// Xcode 12 beta 1
// Deployment target: iOS 14
// -------------------------------------
@available(iOS 15.0, *)
protocol Foo {}

class A: Foo {} // This doesn't trigger an error

class B {}
extension B: Foo {} // No error

class C {
    let foo: Foo! // 'Foo' is only available in iOS 15.0 or newer
    init() {
        fatalError()
    }
}

let a1 = A() // No error

let a2: Foo = A() // ''Foo' is only available in iOS 15.0 or newer'

func foo1<T: Foo>() -> T { fatalError() } // ''Foo' is only available in iOS 15.0 or newer'

func foo2(arg: Foo) { fatalError() } // ''Foo' is only available in iOS 15.0 or newer'

@available(iOS 15, *)
protocol P {
  var foo: Int { get }
}

protocol Q: P {}
struct S: Q { let foo = 0 }
class C<T: Q> {}

let s = C<S>()