);
+
+            // Using `scan` here because it is able to stop the stream early
+            // if a failure occurs
+            let mut found_error = None;
+            let out = <T as Product<U>>::product(stream
+                .scan((), |_, elem| {
+                    match elem {
+                        Ok(elem) => Some(elem),
+                        Err(err) => {
+                            found_error = Some(err);
+                            // Stop processing the stream on error
+                            None
+                        }
+                    }
+                })).await;
+            match found_error {
+                Some(err) => Err(err),
+                None => Ok(out)
+            }
+        })
+    }
+}

src/result/sum.rs

@@ -0,0 +1,64 @@
+use std::pin::Pin;
+
+use crate::prelude::*;
+use crate::stream::{Stream, Sum};
+
+impl<T, U, E> Sum<Result<U, E>> for Result<T, E>
+where
+    T: Sum<U>,
+{
+    #[doc = r#"
+        Takes each element in the `Stream`: if it is an `Err`, no further
+        elements are taken, and the `Err` is returned. Should no `Err` occur,
+        the sum of all elements is returned.
+
+        # Examples
+
+        This sums up every integer in a vector, rejecting the sum if a negative
+        element is encountered:
+
+        ```
+        # fn main() { async_std::task::block_on(async {
+        #
+        use std::collections::VecDeque;
+        use async_std::prelude::*;
+
+        let v: VecDeque<_> = vec![1, 2].into_iter().collect();
+        let res: Result<i32, &'static str> = v.map(|x|
+            if x < 0 {
+                Err("Negative element found")
+            } else {
+                Ok(x)
+            }).sum().await;
+        assert_eq!(res, Ok(3));
+        #
+        # }) }
+        ```
+    "#]
+    fn sum<'a, S>(stream: S) -> Pin<Box<dyn Future<Output = Result<T, E>> + 'a>>
+        where S: Stream<Item = Result<U, E>> + 'a
+    {
+        Box::pin(async move {
+            pin_utils::pin_mut!(stream);
+
+            // Using `scan` here because it is able to stop the stream early
+            // if a failure occurs
+            let mut found_error = None;
+            let out = <T as Sum<U>>::sum(stream
+                .scan((), |_, elem| {
+                    match elem {
+                        Ok(elem) => Some(elem),
+                        Err(err) => {
+                            found_error = Some(err);
+                            // Stop processing the stream on error
+                            None
+                        }
+                    }
+                })).await;
+            match found_error {
+                Some(err) => Err(err),
+                None => Ok(out)
+            }
+        })
+    }
+}

src/stream/empty.rs

@@ -6,6 +6,11 @@ use crate::task::{Context, Poll};
 
 /// Creates a stream that doesn't yield any items.
 ///
+/// This `struct` is created by the [`empty`] function. See its
+/// documentation for more.
+///
+/// [`empty`]: fn.empty.html
+///
 /// # Examples
 ///
 /// ```

src/stream/exact_size_stream.rs

@@ -75,6 +75,7 @@ pub use crate::stream::Stream;
 /// assert_eq!(5, counter.len());
 /// # });
 /// ```
+#[allow(clippy::len_without_is_empty)] // ExactSizeIterator::is_empty is unstable
 #[cfg(feature = "unstable")]
 #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
 pub trait ExactSizeStream: Stream {

src/stream/from_fn.rs

@@ -10,7 +10,8 @@ use crate::task::{Context, Poll};
 pin_project! {
     /// A stream that yields elements by calling a closure.
     ///
-    /// This stream is constructed by [`from_fn`] function.
+    /// This stream is created by the [`from_fn`] function. See its
+    /// documentation for more.
     ///
     /// [`from_fn`]: fn.from_fn.html
     #[derive(Debug)]

src/stream/interval.rs

@@ -52,6 +52,10 @@ pub fn interval(dur: Duration) -> Interval {
 
 /// A stream representing notifications at fixed interval
 ///
+/// This stream is created by the [`interval`] function. See its
+/// documentation for more.
+///
+/// [`interval`]: fn.interval.html
 #[cfg(feature = "unstable")]
 #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
 #[derive(Debug)]
@@ -111,6 +115,7 @@ fn next_interval(prev: Instant, now: Instant, interval: Duration) -> Instant {
 #[cfg(test)]
 mod test {
     use super::next_interval;
+    use std::cmp::Ordering;
     use std::time::{Duration, Instant};
 
