anchor.diff:    }
   
     /**
  -   * Returns the last matching index in [sequence] starting at [start]
  -   * (inclusive). Returns -1 if it could not be found.
  +   * Returns the first matching index in [sequence], searching backward
  +   * starting at [start] (inclusive). Returns -1 if it could not be found.
      */
     int lastIndexIn(String sequence, [int start]) {
       var codeUnits = sequence.codeUnits;
  
positive.code:   }
  
    /**
     * Returns the first matching index in [sequence], searching backward
     * starting at [start] (inclusive). Returns -1 if it could not be found.
     */
    int firstIndexIn(String sequence, [int start = 0]) {
      var codeUnits = sequence.codeUnits;
  
negative.code: /**
   * Abstract character matcher.
   *
   * The [CharMatcher] is a boolean predicate on characters. The inclusion of a
   * character can be determined by calling the matcher with the code-unit
   * of a character as the function argument, for example:
   *
   *     WHITESPACE(' '.codeUnitAt(0)); // true
   *     DIGIT('a'.codeUnitAt(0)); // false
  