anchor.diff:      String parameterName,
       void Function(DartEditBuilder builder) writeArgumentValue,
     ) {
  -    if (virtualContainer._parentCreation != null) {
  +    final virtualContainer = this.virtualContainer;
  +    if (virtualContainer == null) {
  +      return;
  +    }
  +    var parentCreation = virtualContainer._parentCreation;
  +    if (parentCreation != null) {
         // `new Padding(...)` -> `Container(...)`
         builder.addReplacement(
           range.startEnd(
  -          virtualContainer._parentCreation,
  -          virtualContainer._parentCreation.constructorName,
  +          parentCreation,
  +          parentCreation.constructorName,
           ),
           (builder) {
             builder.writeReference(virtualContainer.containerElement);
  
positive.code: // Copyright (c) 2019, 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.
  
  // @dart = 2.9
  
  import 'package:analysis_server/src/protocol_server.dart' as protocol;
  import 'package:analysis_server/src/services/flutter/class_description.dart';
  
negative.code:   final PropertyDescription property;
  
    /// The constructor `EdgeInsets.only`.
    ConstructorElement? onlyConstructor;
  
    double? leftValue;
    double? topValue;
    double? rightValue;
    double? bottomValue;
  
    PropertyDescription? leftProperty;
    PropertyDescription? topProperty;
    PropertyDescription? rightProperty;
    PropertyDescription? bottomProperty;
  
    _EdgeInsetsProperty(this.classEdgeInsets, this.property);
  
    Flutter? get flutter => property.flutter;
  
    void addNested() {
      Expression? leftExpression;
      Expression? topExpression;
      Expression? rightExpression;
      Expression? bottomExpression;
      var propertyExpression = property.valueExpression;
      if (propertyExpression is InstanceCreationExpression) {
        final flutter = this.flutter;
        var constructor = propertyExpression.constructorName.staticElement;
        if (flutter != null &&
            constructor != null &&
            constructor.enclosingElement == classEdgeInsets) {
          var arguments = propertyExpression.argumentList.arguments;
          var constructorName = constructor.name;
          if (constructorName == 'all') {
            var expression = flutter.argumentByIndex(arguments, 0);
            leftExpression = expression;
            topExpression = expression;
            rightExpression = expression;
            bottomExpression = expression;
          } else if (constructorName == 'fromLTRB') {
            leftExpression = flutter.argumentByIndex(arguments, 0);
            topExpression = flutter.argumentByIndex(arguments, 1);
            rightExpression = flutter.argumentByIndex(arguments, 2);
            bottomExpression = flutter.argumentByIndex(arguments, 3);
          } else if (constructorName == 'only') {
            var leftArgument = flutter.argumentByName(arguments, 'left');
            var topArgument = flutter.argumentByName(arguments, 'top');
            var rightArgument = flutter.argumentByName(arguments, 'right');
  