Review

class MustBeReachingVariableDef.Definition {
    @Override
    public boolean equals(Object other) {
      if (!(other instanceof Definition)) {
        return false;
      }
      Definition otherDef = (Definition) other;
      // If the var has the same definition node we can assume they have the
      // same depends set.
      return otherDef.node == node;
    }
}

class MustBeReachingVariableDef.MustDef {
    @Override
    public boolean equals(Object other) {
      return (other instanceof MustDef) &&
          ((MustDef) other).reachingDef.equals(this.reachingDef);
    }

}