anchor.diff:  // BSD-style license that can be found in the LICENSE file.
   
   library analyzer.src.task.options;
  +
  +import 'dart:collection';
   
   import 'package:analyzer/analyzer.dart';
   import 'package:analyzer/plugin/options.dart';
  
positive.code:       new List.from(AnalyzerOptions.ignoreSynonyms)
          ..addAll(AnalyzerOptions.includeSynonyms));
  
    bool recognizedErrorCode(String name) =>
        ErrorCode.values.any((ErrorCode code) => code.name == name) ||
            StaticInfo.names.contains(name);
  
    @override
    void validate(ErrorReporter reporter, Map<String, YamlNode> options) {
  
negative.code:       filters.nodes.forEach((k, v) {
          if (k is YamlScalar) {
            value = toUpperCase(k.value);
            if (!errorCodes.contains(value)) {
              reporter.reportErrorForSpan(
                  AnalysisOptionsWarningCode.UNRECOGNIZED_ERROR_CODE,
                  k.span,
  