title: abstract class constructor throws error
body: <p>I have an abstract class where I mentioned all my <code>http</code> calls and while extending it in child services throws error on compile time.</p>
  
  <blockquote>
    <p>Can't resolve all parameters for MyService : (?).</p>
  </blockquote>
  
  <p>baseservice.ts</p>
  
  <pre><code>import { HttpClient, HttpHeaders } from '@angular/common/http';
  
  export abstract class BaseService{
  
      constructor(private http: HttpClient){} //http undefined on compile time                            
  
      get(){
         return this.http.get()
      }    
  }
  </code></pre>
  
  <p>myservice.ts</p>
  
  <pre><code>@Injectable()
  export class MyService extends BaseService{
  
    getSource() {
      return this.get('api/Source')
    }
  }
  </code></pre>
  
  <p>If I added other injectTokens in constructor of abstract class this leads to <code>not defined</code> error</p>
  
  <pre><code>constructor(private http: HttpClient, @Inject(APP_CONFIG) private appConfig: any | undefined) {}
  </code></pre>
  
  <blockquote>
    <p>Uncaught ReferenceError: http_1 is not defined</p>
  </blockquote>
  
  <p>if I trying to add Options, it initialising the HttpClient and all working fine </p>
  
  <pre><code>HttpOptions = {
     headers: new HttpHeaders({
      'Authorization': `Bearer ${this.token}`
     })
  </code></pre>
  
  <p>What is the reason behind this and how to over come this issue while creating instance <code>HttpClient</code> without any <code>InjectTokens</code> or <code>httpOtions</code>.</p>