code: function checkSelector2(i) {
    if (i >= tokensLength) return 0;
  
    const start = i;
    let l;
  
    if (l = checkCombinator(i)) i += l;
    else return 0;
  
    while (i < tokensLength) {
      const spaceBefore = checkSC(i);
      if (l = checkCompoundSelector(i + spaceBefore)) i += spaceBefore + l;
      else break;
  
      const spaceAfter = checkSC(i);
      const comma = checkCombinator(i + spaceAfter);
      if (!spaceAfter && !comma) break;
      if (comma) {
        i += spaceAfter + comma;
      }
    }
  
    tokens[start].selectorEnd = i;
    return i - start;
  }
docs: Checks for a selector that starts with a combinator.