title: exporting a default async function is not defined in current file
body: <p>The following works perfectly:</p>
  
  <pre><code>export default function x () {
    return 'hello world'
  }
  
  export function y () {
    return x()
  }
  
  console.log(y())
  </code></pre>
  
  <p>However this does not work:</p>
  
  <pre><code>export default async function x () {
    return 'hello world'
  }
  
  export function y () {
    return x()
      .then(console.log)
  }
  
  y()
  </code></pre>
  
  <p>When the <code>default</code> function is <code>async</code> for some reason <code>x is not defined</code>.</p>