struct Link;
typedef sequence<Link> DescendantSeq;

union uLink;
typedef sequence<uLink> uDescendantSeq;

struct Link {
  short some_value;
  DescendantSeq descendants;
  uDescendantSeq udescendants;
};

union uLink switch (boolean) {
case TRUE:
  DescendantSeq descendants;
case FALSE:
  uDescendantSeq udescendants;
};