this post was submitted on 21 Dec 2023
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Announcing async fn and return-position impl Trait in traits (blog.rust-lang.org)
submitted 11 months ago by clot27@lemm.ee to c/rust@programming.dev
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[–] sugar_in_your_tea@sh.itjust.works -1 points 11 months ago* (last edited 11 months ago)

-> impl Trait in public traits

That's a bummer. This works:

trait Base {
  fn op(&self);
}
trait Child : Base {
  fn other_op(&self);
}

trait A {
  fn some_fn(val: impl Base) {
    val.op();
  }
}

fn some_fn(val: impl Child) {
  val.op();
  val.other_op();
}

So it seems like returning an impl Child in a trait that binds impl Base should also work.

Hopefully this change means we'll see more of this kind of thing in the upcoming releases.