// Warning: Layout constraint constraint 'Self' : 'AnyObject' implied here
protocol A: class where Self: NSObject {
    var p: NSObject { get set }
}

class B {
    func doSomethingWith(a: A) {
        a.p = NSObject()
    }
}

protocol A where Self: NSObject {
    var p: NSObject { get set }
}

class B {
    func doSomethingWith(a: A) {
        // Compiler error: Cannot assign to property: 'a' is a 'let' constant
        a.p = NSObject()
    }
}

import UIKit

struct ViewModel {}

// Warning: Layout constraint constraint 'Self' : 'AnyObject' implied here
protocol ViewControllerProtocol: class where Self: UIViewController {
    func setViewModel(_ viewModel: ViewModel)
}

class Presenter {
    func configure(viewController: ViewControllerProtocol) {
        viewController.setViewModel(ViewModel())
    }
}

class ViewController: UIViewController {
    var viewModel: ViewModel?
}

extension ViewController: ViewControllerProtocol {
    func setViewModel(_ viewModel: ViewModel) {
        self.viewModel = viewModel
    }
}

let viewController = ViewController()
let presenter = Presenter()
presenter.configure(viewController: viewController)