|
| 1 | +--- |
| 2 | +layout: post |
| 3 | +title: "Announcing Rust 1.79.0" |
| 4 | +author: The Rust Release Team |
| 5 | +release: true |
| 6 | +--- |
| 7 | + |
| 8 | +The Rust team is happy to announce a new version of Rust, 1.79.0. Rust is a programming language empowering everyone to build reliable and efficient software. |
| 9 | + |
| 10 | +If you have a previous version of Rust installed via `rustup`, you can get 1.79.0 with: |
| 11 | + |
| 12 | +```console |
| 13 | +$ rustup update stable |
| 14 | +``` |
| 15 | + |
| 16 | +If you don't have it already, you can [get `rustup`](https://www.rust-lang.org/install.html) from the appropriate page on our website, and check out the [detailed release notes for 1.79.0](https://doc.rust-lang.org/nightly/releases.html#version-1790-2024-06-13). |
| 17 | + |
| 18 | +If you'd like to help us out by testing future releases, you might consider updating locally to use the beta channel (`rustup default beta`) or the nightly channel (`rustup default nightly`). Please [report](https://github.com/rust-lang/rust/issues/new/choose) any bugs you might come across! |
| 19 | + |
| 20 | +## What's in 1.79.0 stable |
| 21 | + |
| 22 | +### Inline `const` expressions |
| 23 | + |
| 24 | +`const { ... }` blocks are now stable in expression position, permitting |
| 25 | +explicitly entering a const context without requiring extra declarations (e.g., |
| 26 | +defining `const` items or associated constants on a trait). |
| 27 | + |
| 28 | +Unlike const items (`const ITEM: ... = ...`), inline consts are able to make |
| 29 | +use of in-scope generics, and have their type inferred rather than written explicitly, making them particularly useful for inline code snippets. For example, a pattern like: |
| 30 | + |
| 31 | +```rust |
| 32 | +const EMPTY: Option<Vec<u8>> = None; |
| 33 | +let foo = [EMPTY; 100]; |
| 34 | +``` |
| 35 | + |
| 36 | +can now be written like this: |
| 37 | + |
| 38 | +```rust |
| 39 | +let foo = [const { None }; 100]; |
| 40 | +``` |
| 41 | + |
| 42 | +Notably, this is also true of generic contexts, where previously a verbose trait declaration with an associated constant would be required: |
| 43 | + |
| 44 | +```rust |
| 45 | +fn create_none_array<T, const N: usize>() -> [Option<T>; N] { |
| 46 | + [const { None::<T> }; N] |
| 47 | +} |
| 48 | +``` |
| 49 | + |
| 50 | +This makes this code much more succinct and easier to read. |
| 51 | + |
| 52 | +See the [reference documentation](https://doc.rust-lang.org/nightly/reference/expressions/block-expr.html#const-blocks) for details. |
| 53 | + |
| 54 | +### Bounds in associated type position |
| 55 | + |
| 56 | +Rust 1.79 stabilizes the associated item bounds syntax, which allows us to put |
| 57 | +bounds in associated type position within other bounds, i.e. |
| 58 | +`T: Trait<Assoc: Bounds...>`. This avoids the need to provide an extra, |
| 59 | +explicit generic type just to constrain the associated type. |
| 60 | + |
| 61 | +This feature allows specifying bounds in a few places that previously either |
| 62 | +were not possible or imposed extra, unnecessary constraints on usage: |
| 63 | + |
| 64 | +* **`where` clauses** - in this position, this is equivalent to breaking up the bound into two (or more) `where` clauses. For example, `where T: Trait<Assoc: Bound>` is equivalent to `where T: Trait, <T as Trait>::Assoc: Bound`. |
| 65 | +* **Supertraits** - a bound specified via the new syntax is implied when the trait is used, unlike where clauses. Sample syntax: `trait CopyIterator: Iterator<Item: Copy> {}`. |
| 66 | +* **Associated type item bounds** - This allows constraining the *nested* rigid projections that are associated with a trait's associated types. e.g. `trait Trait { type Assoc: Trait2<Assoc2: Copy>; }`. |
| 67 | +* **opaque type bounds (RPIT, TAIT)** - This allows constraining associated types that are associated with the opaque type without having to *name* the opaque type. For example, `impl Iterator<Item: Copy>` defines an iterator whose item is `Copy` without having to actually name that item bound. |
| 68 | + |
| 69 | +See [the stabilization report](https://github.com/rust-lang/rust/pull/122055/#issue-2170532454) for more details. |
| 70 | + |
| 71 | +### Extending automatic temporary lifetime extension |
| 72 | + |
| 73 | +Temporaries which are immediately referenced in construction are now |
| 74 | +automatically lifetime extended in `match` and `if` constructs. This has the |
| 75 | +same behavior as lifetime extension for temporaries in block constructs. |
| 76 | + |
| 77 | +For example: |
| 78 | + |
| 79 | +```rust |
| 80 | +let a = if true { |
| 81 | + ..; |
| 82 | + &temp() // used to error, but now gets lifetime extended |
| 83 | +} else { |
| 84 | + ..; |
| 85 | + &temp() // used to error, but now gets lifetime extended |
| 86 | +}; |
| 87 | +``` |
| 88 | + |
| 89 | +and |
| 90 | + |
| 91 | +```rust |
| 92 | +let a = match () { |
| 93 | + _ => { |
| 94 | + ..; |
| 95 | + &temp() // used to error, but now gets lifetime extended |
| 96 | + } |
| 97 | +}; |
| 98 | +``` |
| 99 | + |
| 100 | +are now consistent with prior behavior: |
| 101 | + |
| 102 | +```rust |
