Must call super constructor in derived class before accessing 'this' or returning from derived constructor

[GitaiQAQ]

class Base {}

class Test extends Base {
    constructor() {
        super();
        () => {
            this.aa = 1;
        }
    }
}

$ npx buble test.js -n classes

class Base {}

class A extends Base {
    constructor() {
        var this$1 = this;

        super();
        !function() {
            this$1.aa = 1;
        }
    }
}