Function classes_in_css 

pub fn classes_in_css(css: &str) -> BTreeSet<String>

The class names a stylesheet’s selectors match.

Public because the check this exists for reads an app’s stylesheet too, and comparing what makeover defines against what the app defines is only meaningful if both sides were read the same way.

Selector text only. A declaration value can hold a dot (0.5rem, transition: .2s) and none of those are classes, so the scan tracks whether it is inside a declaration block and ignores what it finds there. An at-rule block (@layer, @media, @supports) contains rules rather than declarations, which is why a depth counter alone is not enough: the stack records what kind of block each brace opened.