在Xcode11Beta4中将String（format：，args）与SwiftUI一起使用时出错

升级到Xcode 11 Beta 4之后，在String(format: , args)与@Stateproperty一起使用时，我开始看到错误。请参见下面的代码。第二Text行抛出一个错误：

表达式类型“字符串”不明确，没有更多上下文

而Texts 1、3和4可以正常工作。

struct ContentView : View {
    @State var selection = 2

    var body: some View {
        VStack {
            Text("My selection \(selection)") // works
            Text("My selection \(String(format: "%02d", selection))") // error
            Text("My selection \(String(format: "%02d", Int(selection)))") // works
            Text("My selection \(String(format: "%02d", $selection.binding.value))") // works
        }
    }
}

我意识到这是Beta版软件，但很好奇是否有人可以看到此行为的原因，或者仅仅是一个错误。如果无法解释，我将提交雷达报告。

在beta 4中，属性包装器的实现略有变化。在beta 3中，编译器将View重写为：

internal struct ContentView : View {
  @State internal var selection: Int { get nonmutating set }
  internal var $selection: Binding { get }
  @_hasInitialValue private var $$selection: State
  internal var body: some View { get }
  internal init(selection: Int = 2)
  internal init()
  internal typealias Body = some View
}

internal struct ContentView : View {
  @State @_projectedValueProperty($selection) internal var selection: Int { get nonmutating set }
  internal var $selection: Binding { get }
  @_hasInitialValue private var _selection: State
  internal var body: some View { get }
  internal init(selection: Int = 2)
  internal init()
  internal typealias Body = some View
}

Text("My selection \(String(format: "%02d", selection as Int))")