Doing bad things with delegation

Playground.swift

import UIKit
import CoreLocation
import XCPlayground

XCPlayground.XCPlaygroundPage.currentPage.needsIndefiniteExecution = true

class LocationDelegate: NSObject, CLLocationManagerDelegate {
    override var description: String {
        get {
            return "LocationDelegate"
        }
    }
}

extension CLLocationManager {
    var myDelegate: LocationDelegate {
        get {
            guard self.delegate == nil else {
                fatalError("You're shit outta luck.")
            }
            
            self.delegate = LocationDelegate()
            // 👇 Calling this fails because self.delegate is nil.
            return self.delegate as! LocationDelegate
        }
    }
}

var locationManager = CLLocationManager()
print(locationManager.myDelegate.description)

Maybe I'm missing something but why do any of this? What's wrong with:

let locationDelegate = LocationDelegate()
let locationManager = CLLocationManager()
locationManager.delegate = locationDelegate