The sum of types that can be used as a Quick Look representation.
Swift Standard Library
The PlaygroundQuickLook protocol is deprecated, and will be removed from the standard library in a future Swift release. To customize the logging of your type in a playground, conform to the CustomPlaygroundDisplayConvertible protocol, which does not use the PlaygroundQuickLook enum.
If you need to provide a customized playground representation in Swift 4.0 or Swift 3.2 or earlier, use a conditional compilation block: