docs: @Nullable
    private static SoyType getSoyTypeFromUnionForBinaryOperator(
        UnionType t0, SoyType t1, boolean isNullable, SoyTypeBinaryOperator operator) {
      List<SoyType> subTypes = new ArrayList<>();
      for (SoyType unionMember : t0.getMembers()) {
        SoyType result = getSoyTypeForBinaryOperator(unionMember, t1, operator);
        if (result == null) {
          return null;
        }
        subTypes.add(result);
      }
      SoyType result = UnionType.of(subTypes);
      return isNullable ? makeNullable(result) : result;
    }