Swift class Equatable need check parent class

class_Equatable.swift

class A: Equatable {
    let name: String
    
    init(name: String) {
        self.name = name
    }
    
    static func ==(lhs: A, rhs: A) -> Bool {
        return lhs.name == rhs.name
    }
}

class B: A {
    let identifier: String
    
    init(name: String, identifier: String) {
        self.identifier = identifier
        super.init(name: name)
    }
    
    static func ==(lhs: B, rhs: B) -> Bool {
        (lhs as A) == (rhs as A) && // !!! this is important
        lhs.identifier == rhs.identifier
    }
}

let b1 = B(name: "one", identifier: "three")
let b2 = B(name: "ones", identifier: "three")
print(b1 == b2)