Function peek_ranged_feature_name 

pub fn peek_ranged_feature_name<'a, I>(p: &Parser<'a, I>) -> Cursor
where
    I: Iterator<Item = Cursor> + Clone,

Looks ahead from a ranged feature’s opening ( to its <feature-name>, skipping any leading <value>, including nested blocks such as the calc() in (calc(1px + 2px) < width). Returns the cursor of the first top-level ident, or of the closing ) or EOF when there is none. Lookahead stops at the u8::MAXth token, returning that cursor.