anchor.diff:    ///
     /// Like [parse] except that this function returns `null` where a
     /// similar call to [parse] would throw a [FormatException].
  +  ///
  +  /// Example:
  +  /// ```dart
  +  /// print(int.tryParse('2021')); // 2021
  +  /// print(int.tryParse('1f')); // null
  +  /// // From binary (base 2) value.
  +  /// print(int.tryParse('1100', radix: 2)); // 12
  +  /// print(int.tryParse('00011111', radix: 2)); // 31
  +  /// print(int.tryParse('011111100101', radix: 2)); // 2021
  +  /// // From octal (base 8) value.
  +  /// print(int.tryParse('14', radix: 8)); // 12
  +  /// print(int.tryParse('37', radix: 8)); // 31
  +  /// print(int.tryParse('3745', radix: 8)); // 2021
  +  /// // From hexadecimal (base 16) value.
  +  /// print(int.tryParse('c', radix: 16)); // 12
  +  /// print(int.tryParse('1f', radix: 16)); // 31
  +  /// print(int.tryParse('7e5', radix: 16)); // 2021
  +  /// // From base 35 value.
  +  /// print(int.tryParse('y1', radix: 35)); // 1191 == 34 * 35 + 1
  +  /// print(int.tryParse('z1', radix: 35)); // null
  +  /// // From base 36 value.
  +  /// print(int.tryParse('y1', radix: 36)); // 1225 == 34 * 36 + 1
  +  /// print(int.tryParse('z1', radix: 36)); // 1261 == 35 * 36 + 1
  +  /// ```
     external static int? tryParse(String source, {int? radix});
   }
  
positive.code:   ///
    /// Instead of throwing and immediately catching the [FormatException],
    /// instead use [tryParse] to handle a parsing error.
    /// Example:
    /// ```dart
    /// var value = int.tryParse(text);
  
negative.code:   /// Converts [this] to a string representation in the given [radix].
    ///
    /// In the string representation, lower-case letters are used for digits above
    /// '9', with 'a' being 10 and 'z' being 35.
    ///
    /// The [radix] argument must be an integer in the range 2 to 36.
    ///
    /// Example:
    /// ```dart
    /// // Binary (base 2).
    /// print(12.toRadixString(2)); // 1100
    /// print(31.toRadixString(2)); // 11111
    /// print(2021.toRadixString(2)); // 11111100101
    /// print((-12).toRadixString(2)); // -1100
    /// // Octal (base 8).
    /// print(12.toRadixString(8)); // 14
    /// print(31.toRadixString(8)); // 37
    /// print(2021.toRadixString(8)); // 3745
    /// // Hexadecimal (base 16).
    /// print(12.toRadixString(16)); // c
    /// print(31.toRadixString(16)); // 1f
    /// print(2021.toRadixString(16)); // 7e5
    /// // Base 36.
    /// print((35 * 36 + 1).toRadixString(36)); // z1
    /// ```
    String toRadixString(int radix);
  
    /// Parse [source] as a, possibly signed, integer literal and return its value.
  