title: Injected Service in HttpInterceptor not initialized
body: <p>I am trying to inject a service into an HttpInterceptor, here is the simple service</p>
  
  <pre><code>import { Injectable } from '@angular/core';
  @Injectable()
  export class LoginLoadingService {
     constructor() { }
     public loaded: boolean;
     isLoaded() {
         if (this.loaded === undefined) {
               this.loaded = true;
         }
         return this.loaded;
    }    
  }
  </code></pre>
  
  <p>And the interceptor</p>
  
  <pre><code>import { HttpRequest, HttpHandler, HttpEvent, HttpInterceptor } from 
  '@angular/common/http';
  import { Injectable, Inject } from '@angular/core';
  import { Observable } from 'rxjs/Observable';
  import { LoginLoadingService } from './loading.service';
  import 'rxjs/add/operator/do';
  @Injectable()
  export class LoginLoadingInterceptor implements HttpInterceptor {
    constructor(public loginLoadingService: LoginLoadingService) { }
    intercept(req: HttpRequest&lt;any&gt;, next: HttpHandler): Observable&lt;HttpEvent&lt;any&gt;&gt; {
      this.loginLoadingService.loaded = false
      return next.handle(req).do((event: HttpEvent&lt;any&gt;) =&gt; {
        this.loginLoadingService.loaded = true;
      }, error =&gt; console.error(error));
    }
  }
  </code></pre>
  
  <p>And in my app.module</p>
  
  <pre><code>providers: [
    LoginLoadingService,
    {
      provide: HTTP_INTERCEPTORS,
      useClass: LoginLoadingInterceptor,
      multi: true
    }
  ]
  </code></pre>
  
  <p>The HttpInterceptor is firing fine, but the loginLoadingService is not defined in the intercept() method. I tried to add deps to the interceptor in app.module, but that gave me this error</p>
  
  <blockquote>
    <p>params.map is not a function</p>
  </blockquote>
  
  <p>Not sure what the issue is here</p>