Another.swift

    public func tr_pushViewController<T where T: TRTransition, T.Content == UIViewController>(viewController: T, method: TRPushMethod, statusBarStyle: TRStatusBarStyle = .Default, completion: (() -> Void)? = nil) {
        guard let vc = viewController as? T.Content else {
            fatalError()
        }
        let transitionDelegate = TRNavgationTransitionDelegate(method: method, status: .Push, gestureFor: vc)
        transitionDelegate.completion = completion
        viewController.tr_transition = transitionDelegate
        delegate = transitionDelegate
        transitionDelegate.previousStatusBarStyle = TRStatusBarStyle.CurrentlyTRStatusBarStyle()
        transitionDelegate.currentStatusBarStyle = statusBarStyle
        pushViewController(vc, animated: true)
    }

TRTransition.swift

protocol TRTransition {
    typealias Content = Self
}

extension UIViewController: TRTransition {

}

extension Int: TRTransition {
    
}

func miao<T where T: TRTransition, T.Content == UIViewController>(param: T) {
    let p = param as! UIViewController
    print(p.dynamicType)
}

miao(UIViewController()) // This is OK
miao(UITableViewController())  // This is also OK
miao(1) // Will not compile