anchor.diff:  class IndexError extends ArgumentError implements RangeError {
     /** The indexable object that [index] was not a valid index into. */
     final indexable;
  -  /** The invalid index. */
  -  final int invalidValue;
     /** The length of [indexable] at the time of the error. */
     final int length;
   
  
positive.code:  * Error thrown due to an index being outside a valid range.
   */
  class RangeError extends ArgumentError {
    /** The value that is outside its valid range. */
    final num invalidValue;
    /** The minimum value that [value] is allowed to assume. */
    final num start;
    /** The maximum value that [value] is allowed to assume. */
  
negative.code: 
    String toString() {
      if (!_hasValue) {
        var result = "Invalid arguments(s)";
        if (message != null) {
          result = "$result: $message";
        }
        return result;
      }
      String nameString = "";
      if (name != null) {
  