     struct Timeline(Instant);
@@ -134,12 +139,10 @@ mod test {
     // The math around Instant/Duration isn't 100% precise due to rounding
     // errors, see #249 for more info
     fn almost_eq(a: Instant, b: Instant) -> bool {
-        if a == b {
+        match a.cmp(&b) {
-            true
+            Ordering::Equal => true,
-        } else if a > b {
+            Ordering::Greater => a - b < Duration::from_millis(1),
-            a - b < Duration::from_millis(1)
+            Ordering::Less => b - a < Duration::from_millis(1),
-        } else {
-            b - a < Duration::from_millis(1)
         }
     }
 

src/stream/once.rs

@@ -29,7 +29,8 @@ pub fn once<T>(t: T) -> Once<T> {
 pin_project! {
     /// A stream that yields a single item.
     ///
-    /// This stream is constructed by the [`once`] function.
+    /// This stream is created by the [`once`] function. See its
+    /// documentation for more.
     ///
     /// [`once`]: fn.once.html
     #[derive(Debug)]

src/stream/product.rs

@@ -1,7 +1,9 @@
+use std::pin::Pin;
+
 use crate::future::Future;
 use crate::stream::Stream;
 
-/// Trait to represent types that can be created by productming up a stream.
+/// Trait to represent types that can be created by multiplying the elements of a stream.
 ///
 /// This trait is used to implement the [`product`] method on streams. Types which
 /// implement the trait can be generated by the [`product`] method. Like
@@ -16,8 +18,62 @@ use crate::stream::Stream;
 pub trait Product<A = Self>: Sized {
     /// Method which takes a stream and generates `Self` from the elements by
     /// multiplying the items.
-    fn product<S, F>(stream: S) -> F
+    fn product<'a, S>(stream: S) -> Pin<Box<dyn Future<Output = Self> + 'a>>
     where
-        S: Stream<Item = A>,
+        S: Stream<Item = A> + 'a;
-        F: Future<Output = Self>;
+}
+
+use core::ops::Mul;
+use core::num::Wrapping;
+use crate::stream::stream::StreamExt;
+
+macro_rules! integer_product {
+    (@impls $one: expr, $($a:ty)*) => ($(
+        impl Product for $a {
+            fn product<'a, S>(stream: S) -> Pin<Box<dyn Future<Output = Self>+ 'a>>
+            where
+                S: Stream<Item = $a> + 'a,
+            {
+                Box::pin(async move { stream.fold($one, Mul::mul).await } )
+            }
+        }
+        impl<'a> Product<&'a $a> for $a {
+            fn product<'b, S>(stream: S) -> Pin<Box<dyn Future<Output = Self> + 'b>>
+            where
+                S: Stream<Item = &'a $a> + 'b,
+            {
+                Box::pin(async move { stream.fold($one, Mul::mul).await } )
+            }
+        }
+    )*);
+    ($($a:ty)*) => (
+        integer_product!(@impls 1, $($a)*);
+        integer_product!(@impls Wrapping(1), $(Wrapping<$a>)*);
+    );
 }
+
+macro_rules! float_product {
+    ($($a:ty)*) => ($(
+        impl Product for $a {
+            fn product<'a, S>(stream: S) -> Pin<Box<dyn Future<Output = Self>+ 'a>>
+                where S: Stream<Item = $a> + 'a,
+            {
+                Box::pin(async move { stream.fold(1.0, |a, b| a * b).await } )
+            }
+        }
+        impl<'a> Product<&'a $a> for $a {
+            fn product<'b, S>(stream: S) -> Pin<Box<dyn Future<Output = Self>+ 'b>>
+                where S: Stream<Item = &'a $a> + 'b,
+            {
+                Box::pin(async move { stream.fold(1.0, |a, b| a * b).await } )
+            }
+        }
+    )*);
+    ($($a:ty)*) => (
+        float_product!($($a)*);
+        float_product!($(Wrapping<$a>)*);
+    );
+}
+
+integer_product!{ i8 i16 i32 i64 i128 isize u8 u16 u32 u64 u128 usize }
+float_product!{ f32 f64 }

