swift4 - Swift 4 KVC - Cast to unrelated type always fail -


i not able conditional cast keypath related object keypath superclass. have easy setup 

class foo {     let name: string     init(name: string) {         self.name = name     } } class bar: foo {}  let keypath = \bar.name if let keypath = keypath as? keypath<foo, string> {     print(keypath) }

it's giving me warning print method never executed because

cast 'keypath<bar, string>' unrelated type 'keypath<foo, string>' fails

generally speaking want able operate anyobject inside keypath behaviour preventing me doing that. can explain how downcasting works keypath , perhaps offer way around?


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