anchor.diff:      帮助我们将一个应用程序组织成内聚的功能模块群。
       一个 Angular 模块标识应用程序使用的组件、指令和管道等，还包含应用程序需要的外部 Angular 模块的列表，例如`FormsModule`。
       
  -    Every Angular application has an application root -module class. By convention, the class is
  +    Every Angular application has an application root-module class. By convention, the class is
       called `AppModule` and resides in a file named `app.module.ts`.
   
       每个 Angular 应用程序都有一个应用程序根模块类。按规约这个类的名字为`AppModule`，存放在名为`app.module.ts`的文件。
  
positive.code:     Without a barrel, a consumer needs three import statements:
      
      如果没有封装桶，消费者需要三条导入语句：  
    code-example.
      import { HeroComponent } from '../heroes/hero.component.ts';
      import { Hero }          from '../heroes/hero.model.ts';
  
negative.code:       ```@Component({...})
        export class AppComponent {
          constructor(@Inject('SpecialFoo') public foo:Foo) {}
          @Input() name:string;
        }
        ```
        
        The scope of a decorator is limited to the language feature
  