anchor.diff:  // Copyright (c) 2015, the Dart project authors. Please see the AUTHORS file
   // for details. All rights reserved. Use of this source code is governed by a
   // BSD-style license that can be found in the LICENSE file.
  -
  -import 'dart:collection';
   
   import 'package:analyzer/dart/analysis/features.dart';
   import 'package:analyzer/error/error.dart';
  
positive.code:           String? value;
            if (k is YamlScalar) {
              value = toUpperCase(k.value);
              if (!errorCodes.contains(value) && !lintCodes.contains(value)) {
                reporter.reportErrorForSpan(
                    AnalysisOptionsWarningCode.UNRECOGNIZED_ERROR_CODE,
                    k.span,
  
negative.code:   static final String legalValueString =
        StringUtilities.printListOfQuotedNames(legalValues);
  
    /// Lazily populated set of error codes.
    static final Set<String> _errorCodes =
        errorCodeValues.map((ErrorCode code) => code.name).toSet();
  
    /// Lazily populated set of lint codes.
    late final Set<String> _lintCodes = Registry.ruleRegistry.rules
        .map((rule) => rule.name.toUpperCase())
        .toSet();
  
    @override
    void validate(ErrorReporter reporter, YamlMap options) {
  