error[E0596]: cannot borrow data in a `&` reference as mutable --> $DIR/dont-print-desugared-async.rs:5:20 | LL | async fn async_fn(&ref mut s: &[i32]) {} | ^^^^^^^^^ cannot borrow as mutable through `&` reference error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0596`.