This is an archived snapshot of W3C's public bugzilla bug tracker, decommissioned in April 2019. Please see the home page for more details.
In http://w3c.github.io/aria-in-html/#what-does-adding-a-role-do-to-the-native-semantics, under the heading "What adding a role does not do", it is reported that a button with a role of "heading" and an aria-level of "1" will become "(none) heading" in the accessibility tree. No indication that the level will/should be provided (eg. "level 1" or "first level") is given. It is inadequate as well that the alt text for the image of this accessibility tree snippet just reads "a heading".