error[E0594]: cannot assign to `self.foo`, which is behind a `&` reference --> $DIR/issue-93093.rs:8:9 | LL | self.foo += 1; | ^^^^^^^^^^^^^ `self` is a `&` reference, so the data it refers to cannot be written | help: consider changing this to be a mutable reference | LL | async fn bar(&mut self) { | ~~~~~~~~~ error: aborting due to previous error For more information about this error, try `rustc --explain E0594`.