Call function from superclass with different this

Question

I have Owner class, Animal (which might have an owner), Dog (which extends Animal) and a type WithOwner which makes sure that animal has an owner:

type WithOwner<T extends Animal> = T & {
    owner: NonNullable<T["owner"]>;
};
class Owner {
    name: string;
    constructor(name: string) {
        this.name = name;
    }
}
class Animal {
    owner?: Owner;

    ownership(this: WithOwner<Animal>): string {
        return this.owner.name;
    }
}
class Dog extends Animal {
    override ownership(this: WithOwner<Dog>): string {
        return super.ownership() + " owns a dog";
    }
}

However I get an error on super.ownership(): TS2684: The 'this' context of type 'Animal' is not assignable to method's 'this' of type 'WithOwner<Animal>'.. For some reason TS compiler forgets that inside this function animal has an owner.

Any ideas what's going on here and how to fix it? I tried adding if (this.owner) before super but it still didn't help.

Answer 1

Be aware that JavaScript (and typescript) this is implicit supplied to a function, if you want a parameter, don't call it this.

see this link

also this

Answer 2

Figured it out. This works:

class Dog extends Animal {
    override ownership(this: WithOwner<Dog>): string {
        return super.ownership.call(this) + " owns a dog";
    }
}