polish lib.rs examples

.github/workflows/ci.yml

@@ -62,7 +62,7 @@ jobs:
       uses: actions-rs/cargo@v1
       with:
         command: test
-        args: --all --features unstable
+        args: --all --features unstable attributes
 
   check_fmt_and_docs:
     name: Checking fmt and docs

README.md

@@ -74,20 +74,28 @@ syntax.
 
 ## Examples
 
+All examples require the [`"attributes"` feature] to be enabled.  This feature
+is not enabled by default because it significantly impacts compile times. See
+[`task::block_on`] for an alternative way to start executing tasks.
+
 ```rust
-use async_std::task;
+async fn say_hello() {
+    println!("Hello, world!");
+}
 
-fn main() {
-    task::block_on(async {
-        println!("Hello, world!");
-    })
+#[async_std::main]
+async fn main() {
+    say_hello().await;
 }
 ```
 
 More examples, including networking and file access, can be found in our
-[`examples`] directory.
+[`examples`] directory and in our [documentation].
 
 [`examples`]: https://github.com/async-rs/async-std/tree/master/examples
+[documentation]: https://docs.rs/async-std#examples
+[`task::block_on`]: task/fn.block_on.html
+[`"attributes"` feature]: https://docs.rs/async-std/#features
 
 ## Philosophy
 

src/lib.rs

@@ -131,17 +131,55 @@
 //!
 //! # Examples
 //!
-//! Spawn a task and block the current thread on its result:
+//! All examples require the [`"attributes"` feature](#features) to be enabled.
+//! This feature is not enabled by default because it significantly impacts
+//! compile times. See [`task::block_on`] for an alternative way to start
+//! executing tasks.
 //!
+//! Call an async function from the main function:
+//!
+//! ```
+//! async fn say_hello() {
+//!     println!("Hello, world!");
+//! }
+//!
+//! #[async_std::main]
+//! async fn main() {
+//!     say_hello().await;
+//! }
+//! ```
+//!
+//! Await two futures concurrently, and return a tuple of their output:
+//!
+//! ```
+//! #[async_std::main]
+//! async fn main() {
+//!     let a = async { 1u8 };
+//!     let b = async { 2u8 };
+//!     assert_eq!(a.join(b).await, (1u8, 2u8))
+//! }
 //! ```
-//! use async_std::task;
 //!
-//! fn main() {
-//!     task::block_on(async {
-//!         println!("Hello, world!");
-//!     })
+//! Create a UDP server that echoes back each received message to the sender:
+//!
+//! ```no_run
+//! use async_std::net::UdpSocket;
+//!
+//! #[async_std::main]
+//! async fn main() -> std::io::Result<()> {
+//!     let mut socket = UdpSocket::bind("127.0.0.1:8080")?;
+//!     println!("Listening on {}", socket.local_addr()?);
+//!
+//!     let mut buf = vec![0u8; 1024];
+//!
+//!     loop {
+//!         let (recv, peer) = socket.recv_from(&mut buf).await?;
+//!         let sent = socket.send_to(&buf[..recv], &peer).await?;
+//!         println!("Sent {} out of {} bytes to {}", sent, recv, peer);
+//!     }
 //! }
 //! ```
+//! [`task::block_on`]: task/fn.block_on.html
 //!
 //! # Features
 //!

src/task/block_on.rs

@@ -28,9 +28,11 @@ use crate::task::{Context, Poll, Task, Waker};
 /// ```no_run
 /// use async_std::task;
 ///
-/// task::block_on(async {
-///     println!("Hello, world!");
-/// })
+/// fn main() {
+///     task::block_on(async {
+///         println!("Hello, world!");
+///     })
+/// }
 /// ```
 pub fn block_on<F, T>(future: F) -> T
 where