anchor.diff:  /// Checks for duplicate section entries in the body of a section.
   Iterable<LintingError> lintSectionEntryDuplicates(StatusSection section) {
     var errors = <LintingError>[];
  -  // TODO(whereType): When whereType is supported, use that.
     List<StatusEntry> statusEntries = section.entries
  -      .where((entry) => entry is StatusEntry)
  -      .cast<StatusEntry>()
  +      .whereType<StatusEntry>()
         .toList();
     for (var i = 0; i < statusEntries.length; i++) {
       var entry = statusEntries[i];
  
positive.code: /// ordered alphabetically.
  Iterable<LintingError> lintAlphabeticalOrderingOfPaths(StatusSection section) {
    var entries = section.entries
        .where((entry) => entry is StatusEntry)
        .map((entry) => (entry as StatusEntry).path)
        .toList();
    var sortedList = entries.toList()..sort((a, b) => a.compareTo(b));
  
negative.code:     }
      return lintingErrors;
    }
    return section.entries.whereType<CommentEntry>().map((entry) =>
        new LintingError(entry.lineNumber, "Comment is on a line by itself."));
  }
  
  