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blog.rust-lang.org
  • sugar_in_your_tea@sh.itjust.works
    1·
    6 days ago

    HashMaps and slices now support indexing multiple elements mutably

    This is kinda neat. I was hoping for something more generic, so hopefully this is a step toward that.

    Allow safe functions to be marked with the #[target_feature] attribute.

    This seems huge for library authors! That’s not me as of yet, but maybe soon. 😀

    Congrats on the release!

  • livingcoder@programming.dev
    14·
    26 days ago

    Wow, that trait feature is great. I’ve been eagerly waiting for that one for a long time. Thank you to everyone who made that possible.

    • INeedMana@lemmy.world
      1·
      21 days ago

      If a trait has a supertrait you can coerce a reference to said trait object to a reference to a trait object of the supertrait

      As someone that just started learning Rust: wha?

      • livingcoder@programming.dev
        3·
        21 days ago

        Basically, you can generalize your trait types into their parent (super) traits for situations when functionality is specific to those supertrait objects.

        As an example, if you have a trait CanBark and it is a super trait for the trait IsDog, you can coerce your references of &dyn IsDog into a &dyn CanBark. You can then work with other trait types that share a super trait.

        trait CanBark {
    fn bark(&self);
}
trait IsSeal: CanBark { }
trait IsDog: CanBark { }

fn bark_as_group(barkers: &Vec<&dyn CanBark>) {
    for barker in barkers {
        barker.bark();
    }
}

let spot: &dyn IsDog = get_spot();
let seal: &dyn IsSeal = get_seal();
let barkers: Vec<&dyn CanBark> = Vec::new();
barkers.push(spot);  // coerced
barkers.push(seal);  // coerced
bark_as_group(&barkers);

        At least, I hope this is possible now. If it’s purely “you can return a coerced type from a function”, that is less useful.