Flutter 颤振-使用冻结包的序列化不起作用

请参阅以下代码

part 'order.g.dart';
part 'order.freezed.dart';
@freezed
abstract class Order with _$Order{
  const factory Order({List<Item> items}) = _Order;
  factory Order.fromJson(Map<String,dynamic> json) => _$OrderFromJson(json);
}

获取以下异常：

type '_$_Item' is not a subtype of type 'Map<String, dynamic>' in type cast
When the exception was thrown, this was the stack:
#0      _$_$_OrderFromJson.<anonymous closure> 
package:test7/order.g.dart:13
#1      MappedListIterable.elementAt  (dart:_internal/iterable.dart:417:31)
#2      ListIterator.moveNext  (dart:_internal/iterable.dart:343:26)
#3      new List.from  (dart:core-patch/array_patch.dart:38:29)
#4      new List.of  (dart:core-patch/array_patch.dart:68:17)
#5      ListIterable.toList  (dart:_internal/iterable.dart:211:44)

类型“\u$\ u Item”不是类型转换中类型“Map”的子类型
引发异常时，这是堆栈：
#0$\u$\ uOrderFromJSON。
包装：test7/订单.g.dart:13
#1 MappedListIterable.elementAt（省道：内部/省道：417:31）
#2 ListIterator.moveNext（dart:_internal/iterable.dart:343:26）
#3新列表。起始（dart:核心补丁/阵列补丁。dart:38:29）
#4.新列表（dart:core patch/array_patch.dart:68:17）
#5 ListIterable.toList（省道：内部/省道：211:44）

这是否意味着我们不能在@freezed对象中使用类似集合的列表

    var order = Order(items: [Item(name:' aSasaS')]);
    print(order.toJson().toString());
    final o = Order.fromJson(order.toJson());
    print('all done');

type '_$_Item' is not a subtype of type 'Map<String, dynamic>' in type cast
When the exception was thrown, this was the stack:
#0      _$_$_OrderFromJson.<anonymous closure> 
package:test7/order.g.dart:13
#1      MappedListIterable.elementAt  (dart:_internal/iterable.dart:417:31)
#2      ListIterator.moveNext  (dart:_internal/iterable.dart:343:26)
#3      new List.from  (dart:core-patch/array_patch.dart:38:29)
#4      new List.of  (dart:core-patch/array_patch.dart:68:17)
#5      ListIterable.toList  (dart:_internal/iterable.dart:211:44)