Announcing async fn and return-position impl Trait in traits

Aaaw yiiiss, been waiting for this, -> impl xxx simplifies function signatures soo much, so not being allowed to do that in traits was a real pain

    
trait HttpService {
    async fn fetch(&self, url: Url) -> HtmlBody;
//  ^^^^^^^^ desugars to:
//  fn fetch(&self, url: Url) -> impl Future;
}


  

Man I've been waiting for this to be stabilized for a long time. So excited about it.