1 error[E0596]: cannot borrow immutable local variable `v` as mutable
2 --> $DIR/issue-33819.rs:13:39
4 LL | Some(ref v) => { let a = &mut v; },
5 | ^ cannot borrow mutably
7 error: aborting due to previous error
9 For more information about this error, try `rustc --explain E0596`.