Allow this as return type from static methods

[iby]

TypeScript allows to return this from instance methods, which is to say the least, is great. It would be even better if it allowed doing the same with static methods. The rationale is consistency and feature.

Line public static construct():this below will report error TS2526: A 'this' type is available only in a non-static member of a class or interface., the line below uses this inside static method to create a new instance of the class, the line below that also uses this to return static property. The error message is misleading, this can be and should be used inside static methods whenever appropriate.

class Foo {
    public static x:any;
    protected y:any;
    public static construct():this {
        return new this();
    }
    public static getX():any {
        return this.x;
    }
    public getY():any{
        return this.y;
    }
    public setY(value:any):this{
        this.y = value;
        return this;
    }
}

I'd like to inherit Foo and use construct on child classes, the only way I can do this by specifying Foo as return type, however, this will require to cast the result to Bar and Baz whenever called from those classes – inconvenient and inconsistent with instance method behaviour.

This seems to be common sense, since this already done for instance methods, shouldn't be much pain doing this for static methods either? What are your thoughts?

[mhegazy]

Duplicate of #5863