Perhaps worth noting, here is the output of otool -L:
/System/Library/Frameworks/Foundation.framework/Versions/C/Foundation (compatibility version 300.0.0, current version 1555.10.0)
/System/Library/Frameworks/Cocoa.framework/Versions/A/Cocoa (compatibility version 1.0.0, current version 23.0.0)
@rpath/Alamofire.framework/Versions/A/Alamofire (compatibility version 0.0.0, current version 0.0.0)
@rpath/KeychainAccess.framework/Versions/A/KeychainAccess (compatibility version 0.0.0, current version 0.0.0)
/usr/lib/libobjc.A.dylib (compatibility version 1.0.0, current version 228.0.0)
/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1252.200.5)
/System/Library/Frameworks/AppKit.framework/Versions/C/AppKit (compatibility version 45.0.0, current version 1670.0.0)
@rpath/libswiftAppKit.dylib (compatibility version 1.0.0, current version 1000.11.37)
@rpath/libswiftCore.dylib (compatibility version 1.0.0, current version 1000.11.37)
@rpath/libswiftCoreData.dylib (compatibility version 1.0.0, current version 1000.11.37)
@rpath/libswiftCoreFoundation.dylib (compatibility version 1.0.0, current version 1000.11.37)
@rpath/libswiftCoreGraphics.dylib (compatibility version 1.0.0, current version 1000.11.37)
@rpath/libswiftCoreImage.dylib (compatibility version 1.0.0, current version 1000.11.37)
@rpath/libswiftDarwin.dylib (compatibility version 1.0.0, current version 1000.11.37)
@rpath/libswiftDispatch.dylib (compatibility version 1.0.0, current version 1000.11.37)
@rpath/libswiftFoundation.dylib (compatibility version 1.0.0, current version 1000.11.37)
@rpath/libswiftIOKit.dylib (compatibility version 1.0.0, current version 1000.11.37)
@rpath/libswiftMetal.dylib (compatibility version 1.0.0, current version 1000.11.37)
@rpath/libswiftObjectiveC.dylib (compatibility version 1.0.0, current version 1000.11.37)
@rpath/libswiftQuartzCore.dylib (compatibility version 1.0.0, current version 1000.11.37)
@rpath/libswiftXPC.dylib (compatibility version 1.0.0, current version 1000.11.37)
What I'm not understanding is how a system swift library can have a missing symbol. I've tried embedding swift standard libraries and received the same error. Can you not have a Swift 4.2 app on macOS 10.12?
