error: the `wait` method cannot be invoked on a trait object --> $DIR/issue-35976.rs:20:9 | LL | fn wait(&self) where Self: Sized; | ----- this has a `Sized` requirement ... LL | arg.wait(); | ^^^^ | help: another candidate was found in the following trait, perhaps add a `use` for it: | LL | use private::Future; | error: aborting due to previous error