Sorting Collections with `map` closures and SortDescriptors

[Ponyboy47 (Jacob Williams)]

@cal

My take is that KeyPath<Element, Value> could become interchangeable with (Element) -> Value , since they have the same semantic meaning.

This pitch was specifically about mapping with a KeyPath, but I personally agree that KeyPaths should be interchangeable with Elements since that's really all a KeyPath is doing. This should probably be part of its own pitch/proposal though...