title: How to use `<script setup>`?
body: <p>Vue version: <code>3.0.11</code></p>
  <p>With the following code:</p>
  <pre class="lang-html prettyprint-override"><code>&lt;template&gt;
    &lt;button @click=&quot;inc&quot;&gt;{{ count }}&lt;/button&gt;
  &lt;/template&gt;
  
  &lt;script setup&gt;
    import { ref } from 'vue'
  
    export const count = ref(0)
  
    export const inc = () =&gt; count.value++
  &lt;/script&gt;
  </code></pre>
  <p>I got:</p>
  <pre class="lang-sh prettyprint-override"><code>ERROR  Failed to compile with 1 error
   error  in ./src/views/HyperScript.vue?vue&amp;type=script&amp;setup=true&amp;lang=js
  
  Syntax Error: TypeError: Cannot read property 'content' of null
  
  
   @ ./src/views/HyperScript.vue?vue&amp;type=script&amp;setup=true&amp;lang=js 1:0-293 1:0-293 1:294-576 1:294-576
   @ ./src/views/HyperScript.vue
   @ ./src/router/index.ts
   @ ./src/main.ts
   @ multi (webpack)-dev-server/client?http://192.168.6.175:8080&amp;sockPath=/sockjs-node (webpack)/hot/dev-server.js ./src/main.ts
  </code></pre>