flutter - 如何在通用Dart方法中对通用类型T实现强行实现约束？

我正在努力实现的目标
我正在尝试创建一个通用Dart方法，该方法采用通用类型T，其中T必须实现类IModel。然而，
问题
看来我不能在T类型上设置implements约束，而只能设置extends。例如，<T implements IModel不起作用，但是<T extends IModel>起作用。
码
IModel.dart作为接口(interface):

class IModel {
  IModel();

  factory IModel.fromJson(Map<String, dynamic> json) {
    return IModel();
  }

  Map<String, dynamic> toJson() => {};

  IModel clone() {
    return IModel();
  }
}

WorkControlPlanModel.dart，一个实现IModel的示例:

import 'dart:core';
import 'package:knowe_personnelledger_mobile/helpers/DateTimeHelper.dart';
import 'package:knowe_personnelledger_mobile/helpers/StringHelper.dart';
import 'package:knowe_personnelledger_mobile/models/IModel.dart';

class WorkControlPlanModel implements IModel {
  String id;
  String name;
  String companyId;
  String projectId;
  String description;
  DateTime created;
  DateTime updated;

  WorkControlPlanModel({this.id, this.name, this.description, this.created, this.updated, this.companyId, this.projectId});

  factory WorkControlPlanModel.fromJson(Map<String, dynamic> json) {
    return WorkControlPlanModel(id: json["id"], name: json["name"], created: DateTime.parse(json["created"]), updated: DateTime.parse(json["updated"]), description: json["description"], companyId: json["companyId"], projectId: json["projectId"]);
  }

  Map<String, dynamic> toJson() => {
        "Id": id,
        "Name": name,
        "Description": description,
        "CompanyId": companyId,
        "ProjectId": projectId,
        "Created": created.toIso8601String(),
        "Updated": updated.toIso8601String()
      };

  WorkControlPlanModel clone() {
    return new WorkControlPlanModel(id: StringHelper.clone(id), companyId: StringHelper.clone(companyId), created: DateTimeHelper.clone(created), updated: DateTimeHelper.clone(updated), name: StringHelper.clone(name), projectId: StringHelper.clone(projectId), description: StringHelper.clone(description));
  }
}

使用通用方法的ModelHelper.dart:

import 'dart:convert';

import 'package:knowe_personnelledger_mobile/models/IModel.dart';

// 'T implements IModel' not working, but 'T extends IModel' does as constraint.
abstract class ModelHelper {
  static List<T> listFromJson<T implements IModel>(String json) {
    List l = jsonDecode(json)["data"];
    var models = l.map((m) => T.fromJson(m)).toList();
    return models;
  }
}

其他问题/结论
Dart不支持implements约束吗？是否所有T类都只需要扩展IModel？

最佳答案

这不是问题。即使对于实现<T extends IModel>的类，您也可以安全地使用IModel:

abstract class Abstract {}

class Concrete implements Abstract {}

void function<T extends Abstract>(T value) {
  print(value);
}

void main() {
  function<Concrete>(Concrete()); // works
}