sclass SizeEstimate {
  new Map<S, Long> shallowFieldSizes;
  new Set<S> complexFields;
  new Map<S, Long> complexFieldSizes;
}

static SizeEstimate estimateWebBotSize(O o) {
  new SizeEstimate se;
  Collection<S> fields = fields(o);
  for (S field : fields) {
    if (sizeCalculation_shouldIgnoreProgramField(field)) continue;
    O value = get(o, field);
    if (value == null) continue;
    Class type = value.getClass();
    if (isBoxedType(type) || isPrimitiveArray(value))
      continue with se.shallowFieldSizes.put(field, deepObjectSize(value));
    se.complexFields.add(field);
  }
  
  O[] array = asObjectArray(getFields(o, se.complexFields));
  new guessDeepObjectSize_recursive_Data data;
  data.seen.add(o);
  ret guessDeepObjectSize_recursive(data, array)-inMemorySizeOfArray(array);
}

Began life as a copy of #1024089