error[E0596]: cannot borrow `data` as mutable, as it is not declared as mutable --> $DIR/issue-61187.rs:6:5 | LL | async fn response(data: Vec) { | ---- help: consider changing this to be mutable: `mut data` LL | data.reverse(); | ^^^^^^^^^^^^^^ cannot borrow as mutable error: aborting due to previous error For more information about this error, try `rustc --explain E0596`.