https://twitter.com/krzyzanowskim/status/577846666587430915

swift_failable_initiaizer_bug

import Foundation

public class Foo {
    private var key:NSData
    private var goo:NSData?
    
    public init(key: NSData) {
        self.key = key
        self.goo = nil
    }
    
    convenience init?(keyy:String, gooo:String) {
        let kkey = keyy.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)
        let ggoo = gooo.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)

        if  let kkey = kkey, let ggoo = ggoo
        {
            self.init(key:kkey)
        } else {
            return nil
        }
    }
}

rdar://problem/20193929