Nodelist and casting error (also maybe iframe)

[andrewbaxter]

This looks like a bug, but I'm not super familiar with implementation details so I'm making it a discussion for now.

I have

let html_children0 = idoc.query_selector_all("h1,h2,h3,h4,h5,h6,p,img").unwrap();
...
let child = html_children0.item(i).unwrap().dyn_into::<HtmlElement>().unwrap();

This panics when trying to dyn_into with:

called `Result::unwrap()` on an `Err` value: Node { obj: EventTarget { obj: Object { obj: JsValue(HTMLHeadingElement) } } }

I'm not sure what to make of this. is_instance_of returns false for Element HtmlElement and HtmlHeadingElement. I'm pretty sure I've casted nodes to HtmlElement before.

Since I'm half rubber ducking here, it might be significant that this is in an iframe. ...And yeah, doing a search I do see a suggestion about something similar: #1367 (although that sounds like it was eventually something about boxed elements?)