`
(?:${escapeChar}[\\S\\s]|(?:(?!${
  // Using `XRegExp.union` safely rewrites backreferences in `left` and `right`.
  // Intentionally not passing `basicFlags` to `XRegExp.union` since any syntax
  // transformation resulting from those flags was already applied to `left` and
  // `right` when they were passed through the XRegExp constructor above.
  XRegExp.union([left, right], "", { conjunction: "or" }).source
})[^${escapeChar}])+)+
`;

`a${/* b */ c /* d */}e${
  // f
  g
  // h
}`;