error[E0594]: cannot assign to `*x`, which is behind a `&` reference
  --> $DIR/enum.rs:9:5
   |
LL |     *x += 1;
   |     ^^^^^^^ `x` is a `&` reference, so the data it refers to cannot be written

error[E0594]: cannot assign to `*x`, which is behind a `&` reference
  --> $DIR/enum.rs:13:9
   |
LL |         *x += 1;
   |         ^^^^^^^ `x` is a `&` reference, so the data it refers to cannot be written

error[E0594]: cannot assign to `*x`, which is behind a `&` reference
  --> $DIR/enum.rs:19:9
   |
LL |         *x += 1;
   |         ^^^^^^^ `x` is a `&` reference, so the data it refers to cannot be written

error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0594`.