title: Refs with instance variable gives error
body: <p>I have a React component that I'm migrating to <code>tsx</code> file and I'm getting an error <code>Property 'name' does not exist on type 'NameComponent'</code>.</p>
  
  <p>Here is my component:</p>
  
  <pre><code>class NameComponent extends React.Component&lt;NameComponentProps&gt; {
      render() {
          return (
              &lt;Modal&gt;
                  &lt;Modal.Header&gt;
                      Enter Name
                  &lt;/Modal.Header&gt;
                  &lt;Modal.Body&gt;
                      &lt;FormGroup&gt;
                          &lt;ControlLabel&gt;Name: &lt;/ControlLabel&gt;
                          &lt;FormControl type="text"
                              placeholder='Enter name'
                              inputRef={(ref) =&gt; this.name = ref}
                              onChange={() =&gt; this.props.onValidate({ name: this.name.value })}
                          /&gt;
                          &lt;FormControl.Feedback /&gt;
                      &lt;/FormGroup&gt;
                 &lt;/Modal.Body&gt;
              &lt;/Modal&gt;
          );
      }
  }
  </code></pre>
  
  <p>There is a red undeline on the occurences of <code>this.name</code>.  This worked back when I had this file in <code>.js</code> format. </p>
  
  <p>How do I resolve this error? </p>