code: private boolean validRawTypeOfTypeExpression(Node expr) {
      // The expression must have two children. The rawTypeOf keyword and the
      // parameter
      if (!checkParameterCount(expr, Keywords.RAWTYPEOF)) {
        return false;
      }
      // The parameter must be a valid type expression
      if (!validTypeTransformationExpression(getCallArgument(expr, 0))) {
        warnInvalidInside(Keywords.RAWTYPEOF.name, expr);
        return false;
      }
      return true;
    }
docs: A raw type expression must be of the form rawTypeOf(TTLExp)