anchor.diff:      // We force the hash codes to be unsigned 30-bit integers to avoid
       // issues with problematic keys like '__proto__'. Another option
       // would be to throw an exception if the hash code isn't a number.
  -    return JS('int', '# & 0x3ffffff', _hashCode(key));
  +    return JS('int', '# & #', _hashCode(key), _mask30);
     }
   
     int _findBucketIndex(var bucket, var key) {
  
positive.code:     // issues with problematic elements like '__proto__'. Another
      // option would be to throw an exception if the hash code isn't a
      // number.
      return JS('int', '# & 0x3ffffff', _hasher(element));
    }
  
    bool add(E object) => super._add(object);
  
negative.code:     // issues with problematic elements like '__proto__'. Another
      // option would be to throw an exception if the hash code isn't a
      // number.
      return JS('int', '# & #', element.hashCode, _mask30);
    }
  
    static bool _hasTableEntry(var table, var key) {
  