title: Does the Swift "as" type casting operator keep the underlying memory intact?
body: <p>If I use &quot;as&quot; in all of it's forms... &quot;as?&quot;, &quot;as!&quot;... is there a guarantee that the underlying memory bits are not modified?</p>
  <p>For example when doing String as NSString, is there some runtime code that is executed in order to make the change possible or is the memory laid out in a way that no change is required, so there is no cost to the operation.</p>