I've got this prefpane made in Swift and Cocoa... Yesterday I migrated it to Swift 4 as-per-the-migration guide and after some initial pains everything appeared to be working perfectly.
I did this on Sierra, running Xcode 9.0 with the latest SDK.
Problem is, at least two people running High Sierra tell me the pane is not running at all for them. From attempting to run it from the command line, this is the reported error:
2017-09-27 23:00:59.921 System Preferences[3047:337095] Error loading /Users/luckman212/Library/PreferencePanes/SwiftDefaultApps.prefPane/Contents/MacOS/SwiftDefaultApps: dlopen(/Users/luckman212/Library/PreferencePanes/SwiftDefaultApps.prefPane/Contents/MacOS/SwiftDefaultApps, 265): can't resolve symbol _OBJC_CLASS_$_NSError in /Users/luckman212/Library/PreferencePanes/SwiftDefaultApps.prefPane/Contents/MacOS/../Frameworks/libswiftCore.dylib because dependent dylib #1 could not be loaded in /Users/luckman212/Library/PreferencePanes/SwiftDefaultApps.prefPane/Contents/MacOS/../Frameworks/libswiftCore.dylib
2017-09-27 23:00:59.922 System Preferences[3047:337095] [NSPrefPaneBundle instantiatePrefPaneObject] (/Users/luckman212/Library/PreferencePanes/SwiftDefaultApps.prefPane): principalClass is nil.
2017-09-27 23:01:00.072 System Preferences[3047:337095] ### AE 1868656752 sender's PID is 3047 (System Preferences)
I haven't upgraded yet and have no way to do it at present, even if I was so-inclined. Haas anybody faced this issue, and/or know the cause for it?