Swift 4 extension default implementation vs. inheritance

swift-extension-default-implementation.swift

import Cocoa

// see https://team.goodeggs.com/overriding-swift-protocol-extension-default-implementations-d005a4428bda

protocol ToString {
    func toString() -> String
}

extension ToString {

    func toString() -> String {
        return "extension default implementation"
    }

}

class Person: ToString {

    func print() {
        Swift.print(toString())
    }

}

class Student: Person {

    // override extension default implementation
    func toString() -> String {
        return "Student"
    }

}

let person = Person()
person.print() // extension default implementation

let student = Student()
student.print() // extension default implementation