Yes, I've cleaned multiple times. I've actually been "battling" this issue for a couple of days now and I did see this problem, but I hadn't seen the solution to it. I do have two places where a protocol is constrained with Self: Some Class, so I removed both of them to test, but that unfortunately didn't help. SegFault again. I see that a lot of people seem to be experiencing SegFault due to different kinds of issues, e.g. https://bugs.swift.org/browse/SR-13800?jql=ORDER%20BY%20created%20DESC%2C%20creator%20DESC I'm not sure what to do at this point.