src/stream/repeat.rs

@@ -29,7 +29,8 @@ where
 
 /// A stream that yields the same item repeatedly.
 ///
-/// This stream is constructed by the [`repeat`] function.
+/// This stream is created by the [`repeat`] function. See its
+/// documentation for more.
 ///
 /// [`repeat`]: fn.repeat.html
 #[derive(Debug)]

src/stream/repeat_with.rs

@@ -10,7 +10,8 @@ use crate::task::{Context, Poll};
 pin_project! {
     /// A stream that repeats elements of type `T` endlessly by applying a provided closure.
     ///
-    /// This stream is constructed by the [`repeat_with`] function.
+    /// This stream is created by the [`repeat_with`] function. See its
+    /// documentation for more.
     ///
     /// [`repeat_with`]: fn.repeat_with.html
     #[derive(Debug)]

src/stream/stream/chain.rs

@@ -8,6 +8,12 @@ use crate::task::{Context, Poll};
 
 pin_project! {
     /// Chains two streams one after another.
+    ///
+    /// This `struct` is created by the [`chain`] method on [`Stream`]. See its
+    /// documentation for more.
+    ///
+    /// [`chain`]: trait.Stream.html#method.chain
+    /// [`Stream`]: trait.Stream.html
     #[derive(Debug)]
     pub struct Chain<S, U> {
         #[pin]

src/stream/stream/filter.rs

@@ -8,6 +8,12 @@ use crate::task::{Context, Poll};
 
 pin_project! {
     /// A stream to filter elements of another stream with a predicate.
+    ///
+    /// This `struct` is created by the [`filter`] method on [`Stream`]. See its
+    /// documentation for more.
+    ///
+    /// [`filter`]: trait.Stream.html#method.filter
+    /// [`Stream`]: trait.Stream.html
     #[derive(Debug)]
     pub struct Filter<S, P, T> {
         #[pin]

src/stream/stream/flat_map.rs

@@ -0,0 +1,62 @@
+use pin_project_lite::pin_project;
+use std::pin::Pin;
+
+use crate::prelude::*;
+use crate::stream::stream::map::Map;
+use crate::stream::{IntoStream, Stream};
+use crate::task::{Context, Poll};
+
+pin_project! {
+    /// This `struct` is created by the [`flat_map`] method on [`Stream`]. See its
+    /// documentation for more.
+    ///
+    /// [`flat_map`]: trait.Stream.html#method.flat_map
+    /// [`Stream`]: trait.Stream.html
+    #[allow(missing_debug_implementations)]
+    pub struct FlatMap<S, U, T, F> {
+        #[pin]
+        stream: Map<S, F, T, U>,
+        #[pin]
+        inner_stream: Option<U>,
+    }
+}
+
+impl<S, U, F> FlatMap<S, U, S::Item, F>
+where
+    S: Stream,
+    U: IntoStream,
+    F: FnMut(S::Item) -> U,
+{
+    pub(super) fn new(stream: S, f: F) -> FlatMap<S, U, S::Item, F> {
+        FlatMap {
+            stream: stream.map(f),
+            inner_stream: None,
+        }
+    }
+}
+
+impl<S, U, F> Stream for FlatMap<S, U, S::Item, F>
+where
+    S: Stream,
+    S::Item: IntoStream<IntoStream = U, Item = U::Item>,
+    U: Stream,
+    F: FnMut(S::Item) -> U,
+{
+    type Item = U::Item;
+
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        let mut this = self.project();
+        loop {
+            if let Some(inner) = this.inner_stream.as_mut().as_pin_mut() {
+                if let item @ Some(_) = futures_core::ready!(inner.poll_next(cx)) {
+                    return Poll::Ready(item);
+                }
+            }
+
+            match futures_core::ready!(this.stream.as_mut().poll_next(cx)) {
+                None => return Poll::Ready(None),
+                Some(inner) => this.inner_stream.set(Some(inner.into_stream())),
+            }
+        }
+    }
+}

