title: Why is --isolatedModules error fixed by any import?
body: <p>In a create-react-app typescript project, I tried to write this just to test some stuff quickly:</p>
  
  <pre class="lang-js prettyprint-override"><code>// experiment.test.ts
  it('experiment', () =&gt; {
    console.log('test');
  });
  </code></pre>
  
  <p>But it gives me the following error, with a red squiggly beneath <code>it</code>:</p>
  
  <blockquote>
    <p>All files must be modules when the '--isolatedModules' flag is provided.</p>
  </blockquote>
  
  <p>However, if I change the file to the following, then everything apparently is fine (except for the unused import of course):</p>
  
  <pre class="lang-js prettyprint-override"><code>// experiment.test.ts
  import { Component} from 'react'; // literally anything, don't even have to use it
  
  it('test', () =&gt; {
    console.log('test');
  });
  </code></pre>
  
  <p>Why? What is happening here? What does <code>--isolatedModules</code> actually mean/do?</p>