title: Argument of type 'Object' is not assignable to parameter of type 'string'
body: <p>My application works fine but I have the following error:</p>
  
  <blockquote>
    <p>Argument of type 'Object' is not assignable to parameter of type
    'string')</p>
  </blockquote>
  
  <p>Below my code:</p>
  
  <pre><code>public login(userData: any): Observable&lt;any&gt; {
      return this.http
        .post("/api/users/login", userData)
        .map(token =&gt; this.saveToken(token));
  }
  
  
  private saveToken(token: string): string {
      localStorage.setItem("car_auth", token);
      return token;
  }
  </code></pre>