sociated future's guarantees for all implementations of `` is an `async fn` in trait, which does not automatically imply that its future is `'x'3.14159Default::default()Ok(String::new()vec![] -> Result<(), Box> Ok(()) consider adding return typethis could be changed to `: ?Sized`...you could relax the implicit `Sized` bound on `` if it were used through indirection like `&` or `Box<