title: Accessing "form" property of a form ElementRef shows TypeScript error
body: <p>I have this form in my template:</p>
  
  <pre><code>&lt;form #heroForm="ngForm" (ngSubmit)="onSubmit()"&gt;
  </code></pre>
  
  <p>And I'm adding it as a ViewChild in the controller:</p>
  
  <pre><code>@ViewChild('heroForm') heroForm: ElementRef;
  </code></pre>
  
  <p>When I access the "form" property of it to see if it is valid, it shows a TypeScript error "Property 'form' does not exist on type 'ElementRef'.
  ".</p>
  
  <pre><code>if(this.heroForm.form.valid){
    this.submitted = true;
  }
  </code></pre>
  
  <p>How can I get rid of this error?</p>
  
  <p>Stackblitz example: <a href="https://stackblitz.com/edit/template-driven-form-demo-1tbb37?file=app%2Fuser-form%2Fuser-form.component.ts" rel="nofollow noreferrer">https://stackblitz.com/edit/template-driven-form-demo-1tbb37?file=app%2Fuser-form%2Fuser-form.component.ts</a></p>