     return 17
   }
 }
+extension X: P {
+  @objc func e() { print("X.e()") }
+}
 
 class Y { 
   init() {}
   @objc class func g() { print("Y.g()") }
 }
+extension Y: P {}
 
 class Z {
    init() {}

  if of != nil {
    of!()
  } else {
    print("Object does not respond to the selector \"f\".\n", terminator: "")
  }
}


// REQUIRES: objc_interop

import Foundation

@objc protocol P {
  @objc optional func e()
}

class X {
  init() {}
