static SFormsFastMapDirect mergeMaps(SFormsFastMapDirect mapTo, SFormsFastMapDirect map2) {

    if (mapTo != map2 && map2 != null && !map2.isEmpty()) {
      mapTo.union(map2);
    }

    return mapTo;
  }
Merge the variable data from 2 maps.
@param mapTo The first map to merge. Will be mutated.
              The result will be stored in this map.
@param map2 The second map to merge. Will not be mutated. Nullable.
src/org/jetbrains/java/decompiler/modules/decompiler/sforms/VarMapHolder.java