rdar://22678998 Swift 2.0 GM: Selector matching error when implementing an @objc protocol's function that throws.

objc-protocol-throws.swift

@objc protocol P {
    func execute() throws
    
    // Solution: https://twitter.com/jckarter/status/643189428781846528
    // @objc(executeAndReturnError:) func execute() throws
}

class A : P {
    // Error: Type 'A' foes not conform to protocol 'P'
    // Detail 1: Protocol requires function 'execute()' with type '() throws -> ()'
    // Detail 2: Objective-C method 'executeAndReturnError:' provided by method 'execute()' does not match the requirement's selector ('execute')
    @objc func execute() throws {
        try x()
    }
}