function readComment(source, start, line, col, prev) {
  var body = source.body;
  var code = void 0;
  var position = start;

  do {
    code = charCodeAt.call(body, ++position);
  } while (code !== null && (
  // SourceCharacter but not LineTerminator
  code > 0x001F || code === 0x0009));

  return new Tok(COMMENT, start, position, line, col, prev, slice.call(body, start + 1, position));
}
Reads a comment token from the source file.

#[\u0009\u0020-\uFFFF]*