Announcing Rust 1.80.0

The Rust team just announced the release of Rust 1.80.0.

This article aims to give you a quick recap of the main updates.

To update to this latest version, run:

$ rustup update stable

Key Updates in Rust 1.80.0

LazyCell and LazyLock

These new types delay data initialization until first access.

LazyLock is thread-safe, suitable for static values, while LazyCell is not thread-safe but can be used in thread-local statics.

Example using LazyLock:

use std::sync::LazyLock;
use std::time::Instant;

static LAZY_TIME: LazyLock<Instant> = LazyLock::new(Instant::now);

fn main() {
    let start = Instant::now();
    std::thread::scope(|s| {
        s.spawn(|| {
            println!("Thread lazy time is {:?}", LAZY_TIME.duration_since(start));
        });
        println!("Main lazy time is {:?}", LAZY_TIME.duration_since(start));
    });
}

Checked cfg Names and Values

Cargo 1.80 now includes checks for cfg names and values to catch typos and misconfigurations, improving the reliability of conditional configurations.

Example demonstrating cfg check:

fn main() {
    println!("Hello, world!");

    #[cfg(feature = "crayon")]
    rayon::join(
        || println!("Hello, Thing One!"),
        || println!("Hello, Thing Two!"),
    );
}

Warning output:

warning: unexpected `cfg` condition value: `crayon`
 --> src/main.rs:4:11
  |
4 |     #[cfg(feature = "crayon")]
  |           ^^^^^^^^^^--------
  |                     |
  |                     help: there is an expected value with a similar name: `"rayon"`
  |
  = note: expected values for `feature` are: `rayon`
  = help: consider adding `crayon` as a feature in `Cargo.toml`

Exclusive Ranges in Patterns

Rust now supports exclusive range patterns (a..b), enhancing pattern matching and reducing the need for separate constants for inclusive endpoints.

Example using exclusive range patterns:

pub fn size_prefix(n: u32) -> &'static str {
    const K: u32 = 10u32.pow(3);
    const M: u32 = 10u32.pow(6);
    const G: u32 = 10u32.pow(9);
    match n {
        ..K => "",
        K..M => "k",
        M..G => "M",
        G.. => "G",
    }
}

Stabilized APIs

New stable APIs include implementations for Rc and Arc types, enhancements to Duration, Option, Seek, BinaryHeap, NonNull, and more.

This is just a quick recap. For more details, check out here

Have a great day

Francesco

Blog

Announcing Rust 1.80.0

Francesco Ciulla