src/stream/stream/flatten.rs

@@ -0,0 +1,58 @@
+use pin_project_lite::pin_project;
+use std::pin::Pin;
+
+use crate::stream::{IntoStream, Stream};
+use crate::task::{Context, Poll};
+
+pin_project! {
+    /// This `struct` is created by the [`flatten`] method on [`Stream`]. See its
+    /// documentation for more.
+    ///
+    /// [`flatten`]: trait.Stream.html#method.flatten
+    /// [`Stream`]: trait.Stream.html
+    #[allow(missing_debug_implementations)]
+    pub struct Flatten<S, U> {
+        #[pin]
+        stream: S,
+        #[pin]
+        inner_stream: Option<U>,
+    }
+}
+
+impl<S> Flatten<S, S::Item>
+where
+    S: Stream,
+    S::Item: IntoStream,
+{
+    pub(super) fn new(stream: S) -> Flatten<S, S::Item> {
+        Flatten {
+            stream,
+            inner_stream: None,
+        }
+    }
+}
+
+impl<S, U> Stream for Flatten<S, <S::Item as IntoStream>::IntoStream>
+where
+    S: Stream,
+    S::Item: IntoStream<IntoStream = U, Item = U::Item>,
+    U: Stream,
+{
+    type Item = U::Item;
+
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        let mut this = self.project();
+        loop {
+            if let Some(inner) = this.inner_stream.as_mut().as_pin_mut() {
+                if let item @ Some(_) = futures_core::ready!(inner.poll_next(cx)) {
+                    return Poll::Ready(item);
+                }
+            }
+
+            match futures_core::ready!(this.stream.as_mut().poll_next(cx)) {
+                None => return Poll::Ready(None),
+                Some(inner) => this.inner_stream.set(Some(inner.into_stream())),
+            }
+        }
+    }
+}

src/stream/stream/fuse.rs

@@ -8,6 +8,12 @@ use crate::task::{Context, Poll};
 pin_project! {
     /// A `Stream` that is permanently closed once a single call to `poll` results in
     /// `Poll::Ready(None)`, returning `Poll::Ready(None)` for all future calls to `poll`.
+    ///
+    /// This `struct` is created by the [`fuse`] method on [`Stream`]. See its
+    /// documentation for more.
+    ///
+    /// [`fuse`]: trait.Stream.html#method.fuse
+    /// [`Stream`]: trait.Stream.html
     #[derive(Clone, Debug)]
     pub struct Fuse<S> {
         #[pin]

src/stream/stream/inspect.rs

@@ -8,6 +8,12 @@ use crate::task::{Context, Poll};
 
 pin_project! {
     /// A stream that does something with each element of another stream.
+    ///
+    /// This `struct` is created by the [`inspect`] method on [`Stream`]. See its
+    /// documentation for more.
+    ///
+    /// [`inspect`]: trait.Stream.html#method.inspect
+    /// [`Stream`]: trait.Stream.html
     #[derive(Debug)]
     pub struct Inspect<S, F, T> {
         #[pin]

src/stream/stream/merge.rs

@@ -7,9 +7,11 @@ use pin_project_lite::pin_project;
 pin_project! {
     /// A stream that merges two other streams into a single stream.
     ///
-    /// This stream is returned by [`Stream::merge`].
+    /// This `struct` is created by the [`merge`] method on [`Stream`]. See its
+    /// documentation for more.
     ///
-    /// [`Stream::merge`]: trait.Stream.html#method.merge
+    /// [`merge`]: trait.Stream.html#method.merge
+    /// [`Stream`]: trait.Stream.html
     #[cfg(feature = "unstable")]
     #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
     #[derive(Debug)]

src/stream/stream/mod.rs

@@ -93,13 +93,21 @@ use std::marker::PhantomData;
 
 cfg_unstable! {
     use std::pin::Pin;
+    use std::time::Duration;
 
     use crate::future::Future;
-    use crate::stream::FromStream;
+    use crate::stream::into_stream::IntoStream;
+    use crate::stream::{FromStream, Product, Sum};
 
     pub use merge::Merge;
+    pub use flatten::Flatten;
+    pub use flat_map::FlatMap;
+    pub use timeout::{TimeoutError, Timeout};
 
     mod merge;
+    mod flatten;
+    mod flat_map;
+    mod timeout;
 }
 
 extension_trait! {
@@ -559,6 +567,76 @@ extension_trait! {
             Filter::new(self, predicate)
         }
 
