:has() use cases

[ffoodd]

Probably tons of new tests to find, using :has(). A few resources:

• "The CSS :has() selector is way more than a “Parent Selector”" by Bramus.
• "Meet :has(), A Native CSS Parent Selector (And More)" by Adrian Bece on Smashing Magazine.
• "CSS :has() a parent selector now" by Matthias Ott.

Checking for some patterns based on nesting elements, or some ARIA design patterns, should become possible!

Also it'd allow to drop the current %a11y-reset placeholder.

[ffoodd]

@KittyGiraudel opens a new door checking details:not(:has(> summary)):not([tabindex^="-"]) in focusable-selectors. Checking for required children (apart from their focusability) is a new step forward validating HTML through CSS.

Need time to play with this :)