anchor.diff:  bool isInt(x) => x is int;
   
   
  -bool isIntRes(x) {
  +int isIntRes(x) {
     if (x is int) {
       return 1;
     } else {
  
positive.code: bool isString(x) => x is String;
  
  
  bool isStringRes(x) {
    if (x is String) {
      return 1;
    } else {
  
negative.code: }
  
  
  int isNotStringRes(x) {
    if (x is! String) {
      return 1;
    } else {
  