title: Angular service is referenced but not called, yet still "returns" correct value
body: <p><a href="https://plnkr.co/edit/MBEGkqnV5kie9PB3az9K?p=preview" rel="nofollow noreferrer">In this Plunk</a>, I've made a minor modification to the Angular.io tutorial.</p>
  
  <p>I've added a function to the heroes.service called <code>doHeroesExist</code>. 
  However, I never call it. The only thing I do it assign it to a variable in the <code>app.component</code></p>
  
  <pre><code>  ngOnInit(): void {
      //this.getHeroes();
      this.heroesExist = this.heroService.doHeroesExist;
      console.log("app ngOnInit called...", this.heroesExist);  // outputs: app ngOnInit called... true
    }
  </code></pre>
  
  <p>And here is the <code>doHeroesExist</code> function inside the <code>hero.service.ts</code> file.</p>
  
  <pre><code>  doHeroesExist(): boolean {
      console.log("doHeroesExist called..", this.doHeroesExist);
      return this.doHeroesExist;
    }
  </code></pre>
  
  <p>I am puzzled. </p>
  
  <p>Why does it say <strong>true</strong> in the console log? Shouldn't it output the body of the function as string? Also the console.log inside the <code>doHeroesExist</code> is never printed - further proof it's not called!</p>