Angular 2 angular-cli AOT在模块中声明抽象类？

我正在尝试使用angular-cli进行AOT编译设置.我有一个从抽象类继承的指令,我在编译期间遇到一个错误,即angular无法确定抽象类属于哪个模块.我无法将它添加到NgModule的声明数组中,那么正确的方法是什么呢？我的代码结构如下所示,

//...imports
export abstract class TutorialDirective  {
    //...base class logic
}

@Directive({
    selector: '[tut]',
    exportAs: 'tut'
})
export class DefaultTutorialDirective extends TutorialDirective {
    //...calls into the base class for some shared stuff.
}

错误看起来像这样

ERROR in Cannot determine the module for class TutorialDirective in /test-app/src/app/tutorial/directive/tutorial.directive.ts!

我的AppModule:

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { FormsModule } from '@angular/forms';
import { HttpModule } from '@angular/http';

import { AppComponent } from './app.component';

import { TutorialService } from './tutorial/tutorial.service';
import { TutorialDirective, DefaultTutorialDirective } from './tutorial/directive/tutorial.directive';

@NgModule({
  declarations: [
    AppComponent,
    DefaultTutorialDirective
  ],
  imports: [
    BrowserModule,
    FormsModule,
    HttpModule
  ],
  providers: [TutorialService],
  bootstrap: [AppComponent]
})
export class AppModule { }

好的经过一些调试,如果我把它变成抽象并将其添加到声明中就可以了.这是否意味着我不能将一个类标记为抽象？这似乎不对......

从抽象类中删除@Component装饰器,将其替换为@Injectable()装饰器.