+        #[doc= r#"
+            Creates an stream that works like map, but flattens nested structure.
+
+            # Examples
+
+            Basic usage:
+
+            ```
+            # async_std::task::block_on(async {
+
+            use std::collections::VecDeque;
+            use async_std::prelude::*;
+            use async_std::stream::IntoStream;
+
+            let inner1: VecDeque<u8> = vec![1,2,3].into_iter().collect();
+            let inner2: VecDeque<u8> = vec![4,5,6].into_iter().collect();
+
+            let s: VecDeque<_> = vec![inner1, inner2].into_iter().collect();
+
+            let v :Vec<_> = s.flat_map(|s| s.into_stream()).collect().await;
+
+            assert_eq!(v, vec![1,2,3,4,5,6]);
+
+            # });
+            ```
+        "#]
+        #[cfg(feature = "unstable")]
+        #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
+        fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, Self::Item, F>
+            where
+                Self: Sized,
+                U: IntoStream,
+                F: FnMut(Self::Item) -> U,
+        {
+            FlatMap::new(self, f)
+        }
+
+        #[doc = r#"
+            Creates an stream that flattens nested structure.
+
+            # Examples
+
+            Basic usage:
+
+            ```
+            # async_std::task::block_on(async {
+
+            use std::collections::VecDeque;
+            use async_std::prelude::*;
+
+            let inner1: VecDeque<u8> = vec![1,2,3].into_iter().collect();
+            let inner2: VecDeque<u8> = vec![4,5,6].into_iter().collect();
+            let s: VecDeque<_> = vec![inner1, inner2].into_iter().collect();
+
+            let v: Vec<_> = s.flatten().collect().await;
+
+            assert_eq!(v, vec![1,2,3,4,5,6]);
+
+            # });
+        "#]
+        #[cfg(feature = "unstable")]
+        #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
+        fn flatten(self) -> Flatten<Self, Self::Item>
+        where
+            Self: Sized,
+            Self::Item: IntoStream,
+        {
+            Flatten::new(self)
+        }
+
         #[doc = r#"
             Both filters and maps a stream.
 
@@ -1084,6 +1162,40 @@ extension_trait! {
             Skip::new(self, n)
         }
 
+        #[doc=r#"
+            Await a stream or times out after a duration of time.
+
+            If you want to await an I/O future consider using
+            [`io::timeout`](../io/fn.timeout.html) instead.
+
+            # Examples
+
+            ```
+            # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
+            #
+            use std::time::Duration;
+
+            use async_std::stream;
+            use async_std::prelude::*;
+
+            let mut s = stream::repeat(1).take(3).timeout(Duration::from_secs(1));
+
+            while let Some(v) = s.next().await {
+                assert_eq!(v, Ok(1));
+            }
+            #
+            # Ok(()) }) }
+            ```
+        "#]
+        #[cfg(any(feature = "unstable", feature = "docs"))]
+        #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
+        fn timeout(self, dur: Duration) -> Timeout<Self>
+        where
+            Self: Stream + Sized,
+        {
+            Timeout::new(self, dur)
+        }
+
         #[doc = r#"
             A combinator that applies a function as long as it returns successfully, producing a single, final value.
             Immediately returns the error when the function returns unsuccessfully.
@@ -1536,6 +1648,95 @@ extension_trait! {
         {
             LtFuture::new(self, other)
         }
+
+        #[doc = r#"
+            Sums the elements of an iterator.
+
+            Takes each element, adds them together, and returns the result.
+
+            An empty iterator returns the zero value of the type.
+
