title: generic type conforming to a protocol in Swift
body: <p>Is it possible to require that specific instantiations of generic types conform to a protocol in Swift?</p>
  
  <p>For example, say I have a generic type called <code>Thing&lt;T&gt;</code>. I want <code>Thing&lt;Int&gt;</code> to conform to a certain protocol, but not <code>Thing&lt;T&gt;</code>.</p>