Xcode part15

>>428
@propertyWrapper
struct Makeshift<T> {
private var value: T
private var setFlag = false
init(wrappedValue v: T) {
value = v
}

var wrappedValue: T {
get { value }
set {
if setFlag { print("already set") }
value = newValue
setFlag = true
}
}
}
struct A {
@Makeshift(wrappedValue: 1)
var counter: Int
}

これなら、動いた。@Swift5.1