error[E0502]: cannot borrow `y` as immutable because it is also borrowed as mutable --> $DIR/dropck-resume.rs:25:13 | LL | let z = &mut y; | ------ mutable borrow occurs here ... LL | r = y.as_ref().unwrap(); | ^ immutable borrow occurs here LL | LL | } | - mutable borrow might be used here, when `g` is dropped and runs the destructor for generator error: aborting due to previous error For more information about this error, try `rustc --explain E0502`.