@State of optional: type spelling Optional<Int> is not the same as Int?

Using Swift
5

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struct ContentView: View {
    @State var a: Int?
    
    init() {
        a = 5
    }
    
    var body: some View {
        VStack {
            Text("\(a ?? -1)") // Show -1
        }
    }
}

struct ContentView: View {
    @State var a: Int?
    @State var b: Optional<Int>
    
    init() {
        a = 5
        b = 5
    }
    
    var body: some View {
        VStack {
            Text("\(a ?? -1)") // Show 5 (unexpected, why?)
            Text("\(b ?? -1)") // Show 5 (expected)
        }
    }
}

If we use debugger and disassemble it, we'll find that variable _a got init twice.

1.  `@State var a: Int?` // _a = State<Int?>(wrappedValue: nil)
2.  `a = 5` in init funcation // _a = State<Int?>(wrappedValue: 5) // Unexpected
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