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‎posts/2024-06-13-Rust-1.79.0.md

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---
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layout: post
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title: "Announcing Rust 1.79.0"
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author: The Rust Release Team
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release: true
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---
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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.
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If you have a previous version of Rust installed via `rustup`, you can get 1.79.0 with:
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```console
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$ rustup update stable
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```
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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).
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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!
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## What's in 1.79.0 stable
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### Inline `const` expressions
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`const { ... }` blocks are now stable in expression position, permitting
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explicitly entering a const context without requiring extra declarations (e.g.,
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defining `const` items or associated constants on a trait).
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Unlike const items (`const ITEM: ... = ...`), inline consts are able to make
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use of in-scope generics, making them particularly useful for inline code snippets. For example, a pattern like:
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```rust
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const EMPTY: Option<Vec<u8>> = None;
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let foo = [EMPTY; 100];
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```
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can now be written like this:
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```rust
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let foo = [const { None }; 100];
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```
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Notably, this is also true of generic contexts, where previously a verbose trait declaration with an associated constant would be required:
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```rust
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fn create_none_array<T, const N: usize>() -> [Option<T>; N] {
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[const { None::<T> }; N]
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}
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```
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This makes this code much more succinct and easier to read.
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See the [reference documentation](https://doc.rust-lang.org/nightly/reference/expressions/block-expr.html#const-blocks) for details.
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### Accept bounds in associated type position
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Rust 1.79 stabilizes the associated item bounds syntax, which allows us to put
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bounds in associated type position within other bounds, i.e.
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`T: Trait<Assoc: Bounds...>`. This avoids the need to provide an extra,
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explicit generic type just to constrain the associated type.
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This feature allows specifying bounds in a few places that previously either
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were not possible or imposed extra, unnecessary constraints on usage:
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* **`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`.
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* **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> {}`.
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* **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>; }`.
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* **opaque item bounds (RPIT, TAIT)** - This allows constraining associated types that are associated with the opaque without having to *name* the opaque. For example, `impl Iterator<Item: Copy>` defines an iterator whose item is `Copy` without having to actually name that item bound.
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See [stabilization report](https://github.com/rust-lang/rust/pull/122055/#issue-2170532454) for more details.
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### Extending automatic temporary lifetime extension
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Continuing the efforts of removing unnecessary lifetime-related errors,
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temporaries which are immediately referenced in construction are now
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automatically lifetime extended in `match` and `if` constructs. This has the
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same behavior as lifetime extension for temporaries in block constructs.
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For example:
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```rust
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let a = if true {
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..;
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&temp() // used to error, but now gets lifetime extended
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} else {
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..;
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&temp() // used to error, but now gets lifetime extended
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};
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```
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and
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```rust
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let a = match () {
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_ => {
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..;
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&temp() // used to error, but now gets lifetime extended
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}
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};
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```
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are now consistent with prior behavior:
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```rust
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let a = {
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..;
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&temp() // lifetime is extended
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};
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```
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This behavior is backwards compatible since these programs used to fail compilation.
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### Frame pointers enabled in standard library builds
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The standard library distributed by the Rust project is now compiled with
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`-Cforce-frame-pointers=yes`, enabling downstream users to more easily profile
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their programs. Note that the standard library also continues to come up with
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line-level debug info (e.g., DWARF), though that is [stripped by default] in Cargo's release profiles.
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[stripped by default]: https://blog.rust-lang.org/2024/03/21/Rust-1.77.0.html#enable-strip-in-release-profiles-by-default
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### Stabilized APIs
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- [`{integer}::unchecked_add`](https://doc.rust-lang.org/stable/core/primitive.i32.html#method.unchecked_add)
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- [`{integer}::unchecked_mul`](https://doc.rust-lang.org/stable/core/primitive.i32.html#method.unchecked_mul)
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- [`{integer}::unchecked_sub`](https://doc.rust-lang.org/stable/core/primitive.i32.html#method.unchecked_sub)
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- [`<[T]>::split_at_unchecked`](https://doc.rust-lang.org/stable/core/primitive.slice.html#method.split_at_unchecked)
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- [`<[T]>::split_at_mut_unchecked`](https://doc.rust-lang.org/stable/core/primitive.slice.html#method.split_at_mut_unchecked)
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- [`<[u8]>::utf8_chunks`](https://doc.rust-lang.org/stable/core/primitive.slice.html#method.utf8_chunks)
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- [`str::Utf8Chunks`](https://doc.rust-lang.org/stable/core/str/struct.Utf8Chunks.html)
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- [`str::Utf8Chunk`](https://doc.rust-lang.org/stable/core/str/struct.Utf8Chunk.html)
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- [`<*const T>::is_aligned`](https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_aligned)
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- [`<*mut T>::is_aligned`](https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_aligned-1)
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- [`NonNull::is_aligned`](https://doc.rust-lang.org/stable/core/ptr/struct.NonNull.html#method.is_aligned)
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- [`<*const [T]>::len`](https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.len)
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- [`<*mut [T]>::len`](https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.len-1)
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- [`<*const [T]>::is_empty`](https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_empty)
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- [`<*mut [T]>::is_empty`](https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_empty-1)
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- [`NonNull::<[T]>::is_empty`](https://doc.rust-lang.org/stable/core/ptr/struct.NonNull.html#method.is_empty)
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- [`CStr::count_bytes`](https://doc.rust-lang.org/stable/core/ffi/c_str/struct.CStr.html#method.count_bytes)
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- [`io::Error::downcast`](https://doc.rust-lang.org/stable/std/io/struct.Error.html#method.downcast)
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- [`num::NonZero<T>`](https://doc.rust-lang.org/stable/core/num/struct.NonZero.html)
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- [`path::absolute`](https://doc.rust-lang.org/stable/std/path/fn.absolute.html)
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- [`proc_macro::Literal::byte_character`](https://doc.rust-lang.org/stable/proc_macro/struct.Literal.html#method.byte_character)
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- [`proc_macro::Literal::c_string`](https://doc.rust-lang.org/stable/proc_macro/struct.Literal.html#method.c_string)
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These APIs are now stable in const contexts:
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- [`Atomic*::into_inner`](https://doc.rust-lang.org/stable/core/sync/atomic/struct.AtomicUsize.html#method.into_inner)
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- [`io::Cursor::new`](https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.new)
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- [`io::Cursor::get_ref`](https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.get_ref)
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- [`io::Cursor::position`](https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.position)
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- [`io::empty`](https://doc.rust-lang.org/stable/std/io/fn.empty.html)
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- [`io::repeat`](https://doc.rust-lang.org/stable/std/io/fn.repeat.html)
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- [`io::sink`](https://doc.rust-lang.org/stable/std/io/fn.sink.html)
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- [`panic::Location::caller`](https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.caller)
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- [`panic::Location::file`](https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.file)
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- [`panic::Location::line`](https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.line)
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- [`panic::Location::column`](https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.column)
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### Other changes
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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).
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## Contributors to 1.79.0
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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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