More directly, check out:
<a href="https:&#x2F;&#x2F;github.com&#x2F;apple&#x2F;swift&#x2F;blob&#x2F;master&#x2F;stdlib&#x2F;public&#x2F;core&#x2F;Policy.swift" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;apple&#x2F;swift&#x2F;blob&#x2F;master&#x2F;stdlib&#x2F;public&#x2F;cor...</a><p>Which is where much of the Swift &quot;language&quot; is defined... in the standard library.<p>-Chris