Open Radar

 
Summary:
If a method is defined to use a generic type that is constrained to be a subclass of a specified class, and to also implement a specified protocol, the compiler crashes.

Steps to Reproduce:
Paste this code into a playground:

protocol CanBark {
    func bark() -> String
}

class Animal {
    func animalType() -> String {
        return "Animal"
    }
}

class Dog: Animal, CanBark {
    override func animalType() -> String {
        return "Dog"
    }

    func bark() -> String {
        return "Woof"
    }
}

func makeAnimalBark<T where T: CanBark, T: Animal>(barkingAnimal: T) {
    let animalType = barkingAnimal.animalType()
    let bark = barkingAnimal.bark()
    println("\(animalType) says \"\(bark)\"")
}

let dog = Dog()
makeAnimalBark(dog)              // Dog says "Woof"


Expected Results:
Should print 'Dog says "Woof"'

Actual Results:
Compiler crashes.



Version:
Xcode 6 beta 5 (6A279r)

Notes:
A workaround is to explicitly cast the argument to the protocol type before calling the function defined by the protocol, like this:

func makeAnimalBark<T where T: CanBark, T: Animal>(barkingAnimal: T) {
    let animalType = barkingAnimal.animalType()
    let canBark = barkingAnimal as CanBark
    let bark = canBark.bark()
    println("\(animalType) says \"\(bark)\"")
}

Configuration:
OS X 10.9.4

Attachments:
'com.apple.dt.Xcode.Playground_2014-08-06-072356_pluto.crash' was successfully uploaded.

----

Apple Developer Relations 29-Sep-2014 06:54 PM

We believe this issue has been addressed in the latest Xcode 6.1 beta.  

This pre-release version of the Xcode 6.1 developer tools is required when developing for OS X Yosemite, and includes the Swift programming language. Xcode 6.1 beta runs on OS X Mavericks and OS X Yosemite Developer Preview.

Xcode 6.1 beta - Build 6A1042b