anchor.diff:      }
   
       @override
  -    double parse(String value) => double.parse(value);
  +    double _doParse(String value) => double.parse(value);
   }
   
   class IntValidatorFactory extends NumberValidatorFactory<int> {
  
positive.code: 
      Rule _maxRule(FieldOptions options) {
          var max = options.getExtension(Options.max) as MaxOption;
          var bound = parse(max.value);
          var exclusive = max.exclusive;
          var literal = literalNum(bound);
          var check = exclusive
                      ? (Expression v) => v.greaterOrEqualTo(literal)
                      : (Expression v) => v.greaterThan(literal);
          var requiredString = newRule((v) => check(v), _outOfBound);
          return requiredString;
      }
      
      N parse(String value) => null;
  
      // TODO:2019-10-14:dmytro.dashenkov: Support custom error messages based on the option value.
      // https://github.com/SpineEventEngine/base/issues/482
  
negative.code:             Rule max = _maxRule(options);
              rules.add(max);
          }
          if (options.hasExtension(Options.range)) {
              Iterable<Rule> range = _rangeRules(options);
              rules.addAll(range);
          }
          return rules;
      }
  
      Rule _minRule(FieldOptions options) {
          var min = options.getExtension(Options.min) as MinOption;
          var bound = _parse(min.value);
          var exclusive = min.exclusive;
          return _constructMinRule(bound, exclusive);
      }
      
      Rule _constructMinRule(N bound, bool exclusive) {
          var literal = literalNum(bound);
          var check = exclusive
                      ? (Expression v) => v.lessOrEqualTo(literal)
  