```
import Foundation

struct Slot: Equatable {
    let time: Date?
}

class Handler {
    var slot: Slot? {
        didSet {
            guard
                slot != oldValue // breakpoint here
            else {
                return
            }
        }
    }
    
    init() {
        self.slot = .init(time: Date()) // slot is set already in init, so oldValue cannot be nil when breakpoint is triggered
    }
}

let handler = Handler()
handler.slot = .init(time: .distantFuture)
handler.slot = .init(time: .distantPast)
```