In cases like this, we are checking for a labelled by relation between the interactive element and the label and do not find one. There's sort of implicit relation because we are rendering a visible label but do not indicate a relation.

How are we handling, for example, <button>foo</button>?

(In reply to James Teh [:Jamie] from comment #1)

How are we handling, for example, <button>foo</button>?

It has to have a non-empty name.

Okay, so a button doesn't need a visible label? Like <div role="button" aria-label="foo" tabindex="0" onclick=";">...CSS background image...</div>

XUL checkboxes are somewhat different in structure to HTML checkboxes. There is actually a label in the DOM, but we deliberately don't create Accessibles for children of checkboxes, since they're implementation details. I think you might need to special case based on tag here.

I think this would be s2 if it impacted real web content, but it only impacts our browser UI, so setting s3.