code: static UtilEvalError castError(
          Class lhsType, Class rhsType, int operation   )
      {
          return castError(
              StringUtil.typeString(lhsType),
              StringUtil.typeString(rhsType), operation  );
      }
docs: Return a UtilEvalError or UtilTargetError wrapping a ClassCastException
  describing an illegal assignment or illegal cast, respectively.