a custom class extends to Object, invoke a member function will produce an error!!! #14869

class Base extends Object /* or extends Array */ {
}

class Greeter extends Base {
    greeting: string;
    constructor(message: string) {
        super();
        this.greeting = message;

        this.greet(); // <-- error here
    }
    greet() {
        return "Hello, " + this.greeting;
    }
}

let greeter = new Greeter("world");

let button = document.createElement('button');
button.textContent = "Say Hello";
button.onclick = function() {
    alert(greeter.greet());
}

document.body.appendChild(button);