error: variable does not need to be mutable
  --> $DIR/capture-mut-ref.rs:9:9
   |
LL |     let mut x = &mut 0;
   |         ----^
   |         |
   |         help: remove this `mut`
   |
note: the lint level is defined here
  --> $DIR/capture-mut-ref.rs:6:9
   |
LL | #![deny(unused_mut)]
   |         ^^^^^^^^^^

error: aborting due to previous error