fn matches_complex_selector_internal<E>(
    selector_iter: SelectorIter<'_, E::Impl>,
    element: &E,
    context: &mut MatchingContext<'_, E::Impl>,
    rightmost: SubjectOrPseudoElement,
    first_subject_compound: SubjectOrPseudoElement
) -> SelectorMatchingResultwhere
    E: Element,