anchor.diff:  class PreferFinalFields extends LintRule implements NodeLintRule {
     PreferFinalFields()
         : super(
  -      name: 'prefer_final_fields',
  -      description: _desc,
  -      details: _details,
  -      group: Group.style);
  +            name: 'prefer_final_fields',
  +            description: _desc,
  +            details: _details,
  +            group: Group.style);
   
     @override
     void registerNodeProcessors(NodeLintRegistry registry,
  
positive.code: }
  
  bool _containedInInitializer(
      Element element, ConstructorInitializer initializer) =>
      initializer is ConstructorFieldInitializer &&
          DartTypeUtilities.getCanonicalElementFromIdentifier(
              initializer.fieldName) ==
              element;
  
  bool _containedInFormal(Element element, FormalParameter formal) =>
      formal is FieldFormalParameter &&
          formal.declaredElement.toString() == element.toString();
  
negative.code: 
    void _addMutatedFieldElement(Expression expression) {
      final element =
          DartTypeUtilities.getCanonicalElementFromIdentifier(expression);
      if (element is FieldElement) {
        _mutatedFields.add(element);
      }
  