duplicates:

• SR-9479 Subclasses of generic classes don't remember @objc names for optional protocol methods

Issue Description:

Consider:

import Foundation

@objc
protocol Protocol {
    @objc
    optional func one() -> Int
    @objc
    optional func two() -> Int
}

public class Outer<M> {
    public class Inner: Protocol {
        public func two() -> Int {
            return 0
        }
    }
    public class Extended: Inner {
        public func one() -> Int {
            return 1
        }
        public override func two() -> Int {
            return 1
        }
    }
}

let object : Protocol = Outer<String>.Extended()
print( "one: ", object.one?() ) // one:  nil
print( "two: ", object.two?() ) // two:  Optional(1)

The fact that the Outer type is generic causes the Extended object's one function to become inaccessible. The object's two function remains available only because it overrides a function declared at the level where the Protocol is declared. If the Protocol declaration moves from the Inner to the Extended level, the one function will become available again.

Somehow, this peculiar behaviour is triggered explicitly by the fact that Outer is a generic type. Removing the generic qualifier from Outer restores sanity to the situation.