Swift 2, protocol extensions & respondsToSelector

Question

I am not sure, it looks to me that it is some kind of bug or bad implementation with protocol extensions in Swift 2.0.

I have protocolA, protocolB extending protocolA and implementing methods in protocolB extension.

I have conformed an class instance to conform to protocolB, however when inspected by respondsToSelector for protocolA/B methods the results is false.

import Cocoa
import XCPlayground

protocol ProtocolA : NSObjectProtocol {
  func functionA()
}

protocol ProtocolB : ProtocolA {
  func functionB()
}

extension ProtocolB {
   func functionA() {
     print("Passed functionA")
   }

   func functionB() {
     print("Passed functionB")
   }
}

class TestClass : NSObject, ProtocolB {

    override init () {

    }
}

var instance:TestClass = TestClass()
instance.functionA() // Calls code OK..

if instance.respondsToSelector("functionA") {
    print("Responds to functionA") // **False, never passing here**
}

if instance.respondsToSelector("functionB") {
    print("Responds to functionB") // **False, never passing here**
}

Should be reported as a bug?

Answer 1

Interesting. Looks like a bug to me. It does recognize functions on a class, but not on extension. No matter what type Instance has. Moreover without an extension code would not be compilable, since protocol methods are non optional. So really looks like a bug/feature? in responds to selector implementation.