Function parse_negation 

fn parse_negation<'i, P, Impl>(
    parser: &P,
    input: &mut Parser<'i>,
    state: SelectorParsingState,
) -> Result<Component<Impl>, ParseError<P::Error>>
where
    P: Parser<'i, Impl = Impl>,
    Impl: SelectorImpl,

Level 3: Parse one simple_selector. (Though we might insert a second implied “|*” type selector.)