title: In Racket, how to get and set an object's field as if it was a local variable?
body: <p>I want to do something like this:</p>
  
  <pre><code>(define-field-magic color car)
  (set! color "green")
  (pretty-display color)
  </code></pre>
  
  <p>Instead of this:</p>
  
  <pre><code>(set-field! color car "green")
  (pretty-display (get-field color car))
  </code></pre>