Method parse

crates/css_ast/src/selector/nth.rs:23–124

(p: &mut Parser<'a, I>)

impl<'a> Parse<'a> for Nth {
	fn parse<I>(p: &mut Parser<'a, I>) -> ParserResult<Self>
	where
		I: Iterator<Item = Cursor> + Clone,
	{
		if p.peek::<CSSInt>() {
			return Ok(Self::Integer(p.parse::<CSSInt>()?));
		} else if p.peek::<T![Ident]>() {
			let peek_cursor = p.peek_n(1);
			let atom = p.to_atom::<CssAtomSet>(peek_cursor);
			if atom == CssAtomSet::Odd {
				let ident = p.parse::<T![Ident]>()?;
				return Ok(Self::Odd(ident));
			} else if atom == CssAtomSet::Even {
				let ident = p.parse::<T![Ident]>()?;
				return Ok(Self::Even(ident));
			}
		}

		let mut c = p.next();

		let a;
		let mut b_sign = 0;
		let mut cursors = [c, Cursor::EMPTY, Cursor::EMPTY, Cursor::EMPTY];

		if c == '+' {
			let skip = p.set_skip(KindSet::NONE);
			c = p.next();
			p.set_skip(skip);
			debug_assert!(cursors[1] == Cursor::EMPTY);
			cursors[1] = c;
		}
		if !matches!(c.token().kind(), Kind::Number | Kind::Dimension | Kind::Ident) {
			Err(Diagnostic::new(c, Diagnostic::unexpected))?
		}
		if c.token().is_float() {
			Err(Diagnostic::new(c, Diagnostic::expected_int))?
		}

		if p.equals_atom(c, &CssAtomSet::_NDash) {
			b_sign = -1;
			a = if c.token().is_int() { c.token().value() as i32 } else { 1 };
		} else {
			let source_cursor = p.to_source_cursor(c);
			let anb = source_cursor.parse(p.bump());
			let mut chars = anb.chars();
			let mut char = chars.next();
			a = if c.token().is_int() {
				c.token().value() as i32
			} else if char == Some('-') {
				char = chars.next();
				-1
			} else {
				1
			};
			if !matches!(char, Some('n') | Some('N')) {
				Err(Diagnostic::new(c, Diagnostic::unexpected))?
			}
			if let Ok(b) = chars.as_str().parse::<i32>() {