error[E0502]: cannot borrow `slice_1` as immutable because it is also borrowed as mutable
 --> compile_fail_tests/mut_lock_5.rs
  |
  |     let a = slice_1.iter_mut().next().unwrap();
  |             ------------------ mutable borrow occurs here
  |
  |     let element = slice_1.get(1).unwrap();
  |                   ^^^^^^^^^^^^^^ immutable borrow occurs here
  |
  |     a.borrow();
  |     ---------- mutable borrow later used here