Is a "wrong" to return anything else besides `this` in a constructor?

Question

Is a "wrong" to return anything else besides this in a constructor?

Take this TypeScript Queue sample:

class Queue {

    private buffer: string;

    constructor(buffer: string = "") {
        this.buffer = buffer;
    }

    push(n: string): Queue {
        return new Queue(this.get() + n);
    }

    get(): string {
        return this.buffer;
    }

    print() {
        console.log(this.buffer);
    }
}
new Queue().add("1").add("2").add("3").print(); // prints 123

Everytime push is called, a new Queue instance is created. And in a child class i would like to prepend a suffix in the queue like this.

class QueuePrefix extends Queue {
    constructor() {
        super();
        return this.push("q:");
    }
}
new QueuePrefix().add("1").add("2").add("3").print(); // prints q:123

However I must return the result from the function push, instead of 'this'.

Is this an acceptable strategy?

Answer 1

I don't think it is wrong per se, as long as the returned object is a subtype of the expected type. But returning anything else would certainly violate the principle of least surprise.

In your particular case I don't see why it is necessary though, you could just initialize the buffer in the constructor.