[jordansmithnz]

In general I’ve found protocol extensions to be an incredibly powerful concept. There’s a couple of WWDC talks about ‘protocol oriented programming’ that highlight some great, practical use cases.

I’ve run into the author’s problem a few times, and I’d like to think that this is just a bug or behaviour detail that a future Swift version could correct. Swift hasn’t quite matured fully yet, and this is a great example of that (these examples are becoming fewer every year though).