title: How to export multiple Type Aliases?
body: <p>For better capsulation I want to create a new type that includes multiple other types. <code>entityService</code> should be typed as <code>OakService</code> or <code>MapleService</code> which should be included inside <code>TreeService</code>.</p>
  
  <p>One possible solition you can see inside the comments. If I uncomment the imports inside <strong>garden.component.ts</strong> and replace <code>TreeService</code> with <code>OakService | MapleService</code>, it will work, but I want some kind of parent type, that includes them all.</p>
  
  <p><strong>tree.service.ts</strong></p>
  
  <pre><code>import { OakService } from './oak.service';
  import { MapleService } from './maple.service';
  
  export type TreeService = typeof OakService | MapleService;
  </code></pre>
  
  <p><strong>oak.service.ts</strong></p>
  
  <pre><code>import { BaseService } from './base.service';
  
  @Injectable()
  export class OakService extends BaseService {
    constructor() {
      super();
    }
  }
  </code></pre>
  
  <p><strong>maple.service.ts</strong></p>
  
  <pre><code>import { BaseService } from './base.service';
  
  @Injectable()
  export class MapleService extends BaseService {
    constructor() {
      super();
    }
  }
  </code></pre>
  
  <p><strong>garden.component.ts</strong></p>
  
  <pre><code>// import { OakService } from './oak.service';
  // import { MapleService } from './maple.service';
  import { TreeService } from './parent.service';
  
  @Component()
  export class GardenComponent {
    constructor(
      protected entityService: TreeService // OakService | MapleService
    ) {}
  }
  </code></pre>
  
  <p><strong>balcony.component.ts</strong></p>
  
  <pre><code>import { MapleService } from './maple.service';
  
  export class BalconyComponent extends GardenComponent {   
    constructor(
      protected mapleService: MapleService
    ) {
      super(mapleService);   
    }
  }
  </code></pre>
  
  <blockquote>
    <p><strong>Info:</strong> The code above does not work. Your have to use the code inside the comments. The error I've got is not inside <strong>balcony.component.ts</strong>:
    <em>ERROR in : Can't resolve all parameters for BaseListComponent in .../garden.component.ts: (?).</em></p>
  </blockquote>