+            # Panics
+
+            When calling `sum()` and a primitive integer type is being returned, this
+            method will panic if the computation overflows and debug assertions are
+            enabled.
+
+            # Examples
+
+            Basic usage:
+
+            ```
+            # fn main() { async_std::task::block_on(async {
+            #
+            use std::collections::VecDeque;
+            use async_std::prelude::*;
+
+            let s: VecDeque<_> = vec![0u8, 1, 2, 3, 4].into_iter().collect();
+            let sum: u8 = s.sum().await;
+
+            assert_eq!(sum, 10);
+            #
+            # }) }
+            ```
+        "#]
+        #[cfg(feature = "unstable")]
+        #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
+        fn sum<'a, S>(
+            self,
+        ) -> impl Future<Output = S> + 'a [Pin<Box<dyn Future<Output = S> + 'a>>]
+        where
+            Self: Sized + Stream<Item = S> + 'a,
+            S: Sum,
+        {
+            Sum::sum(self)
+        }
+
+        #[doc = r#"
+            Iterates over the entire iterator, multiplying all the elements
+
+            An empty iterator returns the one value of the type.
+
+            # Panics
+
+            When calling `product()` and a primitive integer type is being returned,
+            method will panic if the computation overflows and debug assertions are
+            enabled.
+
+            # Examples
+
+            This example calculates the factorial of n (i.e. the product of the numbers from 1 to
+            n, inclusive):
+
+            ```
+            # fn main() { async_std::task::block_on(async {
+            #
+            async fn factorial(n: u32) -> u32 {
+                use std::collections::VecDeque;
+                use async_std::prelude::*;
+
+                let s: VecDeque<_> = (1..=n).collect();
+                s.product().await
+            }
+
+            assert_eq!(factorial(0).await, 1);
+            assert_eq!(factorial(1).await, 1);
+            assert_eq!(factorial(5).await, 120);
+            #
+            # }) }
+            ```
+        "#]
+        #[cfg(feature = "unstable")]
+        #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
+        fn product<'a, P>(
+            self,
+        ) -> impl Future<Output = P> + 'a [Pin<Box<dyn Future<Output = P> + 'a>>]
+        where
+            Self: Sized + Stream<Item = P> + 'a,
+            P: Product,
+        {
+            Product::product(self)
+        }
     }
 
     impl<S: Stream + Unpin + ?Sized> Stream for Box<S> {

src/stream/stream/scan.rs

@@ -7,6 +7,12 @@ use crate::task::{Context, Poll};
 
 pin_project! {
     /// A stream to maintain state while polling another stream.
+    ///
+    /// This `struct` is created by the [`scan`] method on [`Stream`]. See its
+    /// documentation for more.
+    ///
+    /// [`scan`]: trait.Stream.html#method.scan
+    /// [`Stream`]: trait.Stream.html
     #[derive(Debug)]
     pub struct Scan<S, St, F> {
         #[pin]

src/stream/stream/skip.rs

@@ -7,6 +7,12 @@ use crate::stream::Stream;
 
 pin_project! {
     /// A stream to skip first n elements of another stream.
+    ///
+    /// This `struct` is created by the [`skip`] method on [`Stream`]. See its
+    /// documentation for more.
+    ///
+    /// [`skip`]: trait.Stream.html#method.skip
+    /// [`Stream`]: trait.Stream.html
     #[derive(Debug)]
     pub struct Skip<S> {
         #[pin]

src/stream/stream/skip_while.rs

@@ -8,6 +8,12 @@ use crate::task::{Context, Poll};
 
 pin_project! {
     /// A stream to skip elements of another stream based on a predicate.
+    ///
+    /// This `struct` is created by the [`skip_while`] method on [`Stream`]. See its
+    /// documentation for more.
+    ///
