src/language-css/parser-postcss.js/parseWithParser
function parseWithParser(parse, text, options) {
  const parsed = parseFrontMatter(text);
  const { frontMatter } = parsed;
  text = parsed.content;

  let result;

  try {
    result = parse(text);
  } catch (e) {
    if (typeof e.line !== "number") {
      throw e;
    }
    throw createError("(postcss) " + e.name + " " + e.reason, { start: e });
  }

  result = parseNestedCSS(addTypePrefix(result, "css-"), options);

  calculateLoc(result, text);

  if (frontMatter) {
    result.nodes.unshift(frontMatter);
  }

  return result;
}