title: Arrow function in typescript interface with return type as void
body: <p>I am trying to write arrow function in my type Script interface as below but getting error <strong>"Class 'ToastrService' incorrectly implements interface 'IToastr'."</strong></p>
  
  <pre><code>interface IToastr{
      (message:string,title:string):void;
  }
  
  @Injectable()
  export class ToastrService implements IToastr {
      (message:string,title:string):void {
           toastr.success(message,title);
      }
  }
  </code></pre>
  
  <p>My question is:  can we define a function signature in TS interface with return type as void??</p>
  
  <p>I did try searching google as well but did not find any example. Thanks !!</p>