Rust 1.23 release

_posts/2018-01-04-Rust-1.23.md

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+---
+layout: post
+title: "Announcing Rust 1.23"
+author: The Rust Core Team
+---
+
+The Rust team is happy to announce a new version of Rust, 1.23.0. Rust is a
+systems programming language focused on safety, speed, and concurrency.
+
+If you have a previous version of Rust installed via rustup, getting Rust
+1.23.0 is as easy as:
+
+```bash
+$ rustup update stable
+```
+
+If you don't have it already, you can [get `rustup`][install] from the
+appropriate page on our website, and check out the [detailed release notes for
+1.23.0][notes] on GitHub.
+
+[install]: https://www.rust-lang.org/install.html
+[notes]: https://github.com/rust-lang/rust/blob/master/RELEASES.md#version-1230-2018-01-04
+
+## What's in 1.23.0 stable
+
+New year, new Rust! For our first improvement today, we now [avoid some uneccesary
+copies](https://github.com/rust-lang/rust/pull/45380) in certain situations.
+We've seen memory usage drop 5-10% with this change.
+
+The documentation team has been on a long journey to move `rustdoc` to use
+[CommonMark]. Previously, `rustdoc` never guaranteed which markdown rendering
+engine it used, but we're finally committing to CommonMark. As part of this
+release, we render the documentation with our previous renderer, [Hoedown],
+but also render it with a CommonMark compliant renderer, and [warn if there
+are any differences]. There should be a way for you to modify the syntax you
+use to render correctly under both; we're not aware of any situations where
+this is impossible. Docs team member Guillaume Gomez has [written a blog post]
+showing some common differences and how to solve them. In a future release,
+we will switch to using the CommonMark renderer by default. This [warning
+landed in nightly in May of last year], and has been on by default [since
+October of last year], so many crates have already fixed any issues that
+they've found.
+
+[CommonMark]: http://commonmark.org/
+[Hoedown]: https://github.com/hoedown/hoedown
+[warn if there are any differences]: https://github.com/rust-lang/rust/pull/45324
+[written a blog post]: https://blog.guillaume-gomez.fr/articles/2017-09-18+New+rustdoc+rendering+common+errors
+[warning landed in nightly in May of last year]: https://github.com/rust-lang/rust/pull/41991
+[since October of last year]: https://github.com/rust-lang/rust/pull/45324
+
+In other documentation news, historically, Cargo's docs have been a bit strange.
+Rather than being on [https://doc.rust-lang.org][], they've been at [https://doc.crates.io][].
+With this release, [that's changing](https://github.com/rust-lang/rust/pull/45692).
+You can now find Cargo's docs at [https://doc.rust-lang.org/cargo][]. Additionally, they've
+been converted to the same format as our other long-form documentation. We'll be
+adding a redirect from `doc.crates.io` to this page, and you can expect to see more
+improvements and updates to Cargo's docs throughout the year.
+
+See the [detailed release notes][notes] for more.
+
+### Library stabilizations
+
+As of Rust 1.0, a trait named [`AsciiExt`] existed to provide ASCII related functionality
+on `u8`, `char`, `[u8]`, and `str`. To use it, you'd write code like this:
+
+```rust
+use std::ascii::AsciiExt;
+
+let ascii = 'a';
+let non_ascii = '❤';
+let int_ascii = 97;
+
+assert!(ascii.is_ascii());
+assert!(!non_ascii.is_ascii());
+assert!(int_ascii.is_ascii());
+```
+
+In Rust 1.23, these methods are now defined directly on those types, and so you no longer need
+to import the trait. Thanks to our stability guarantees, this trait still exists, so if you'd
+like to still support Rust versions before Rust 1.23, you can do this:
+
+```rust
+#[warn(unused_imports)]
+use std::ascii::AsciiExt;
+```
+
+To supress the related warning. Once you drop support for older Rusts, you
+can remove both lines, and everything will continue to work.
+
+[`AsciiExt`]: https://doc.rust-lang.org/std/ascii/trait.AsciiExt.html
+
+Additionally, a few new APIs were stabilized this release:
+
+* The various [`std::sync::atomic
+  types`](https://doc.rust-lang.org/beta/std/sync/atomic/index.html#structs)
+  now implement `From` their non-atomic types. For example, `let x = AtomicBool::from(true);`.
+* [`()` now implements `FromIterator<()>`](https://github.com/rust-lang/rust/pull/45379); check the PR for
+  a neat use-case.
+* [`RwLock<T>` has had its `Send` restriction lifted](https://github.com/rust-lang/rust/pull/45682)
+
+See the [detailed release notes][notes] for more.
+
+### Cargo features
+
+`cargo check` can now [check your unit tests](https://github.com/rust-lang/cargo/pull/4592).
+
+`cargo uninstall` can now [uninstall more than one package in one command](https://github.com/rust-lang/cargo/pull/4561).
+
+See the [detailed release notes][notes] for more.
+
+## Contributors to 1.23.0
+
+Many people came together to create Rust 1.23. We couldn't have done it
+without all of you. [Thanks!](https://thanks.rust-lang.org/rust/1.23.0)