message: Fix future-warning due to comparison with None::<X> with unspecified X
diff: @@ -257,11 +257,11 @@ mod tests {
  let all_doms: Vec<_> = doms.dominators(2).unwrap().collect();
  assert_eq!(vec![2, 1, 0], all_doms);
  - assert_eq!(None, doms.dominators(99).map(|_| unreachable!()));
  + assert_eq!(None::<()>, doms.dominators(99).map(|_| unreachable!()));
  let strict_doms: Vec<_> = doms.strict_dominators(2).unwrap().collect();
  assert_eq!(vec![1, 0], strict_doms);
  - assert_eq!(None, doms.strict_dominators(99).map(|_| unreachable!()));
  + assert_eq!(None::<()>, doms.strict_dominators(99).map(|_| unreachable!()));
  }
  }
  