val mapping: CodePointMapping,
  /** Prohibited code points. */
  val prohibitSet: CodePointSet,
  /** RandALCat code points; bidi category is "R" or "AL". */
  val randalcatSet: CodePointSet,
  /** LCat code points; bidi category is "L". */
  val lcatSet: CodePointSet,
) {
  /**
   * Returns [input] in canonical form according to these rules, or null if no such canonical form
   * exists for it.