Open Radar

 
In the following code, adding the “NSObject” type constraint causes all “is T” checks to return true. This appears to be true of any ObjC type constraint. A type constraint of AnyObject does not cause this problem.

import UIKit

let vc1 = UIViewController()

func istypeGood<T>(check: AnyObject, kindOf: T.Type) -> (Bool) {
    return check is T
}

func istypeBad<T: NSObject>(check: AnyObject, kindOf: T.Type) -> (Bool) {
    return check is T
}


istypeGood(vc1, kindOf: UIView.self) // false, correct
istypeGood(vc1, kindOf: UIViewController.self)  // true, correct

istypeBad(vc1, kindOf: UIView.self) // true, incorrect   <======
istypeBad(vc1, kindOf: UIViewController.self)  // true, correct