title: Why Kotlin modifier 'open' is incompatible with 'data'?
body: <p>I have a class:</p>
  
  <pre><code>open data class Person(var name: String)
  </code></pre>
  
  <p>and another class:</p>
  
  <pre><code>data class Student(var reg: String) : Person("")
  </code></pre>
  
  <p>this gives me an error that:</p>
  
  <blockquote>
    <p>error: modifier 'open' is incompatible with 'data'</p>
  </blockquote>
  
  <p>if I remove data from <code>Person</code> class it's fine.</p>
  
  <p>why kotlin open and data incompatible?</p>