How to declare a built-in class which also should be a table?

[dmi7ry]

Hi. There is a built-in class which available in scripts as a table.
Currently I delcared it like this:

declare class Element
    alpha: number
    angularVelocity: Vector3
    attached: boolean
    ...
    __call: (elementType: string, elementID: string?) -> Element
    ...
    function addDataSubscriber(self, element: Element, key: string, player: Player): boolean
    function attach(self, theAttachToElement: Element, xPosOffset: number?, yPosOffset: number?, zPosOffset: number?, xRotOffset: number?, yRotOffset: number?, zRotOffset: number?): boolean
    function clearVisibility(self): boolean
    ...
end
declare Element: Element

But if I do something like this

function Element.get(id: number)
    ...

it shows an error:

TypeError: Cannot add method to non-table type 'Element' Luau(1005)

How should this be done right?

[vegorov-rbx]

Table types are declared using

declare Element: {
    a: number,
    ...
}

[dmi7ry]

The class Element is parent class for many other, like declare calss Vehicle extends Element. Is it possible to extend a class from such table?