+    /// [`skip_while`]: trait.Stream.html#method.skip_while
+    /// [`Stream`]: trait.Stream.html
     #[derive(Debug)]
     pub struct SkipWhile<S, P, T> {
         #[pin]

src/stream/stream/step_by.rs

@@ -7,6 +7,12 @@ use crate::task::{Context, Poll};
 
 pin_project! {
     /// A stream that steps a given amount of elements of another stream.
+    ///
+    /// This `struct` is created by the [`step_by`] method on [`Stream`]. See its
+    /// documentation for more.
+    ///
+    /// [`step_by`]: trait.Stream.html#method.step_by
+    /// [`Stream`]: trait.Stream.html
     #[derive(Debug)]
     pub struct StepBy<S> {
         #[pin]

src/stream/stream/take.rs

@@ -7,6 +7,12 @@ use crate::task::{Context, Poll};
 
 pin_project! {
     /// A stream that yields the first `n` items of another stream.
+    ///
+    /// This `struct` is created by the [`take`] method on [`Stream`]. See its
+    /// documentation for more.
+    ///
+    /// [`take`]: trait.Stream.html#method.take
+    /// [`Stream`]: trait.Stream.html
     #[derive(Clone, Debug)]
     pub struct Take<S> {
         #[pin]

src/stream/stream/take_while.rs

@@ -8,6 +8,12 @@ use crate::task::{Context, Poll};
 
 pin_project! {
     /// A stream that yields elements based on a predicate.
+    ///
+    /// This `struct` is created by the [`take_while`] method on [`Stream`]. See its
+    /// documentation for more.
+    ///
+    /// [`take_while`]: trait.Stream.html#method.take_while
+    /// [`Stream`]: trait.Stream.html
     #[derive(Debug)]
     pub struct TakeWhile<S, P, T> {
         #[pin]

src/stream/stream/timeout.rs

@@ -0,0 +1,63 @@
+use std::error::Error;
+use std::fmt;
+use std::pin::Pin;
+use std::time::Duration;
+
+use futures_timer::Delay;
+use pin_project_lite::pin_project;
+
+use crate::future::Future;
+use crate::stream::Stream;
+use crate::task::{Context, Poll};
+
+pin_project! {
+    /// A stream with timeout time set
+    #[derive(Debug)]
+    pub struct Timeout<S: Stream> {
+        #[pin]
+        stream: S,
+        #[pin]
+        delay: Delay,
+    }
+}
+
+impl<S: Stream> Timeout<S> {
+    pub fn new(stream: S, dur: Duration) -> Timeout<S> {
+        let delay = Delay::new(dur);
+
+        Timeout { stream, delay }
+    }
+}
+
+impl<S: Stream> Stream for Timeout<S> {
+    type Item = Result<S::Item, TimeoutError>;
+
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        let this = self.project();
+
+        match this.stream.poll_next(cx) {
+            Poll::Ready(Some(v)) => Poll::Ready(Some(Ok(v))),
+            Poll::Ready(None) => Poll::Ready(None),
+            Poll::Pending => match this.delay.poll(cx) {
+                Poll::Ready(_) => Poll::Ready(Some(Err(TimeoutError { _private: () }))),
+                Poll::Pending => Poll::Pending,
+            },
+        }
+    }
+}
+
+/// An error returned when a stream times out.
+#[cfg_attr(feature = "docs", doc(cfg(unstable)))]
+#[cfg(any(feature = "unstable", feature = "docs"))]
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub struct TimeoutError {
+    _private: (),
+}
+
+impl Error for TimeoutError {}
+
+impl fmt::Display for TimeoutError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        "stream has timed out".fmt(f)
+    }
+}

src/stream/stream/zip.rs

@@ -8,6 +8,12 @@ use crate::task::{Context, Poll};
 
 pin_project! {
     /// An iterator that iterates two other iterators simultaneously.
+    ///
+    /// This `struct` is created by the [`zip`] method on [`Stream`]. See its
+    /// documentation for more.
+    ///
+    /// [`zip`]: trait.Stream.html#method.zip
+    /// [`Stream`]: trait.Stream.html
     pub struct Zip<A: Stream, B> {
         item_slot: Option<A::Item>,
         #[pin]

src/stream/sum.rs

@@ -1,3 +1,5 @@
+use std::pin::Pin;
+
 use crate::future::Future;
 use crate::stream::Stream;
 
