protocol A {}
protocol P {
    associatedtype T
    var value: T { get }
    func tIsA() -> Bool
}


extension P {
    func tIsA() -> Bool {
        false
    }
}


extension P where T: A {
    func tIsA() -> Bool {
        true
    }
}


struct X: A {}
struct AnyP<T>: P {
    var value: T
}


func check(x: X) {
    print(AnyP(value: x).tIsA())
}


func check2<X2>(x: X2) {
    print(AnyP(value: x).tIsA())
}


check(x: X()) // true
check2(x: X()) // false