svoid ai_parseTree_makeTotalWeights(PTElement e, double weight) {
  e.totalWeight = weight*e.weight;
  
  for (PTElement child : unnull(e.children))
    ai_parseTree_makeTotalWeights(child, e.totalWeight);
    
  // prefer composites if weight is the same
  // so we get the least casting on top
  sortInPlaceByCalculatedFieldDesc(e.children, func(PTElement e) -> Pair<Bool, Double> { pair(e instanceof ChoosePart, e.totalWeight) });
}