| 103 | +let a = { |
| 104 | + ..; |
| 105 | + &temp() // lifetime is extended |
| 106 | +}; |
| 107 | +``` |
| 108 | + |
| 109 | +This behavior is backwards compatible since these programs used to fail compilation. |
| 110 | + |
| 111 | +### Frame pointers enabled in standard library builds |
| 112 | + |
| 113 | +The standard library distributed by the Rust project is now compiled with |
| 114 | +`-Cforce-frame-pointers=yes`, enabling downstream users to more easily profile |
| 115 | +their programs. Note that the standard library also continues to come up with |
| 116 | +line-level debug info (e.g., DWARF), though that is [stripped by default] in Cargo's release profiles. |
| 117 | + |
| 118 | +[stripped by default]: https://blog.rust-lang.org/2024/03/21/Rust-1.77.0.html#enable-strip-in-release-profiles-by-default |
| 119 | + |
| 120 | +### Stabilized APIs |
| 121 | + |
| 122 | +- [`{integer}::unchecked_add`](https://doc.rust-lang.org/stable/core/primitive.i32.html#method.unchecked_add) |
| 123 | +- [`{integer}::unchecked_mul`](https://doc.rust-lang.org/stable/core/primitive.i32.html#method.unchecked_mul) |
| 124 | +- [`{integer}::unchecked_sub`](https://doc.rust-lang.org/stable/core/primitive.i32.html#method.unchecked_sub) |
| 125 | +- [`<[T]>::split_at_unchecked`](https://doc.rust-lang.org/stable/core/primitive.slice.html#method.split_at_unchecked) |
| 126 | +- [`<[T]>::split_at_mut_unchecked`](https://doc.rust-lang.org/stable/core/primitive.slice.html#method.split_at_mut_unchecked) |
| 127 | +- [`<[u8]>::utf8_chunks`](https://doc.rust-lang.org/stable/core/primitive.slice.html#method.utf8_chunks) |
| 128 | +- [`str::Utf8Chunks`](https://doc.rust-lang.org/stable/core/str/struct.Utf8Chunks.html) |
| 129 | +- [`str::Utf8Chunk`](https://doc.rust-lang.org/stable/core/str/struct.Utf8Chunk.html) |
| 130 | +- [`<*const T>::is_aligned`](https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_aligned) |
| 131 | +- [`<*mut T>::is_aligned`](https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_aligned-1) |
| 132 | +- [`NonNull::is_aligned`](https://doc.rust-lang.org/stable/core/ptr/struct.NonNull.html#method.is_aligned) |
| 133 | +- [`<*const [T]>::len`](https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.len) |
| 134 | +- [`<*mut [T]>::len`](https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.len-1) |
| 135 | +- [`<*const [T]>::is_empty`](https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_empty) |
| 136 | +- [`<*mut [T]>::is_empty`](https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_empty-1) |
| 137 | +- [`NonNull::<[T]>::is_empty`](https://doc.rust-lang.org/stable/core/ptr/struct.NonNull.html#method.is_empty) |
| 138 | +- [`CStr::count_bytes`](https://doc.rust-lang.org/stable/core/ffi/c_str/struct.CStr.html#method.count_bytes) |
| 139 | +- [`io::Error::downcast`](https://doc.rust-lang.org/stable/std/io/struct.Error.html#method.downcast) |
| 140 | +- [`num::NonZero<T>`](https://doc.rust-lang.org/stable/core/num/struct.NonZero.html) |
| 141 | +- [`path::absolute`](https://doc.rust-lang.org/stable/std/path/fn.absolute.html) |
| 142 | +- [`proc_macro::Literal::byte_character`](https://doc.rust-lang.org/stable/proc_macro/struct.Literal.html#method.byte_character) |
| 143 | +- [`proc_macro::Literal::c_string`](https://doc.rust-lang.org/stable/proc_macro/struct.Literal.html#method.c_string) |
| 144 | + |
| 145 | +These APIs are now stable in const contexts: |
| 146 | + |
| 147 | +- [`Atomic*::into_inner`](https://doc.rust-lang.org/stable/core/sync/atomic/struct.AtomicUsize.html#method.into_inner) |
| 148 | +- [`io::Cursor::new`](https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.new) |
| 149 | +- [`io::Cursor::get_ref`](https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.get_ref) |
| 150 | +- [`io::Cursor::position`](https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.position) |
| 151 | +- [`io::empty`](https://doc.rust-lang.org/stable/std/io/fn.empty.html) |
| 152 | +- [`io::repeat`](https://doc.rust-lang.org/stable/std/io/fn.repeat.html) |
| 153 | +- [`io::sink`](https://doc.rust-lang.org/stable/std/io/fn.sink.html) |
| 154 | +- [`panic::Location::caller`](https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.caller) |
| 155 | +- [`panic::Location::file`](https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.file) |
| 156 | +- [`panic::Location::line`](https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.line) |
| 157 | +- [`panic::Location::column`](https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.column) |
| 158 | + |
| 159 | + |
| 160 | +### Other changes |
| 161 | + |
| 162 | +Check out everything that changed in [Rust](https://github.com/rust-lang/rust/releases/tag/1.79.0), [Cargo](https://github.com/rust-lang/cargo/blob/master/CHANGELOG.md#cargo-179-2024-06-13), and [Clippy](https://github.com/rust-lang/rust-clippy/blob/master/CHANGELOG.md#rust-179). |
| 163 | + |
| 164 | +## Contributors to 1.79.0 |
| 165 | + |
| 166 | +Many people came together to create Rust 1.79.0. We couldn't have done it without all of you. [Thanks!](https://thanks.rust-lang.org/rust/1.79.0/) |
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