Wow. All these years I would've sworn that there is absolutely no difference between applying private to the extension versus to each declaration individually, but lo and behold, it turns out I just never checked...
The following doesn't compile!
func checkIsEven (_ int: Int) -> Bool {
int.isEven // Error: 'isEven' is inaccessible due to 'private' protection level
}
extension Int {
private var isEven: Bool {
self % 2 == 0
}
}
Thank you for the insight 