static IntRange addToIntRange(IntRange r, int val) {
  if (r == null || r.empty())
    ret new IntRange(val, val+1);
  if (val < r.start) ret intRange(val, r.end);
  if (val >= r.end) ret intRange(r.start, val+1);
  ret r;
}

Began life as a copy of #1005874