序列'需要类型'ZBarSymbolSet.Element'（又名'ZBarSymbol'）和'Any'是等价的

Question

此代码适用于Swift 3，但因Swift 4错误而失败：

  

'Sequence'需要类型'ZBarSymbolSet.Element'（又名'ZBarSymbol'）和'Any'是等价的

extension ZBarSymbolSet: Sequence
{
    public typealias Element  = ZBarSymbol
    public typealias Iterator = NSFastEnumerationIterator

    public func makeIterator() -> NSFastEnumerationIterator
    {
        return NSFastEnumerationIterator(self)
    }
}

...

if (self.ZBarReader == nil) {
    self.ZBarReader = ZBarReaderViewController()
}
self.ZBarReader?.readerDelegate = self
self.ZBarReader?.scanner.setSymbology(ZBAR_UPCA, config: ZBAR_CFG_ENABLE, to: 1)
self.ZBarReader?.readerView.zoom = 1.0
self.ZBarReader?.isModalInPopover = false
self.ZBarReader?.showsZBarControls = false
navigationController?.pushViewController(self.ZBarReader!, animated:true)

...

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any])
{
    guard let symbols = info[ZBarReaderControllerResults] as? ZBarSymbolSet else { return }

    for symbol in symbols
    {
         if let symbol = symbol as? ZBarSymbol, let data = symbol.data
         {
            print(data)
         }
     }
}

我在这里做错了什么？