error[E0505]: cannot move out of `x.0` because it is borrowed
  --> $DIR/guard-lifetime-1.rs:8:14
   |
LL |         Some(mut y) if let Some(ref z) = y => {
   |              ^^^^^
   |              |
   |              move out of `x.0` occurs here
   |              borrow of `x.0` occurs here
LL |
LL |             let _z: &String = z;
   |                               - borrow later used here

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0505`.