anchor.diff:      return nested;
     }
   
  -  String _expressionCode(Expression expression) {
  +  String? _expressionCode(Expression? expression) {
       if (expression != null) {
  -      var content = property.resolvedUnit.content;
  +      var content = property.resolvedUnit.content!;
         return content.substring(expression.offset, expression.end);
       }
       return null;
     }
   
  -  static protocol.FlutterWidgetPropertyValue _protocolValueDouble(
  -    double value,
  -  ) {
  +  static protocol.FlutterWidgetPropertyValue? _protocolValueDouble(
  +      double? value) {
       if (value != null) {
         return protocol.FlutterWidgetPropertyValue(
           doubleValue: value,
  
positive.code: 
      var builder = ChangeBuilder(session: property.resolvedUnit.session);
  
      await builder.addDartFileEdit(property.resolvedUnit.path, (builder) {
        property._changeCode(builder, (builder) {
          if (leftCode == rightCode && topCode == bottomCode) {
            builder.writeReference(classEdgeInsets);
  
negative.code:       return '${value.intValue}';
      }
  
      code = value.stringValue;
      if (code != null) {
        if (code.contains("'")) {
          code = code.replaceAll("'", r"\'");
        }
  