protocol Returnable {
    associatedtype T
    var v: T { get set }

    func check() -> T
}

class GenericClass<U>: Returnable {
    typealias T = U

    var v: U

    init(_ v: U) {
        self.v = v
    }

    func check() -> U {
        return v
    }

}

var g = GenericClass<String>("TILT")
g.check()