title: Django: using F() expressions on JSONField?
body: <p>I have the model</p>
  
  <pre><code>class Product(Model):
      properties = JSONField()
  </code></pre>
  
  <p>When querying </p>
  
  <pre><code>Product.objects.values('properties__color')
  </code></pre>
  
  <p>i'm getting the correct result </p>
  
  <blockquote>
    <p>SELECT product.properties->color FROM product</p>
  </blockquote>
  
  <p>However, when I'm doing what I thought to be equivalent</p>
  
  <pre><code>Product.objects.values(color=F('properties__color'))
  </code></pre>
  
  <p>the query that's executed is completely different</p>
  
  <blockquote>
    <p>SELECT product.properties AS color FROM product</p>
  </blockquote>
  
  <p>Is this a bug of django's JSONField, or have I misunderstood <code>F()</code> expressions?</p>