1 error[E0596]: cannot borrow `x.0` as mutable, as `x` is not declared as mutable
2 --> $DIR/borrowck-ref-mut-of-imm.rs:4:12
4 LL | fn destructure(x: Option<isize>) -> isize {
5 | - help: consider changing this to be mutable: `mut x`
7 LL | Some(ref mut v) => *v
8 | ^^^^^^^^^ cannot borrow as mutable
10 error: aborting due to previous error
12 For more information about this error, try `rustc --explain E0596`.