Merge pull request #213 from rust-lang/1.22-announcement

1.22 announcement

Author: aturon

_posts/2017-11-22-Rust-1.22.md

@@ -0,0 +1,176 @@
+---
+layout: post
+title: "Announcing Rust 1.22 (and 1.22.1)"
+author: The Rust Core Team
+---
+
+The Rust team is happy to announce *two* new versions of Rust, 1.22.0 and
+1.22.1. Rust is a systems programming language focused on safety, speed, and
+concurrency.
+
+> Wait, two versions? At the last moment, we [discovered a a late-breaking
+> issue with the new macOS High
+> Sierra](https://github.com/rust-lang/rust/pull/46183) in 1.22.0, and for
+> various reasons, decided to release 1.22.0 as usual, but also put out a
+> 1.22.1 with the patch. The bug is actually in Cargo, not `rustc`, and only
+> affects users on macOS High Sierra.
+
+If you have a previous version of Rust installed via rustup, getting Rust
+1.22.1 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
+1.22.0][notes] and 1.22.1 on GitHub.
+
+[install]: https://www.rust-lang.org/install.html
+[notes]: https://github.com/rust-lang/rust/blob/master/RELEASES.md#version-1220-2017-11-22
+
+## What's in 1.22.0 and 1.22.1 stable
+
+The headline feature for this release is one many have been anticipating for
+a long time: you can now [use `?` with `Option<T>`]! About a year ago, in
+[Rust 1.13], we introduced the `?` operator for working with `Result<T, E>`.
+Ever since then, there's been discussion about how far `?` should go: should
+it stay only for results? Should it be user-extensible? Should it be
+usable with `Option<T>`?
+
+In Rust 1.22, basic usage of `?` with `Option<T>` is now stable.
+This code will now compile:
+
+```rust
+fn try_option_some() -> Option<u8> {
+    let val = Some(1)?;
+    Some(val)
+}
+assert_eq!(try_option_some(), Some(1));
+
+fn try_option_none() -> Option<u8> {
+    let val = None?;
+    Some(val)
+}
+assert_eq!(try_option_none(), None);
+```
+
+However, this functionality is still a bit limited; you cannot yet write
+code that mixes results and options with `?` in the same function, for
+example. This will be possible in the future, and already is in nightly
+Rust; expect to hear more about this in a future release.
+
+[use `?` with `Option<T>`]: https://github.com/rust-lang/rust/pull/42526
+[Rust 1.13]: https://blog.rust-lang.org/2016/11/10/Rust-1.13.html
+
+Types that implement `Drop` are [now allowed in `const` and `static`
+items](https://github.com/rust-lang/rust/pull/44456). Like this:
+
+```rust
+struct Foo {
+    a: u32
+}
+
+impl Drop for Foo {
+    fn drop(&mut self) {}
+}
+
+const F : Foo = Foo { a : 0 };
+static S : Foo = Foo { a : 0 };
+```
+
+This change doesn't bring much on its own, but as we improve our
+ability to compute things at compile-time, more and more will be
+possible in `const` and `static`.
+
+Additionally, some small quality-of-life improvements:
+
+[Two] recent [compiler changes] should speed up compiles in debug mode. We
+don't have any specific numbers to commit to with these changes, but as
+always, compile times are very important to us, and we're continuing to
+work on improving them.
+
+[Two]: https://github.com/rust-lang/rust/pull/45075
+[compiler changes]: https://github.com/rust-lang/rust/pull/45064
+
+[`T op= &T` now works for primitive types][add], which is a fancy way of saying:
+
+```rust
+let mut x = 2;
+let y = &8;
+
+// this didn't work, but now does
+x += y;
+```
+
+Previously, you'd have needed to write `x += *y` in order to de-reference, so
+this solves a small papercut.
+
+[add]: https://github.com/rust-lang/rust/pull/44287
+
+[Backtraces are improved on MacOS](https://github.com/rust-lang/rust/pull/44251).
+
+You can now [create `compile-fail` tests in Rustdoc], like this:
+
+```
+/// ```compile_fail
+/// let x = 5;
+/// x += 2; // shouldn't compile!
+/// ```
+```
+
+Please note that these kinds of tests can be more fragile than others, as
+additions to Rust may cause code to compile when it previously would not.
+Consider the first announcement with `?`, for example: that code would fail
+to compile on Rust 1.21, but compile successfully on Rust 1.22, causing your
+test suite to start failing.
+
+[create `compile-fail` tests in Rustdoc]: https://github.com/rust-lang/rust/pull/43949
+
+Finally, we [removed support for the `le32-unknown-nacl`
+target](https://github.com/rust-lang/rust/pull/45041). Google itself [has
+deprecated
+PNaCl](https://blog.chromium.org/2017/05/goodbye-pnacl-hello-webassembly.html),
+instead throwing its support behind [WebAssembly](http://webassembly.org/).
+You can already compile Rust code to WebAssembly today, and you can expect
+to hear more developments regarding this in future releases.
+
+See the [detailed release notes][notes] for more.
+
+### Library stabilizations
+
+A few new APIs were stabilized this release:
+
+- [`Box<Error>` now impls `From<Cow<str>>`][44466]
+- [`std::mem::Discriminant` is now guaranteed to be `Send + Sync`][45095]
+- [`fs::copy` now returns the length of the main stream on NTFS.][44895]
+- [Properly detect overflow in `Instant += Duration`.][44220]
+- [impl `Hasher` for `{&mut Hasher, Box<Hasher>}`][44015]
+- [impl `fmt::Debug` for `SplitWhitespace`.][44303]
+
+[44466]: https://github.com/rust-lang/rust/pull/44466
+[45095]: https://github.com/rust-lang/rust/pull/45095
+[44895]: https://github.com/rust-lang/rust/pull/44895
+[44220]: https://github.com/rust-lang/rust/pull/44220
+[44015]: https://github.com/rust-lang/rust/pull/44015
+[44303]: https://github.com/rust-lang/rust/pull/44303
+
+See the [detailed release notes][notes] for more.
+
+### Cargo features
+
+If you have a big example to show your users, Cargo has grown
+the ability to [build multi-file
+examples](https://github.com/rust-lang/cargo/pull/4496) by
+creating a subdirectory inside `examples` that contains a
+`main.rs`.
+
+Cargo now has the ability to [vendor git repositories](https://github.com/rust-lang/cargo/pull/3992).
+
+See the [detailed release notes][notes] for more.
+
+## Contributors to 1.22.0 and 1.22.1
+
+Many people came together to create Rust 1.22. We couldn't have done it
+without all of you. [Thanks!](https://thanks.rust-lang.org/rust/1.22.0) (and
+[Thanks again!](https://thanks.rust-lang.org/rust/1.22.1))