title: How to specify duck typing (implicit interface) generics in Kotlin?
body: <p>For example</p>
  
  <pre><code>// Not valid Kotlin code.
  fun &lt;T : Summable&gt; myFunction ...
  </code></pre>
  
  <p><code>T : Summable</code> means any type <code>T</code> supports <code>+</code> operator, i.e. has a <code>.plus</code> method defined.</p>