docs: public int getCaseIndex(int accessor, String name) {
      JMFFieldDef field = getFieldDef(accessor);
      if (!(field instanceof JSVariant))
        return -1;
      JMFType target = findVariantChildByName((JSVariant)field, name);
      if (target != null)
        return getEffectiveSiblingPosition(target);
      else
        return -1;
    }