A syntax for returning "this" for method call chaining would be great

[philthy256]

When you've got a bit of inheritance going on, there can be limits to what you can do with method chaining. Say you've got these two classes:

class Animal {
    public sleep() : Animal {
        return this;
    }
}

class Elephant extends Animal {
    public squirtWithTrunk(): Elephant {
        return this;
    }
}

Given an instance of Elephant, you could do this:
myElephant.squirtWithTrunk().sleep()

but you couldn't do this:
myElephant.sleep().squirtWithTrunk()

Because Animal doen't have a "squirtWithTrunk" method.

Seems fair enough, but given how much code space method chaining can save, and how much that can matter in JavaScript, it's a shame. And obviously in raw JavaScript this sort of thing just works.

If the following syntax were allowed, and "this" could be passed through a method chain without its type being narrowed to ancestor types, I think that might be quite nice:

class Animal {
    public sleep() : this {
    }
}

class Elephant extends Animal {
    public squirtWithTrunk(): this {
    }
}

I don't know how feasible that would be from a compiler point of view, but as a user of the language I'd find it very useful. In the last code snippet I imagine that the return statement would be disallowed, and that the returned value would always be the current object.

[sandersn]

TypeScript already works this way. You do have to return this at the end of each method though.

[sandersn]

See #4910

[philthy256]

@sandersn That's awesome, thank you!

The following works a treat - great stuff:

class Animal {
public sleep() {
return this;
}
}

class Elephant extends Animal {
public squirtWithTrunk() {
return this;
}
}