error[E0502]: cannot borrow `*a` as mutable because it is also borrowed as immutable --> $DIR/E0502.rs:4:5 | LL | let ref y = a; | ----- immutable borrow occurs here LL | bar(a); | ^^^^^^ mutable borrow occurs here LL | y.use_ref(); | - immutable borrow later used here error: aborting due to previous error For more information about this error, try `rustc --explain E0502`.