Playground execution failed:
error: Empty.playground:6:8: error: module compiled with Swift 4.1.2 cannot be imported by the Swift 4.2 compiler: /Users/ellen/Library/Developer/Xcode/DerivedData/Empty-aiojmrqftycfwvbtpmkzvlsjvgjl/Build/Products/Debug-iphonesimulator/Result.framework/Modules/Result.swiftmodule/x86_64.swiftmodule
import Result
^