error[E0308]: mismatched types
  --> $DIR/slice-mut.rs:7:22
   |
LL |     let y: &mut[_] = &x[2..4];
   |            -------   ^^^^^^^^ types differ in mutability
   |            |
   |            expected due to this
   |
   = note: expected mutable reference `&mut [_]`
                      found reference `&[isize]`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0308`.