上下文类型＆＃39; MGTransitioningOptions＆＃39;不能与数组字面意思一起使用？

Question

有一次我在Swift 3之前猜测下面的代码行用于编译，但现在却没有：

var directions: MGTransitioningOptions = [.DirectionUp]

它会出现以下错误：＆＃34;上下文类型＆＃39; MGTransitioningOptions＆＃39;不能与数组文字＆＃34;

一起使用

以下是创建MGTransitioningOptions的结构的代码：

struct MGTransitioningOptions: OptionSet {
    internal let rawValue: Int
    init(rawValue: Int) {self.rawValue = rawValue}
    static let DirectionUp = MGTransitioningOptions(rawValue: 1<<1)
    static let DirectionDown = MGTransitioningOptions(rawValue: 1<<2)
    static let DirectionLeft = MGTransitioningOptions(rawValue: 1<<3)
    static let DirectionRight = MGTransitioningOptions(rawValue: 1<<4)
    static let AlphaChange = MGTransitioningOptions(rawValue: 1<<5)
    static let BlurBackground = MGTransitioningOptions(rawValue: 1<<5)
    static let Dissolve = MGTransitioningOptions(rawValue: 1<<6)
    static let Interactive = MGTransitioningOptions(rawValue: 1<<7)
}