It doesn&#x27;t look like they&#x27;ve opened any of the existing Foundation framework we all know and love and that&#x27;s written in Objective-C. The swift-corelib-foundation repo contains a bunch of .swift files, and those contain lots of calls to NSUnimplemented().<p>The Core Foundation stuff (included in swift-corelib-foundation) has been open for a while: <a href="http:&#x2F;&#x2F;www.opensource.apple.com&#x2F;source&#x2F;CF&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.opensource.apple.com&#x2F;source&#x2F;CF&#x2F;</a>