Rust 1.80 的新特性

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));    });}

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

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`

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",    }}

$ rustup update stable