Public Service Announcement.
If you are using any iOS plugins that use Swift v3 or less; DO NOT UPGRADE to XCode 10.2. Apple in its infinite wisdom has completly removed the Swift 3 tool chain.
You can re-add the tool chain back; BUT Apples guidelines state that apps submitted must be using the built in tool chain -- so odds would be very likely that if you re-added the Swift 3 tool chain to XCode 10.2, that the app would be rejected by Apple due to its requirements.
So the safest bet is to stay at XCode 10.1 if you are using any Swift plugins...