Faulty @DestroyAware

export function DestroyAware(destroyHookName: string = "ngOnDestroy"): Function {
    return (target: Object, key: string): void => {
        let originalDestroyHook: Function;
        if (destroyHookName in target && target[destroyHookName] instanceof Function) {
            originalDestroyHook = target[destroyHookName];
        }

        Object.defineProperty(target, destroyHookName, {
            value: function value(...args: any[]) {
                if (originalDestroyHook instanceof Function) {
                    originalDestroyHook.apply(this, args);
                }
                this[key].next(true);
                this[key].complete();
            }
        });
    };
}