Node.parentElement should be Element, not HTMLElement

[cmlenz]

The declaration of the parentElement property on the Node interface in lib.d.ts states that it is of type HTMLElement while it should be Element (see the spec).

[zhengbli]

This is arguable, because there was complainant before saying that it was too cumbersome to always cast the type Element to HTMLElement when in most common cases the actual type is HTMLElement, even though the spec says it should be Element.

For example, the return type of getElementById is defined as Element, however we made it HTMLElement to avoid too much casting. If the type is some other Element, you can just cast it to Element first and then cast it again to the final type. I think in most cases the parentElement is HTMLElement too, therefore it might be better just leave it the way it is.

[leonyu]

I just encountered this bug. The issue occurred with SVG on the page.

Maybe this can be solved with generics? Though the syntax would be ridiculous. (e.g. Node<Element<HTMLElement>>>