typings: oncancel? should be EventHandler<Event,T> instead of EventHandler<T>

[pschyska]

Describe the bug
I think the type of oncancel is incorrect. For example on a HTMLDialogElement this resolves to EventHandler<HTMLElement,HTMLElement>. I think oncancel (and probably every other handler referencing EventHandler<T>) should be typed:
oncancel?: EventHandler<Event,T>;

To Reproduce

<script lang="ts">
function cancel(ev: Event)  {
    ev.stopImmediatePropagation();
    ev.preventDefault()
}
</script>

<main>
    <dialog on:cancel="{cancel}">
    </dialog>
</main>

This type errors like this:

Type '(ev: Event) => void' is not assignable to type 'EventHandler<HTMLElement, HTMLElement>'.
  Types of parameters 'ev' and 'event' are incompatible.
    Type 'HTMLElement & { currentTarget: EventTarget & HTMLElement; }' is missing the following properties from type 'Event': bubbles, cancelBubble, cancelable, composed, and 17 more.ts(2322)

According to MDN, this should be a legal handler.

Expected behavior
In this concrete example, I think the type should be EventHandler<Event, HTMLDialogElement>. Or EventHandler<Event, HTMLElement> if there is a reason to not type it as HTMLDialogElement that escapes me right now. (iow: why is dialog not a HTMLProps<HTMLDialogElement>)

[pschyska]

@jasonlyu123 What do you think about dialog being typed as HTMLProps<HTMLDialogElement>, while we are at it :-)

[jasonlyu123]

It looks like there's plenty of them is typed as HTMLProps<HTMLElement>. I think we can change it to

type HTMLElementPropMap = {
    [k in keyof HTMLElementTagNameMap]: HTMLProps<HTMLElementTagNameMap[k]>
}
interface IntrinsicElements extends HTMLElementPropMap { }

and remove the overlaps.

[dummdidumm]

Sounds good, we just need to look very closely to not throw out tags that are present now by accident.

[dummdidumm]

Closing as the original issue has been resolved. For the other things, feel free to open a separate issue.