@@ -16,8 +18,62 @@ use crate::stream::Stream;
 pub trait Sum<A = Self>: Sized {
     /// Method which takes a stream and generates `Self` from the elements by
     /// "summing up" the items.
-    fn sum<S, F>(stream: S) -> F
+    fn sum<'a, S>(stream: S) -> Pin<Box<dyn Future<Output = Self> + 'a>>
     where
-        S: Stream<Item = A>,
+        S: Stream<Item = A> + 'a;
-        F: Future<Output = Self>;
+}
+
+use core::ops::Add;
+use core::num::Wrapping;
+use crate::stream::stream::StreamExt;
+
+macro_rules! integer_sum {
+    (@impls $zero: expr, $($a:ty)*) => ($(
+        impl Sum for $a {
+            fn sum<'a, S>(stream: S) -> Pin<Box<dyn Future<Output = Self>+ 'a>>
+            where
+                S: Stream<Item = $a> + 'a,
+            {
+                Box::pin(async move { stream.fold($zero, Add::add).await } )
+            }
+        }
+        impl<'a> Sum<&'a $a> for $a {
+            fn sum<'b, S>(stream: S) -> Pin<Box<dyn Future<Output = Self> + 'b>>
+            where
+                S: Stream<Item = &'a $a> + 'b,
+            {
+                Box::pin(async move { stream.fold($zero, Add::add).await } )
+            }
+        }
+    )*);
+    ($($a:ty)*) => (
+        integer_sum!(@impls 0, $($a)*);
+        integer_sum!(@impls Wrapping(0), $(Wrapping<$a>)*);
+    );
 }
+
+macro_rules! float_sum {
+    ($($a:ty)*) => ($(
+        impl Sum for $a {
+            fn sum<'a, S>(stream: S) -> Pin<Box<dyn Future<Output = Self> + 'a>>
+                where S: Stream<Item = $a> + 'a,
+            {
+                Box::pin(async move { stream.fold(0.0, |a, b| a + b).await } )
+            }
+        }
+        impl<'a> Sum<&'a $a> for $a {
+            fn sum<'b, S>(stream: S) -> Pin<Box<dyn Future<Output = Self> + 'b>>
+                where S: Stream<Item = &'a $a> + 'b,
+            {
+                Box::pin(async move { stream.fold(0.0, |a, b| a + b).await } )
+            }
+        }
+    )*);
+    ($($a:ty)*) => (
+        float_sum!(@impls 0.0, $($a)*);
+        float_sum!(@impls Wrapping(0.0), $(Wrapping<$a>)*);
+    );
+}
+
+integer_sum!{ i8 i16 i32 i64 i128 isize u8 u16 u32 u64 u128 usize }
+float_sum!{ f32 f64 }

src/task/block_on.rs

@@ -154,6 +154,7 @@ where
 
 fn vtable() -> &'static RawWakerVTable {
     unsafe fn clone_raw(ptr: *const ()) -> RawWaker {
+        #![allow(clippy::redundant_clone)]
         let arc = ManuallyDrop::new(Arc::from_raw(ptr as *const Parker));
         mem::forget(arc.clone());
         RawWaker::new(ptr, vtable())

src/task/task.rs

@@ -167,6 +167,7 @@ impl Tag {
     }
 
     pub fn task(&self) -> &Task {
+        #[allow(clippy::transmute_ptr_to_ptr)]
         unsafe {
             let raw = self.raw_metadata.load(Ordering::Acquire);
 
@@ -189,6 +190,7 @@ impl Tag {
                 }
             }
 
+            #[allow(clippy::transmute_ptr_to_ptr)]
             mem::transmute::<&AtomicUsize, &Option<Task>>(&self.raw_metadata)
                 .as_ref()
                 .unwrap()

tests/buf_writer.rs

@@ -4,6 +4,7 @@ use async_std::task;
 
 #[test]
 fn test_buffered_writer() {
+    #![allow(clippy::cognitive_complexity)]
     task::block_on(async {
         let inner = Vec::new();
         let mut writer = BufWriter::with_capacity(2, inner);

tests/channel.rs

@@ -37,6 +37,7 @@ fn capacity() {
 
 #[test]
 fn len_empty_full() {
+    #![allow(clippy::cognitive_complexity)]
     task::block_on(async {
         let (s, r) = channel(2);
 

tests/rwlock.rs

@@ -13,7 +13,7 @@ use futures::channel::mpsc;
 /// Generates a random number in `0..n`.
 pub fn random(n: u32) -> u32 {
     thread_local! {
-        static RNG: Cell<Wrapping<u32>> = Cell::new(Wrapping(1406868647));
+        static RNG: Cell<Wrapping<u32>> = Cell::new(Wrapping(1_406_868_647));
     }
 
     RNG.with(|rng| {