message: added missing return types for set utils
diff: @@ -15,14 +15,14 @@ export function isSuperset<T>(setA: Set<T>, setB: Set<T>) {
  }
  /** Create set containing elements of both set a and set b. */
  -export function union<T>(setA: Set<T>, setB: Set<T>) {
  +export function union<T>(setA: Set<T>, setB: Set<T>): Set<T> {
  const union = new Set(setA);
  for (const elem of Array.from(setB)) union.add(elem);
  return union;
  }
  /** Create set containing elements of set a that are also in set b. */
  -export function intersection<T>(setA: Set<T>, setB: Set<T>) {
  +export function intersection<T>(setA: Set<T>, setB: Set<T>): Set<T> {
  const intersection = new Set();
  for (const elem of Array.from(setB)) {
  if (setA.has(elem)) intersection.add(elem);
  @@ -31,7 +31,7 @@ export function intersection<T>(setA: Set<T>, setB: Set<T>) {
  }
  /** Create set containing elements of set a that are not in set b. */
  -export function difference<T>(setA: Set<T>, setB: Set<T>) {
  +export function difference<T>(setA: Set<T>, setB: Set<T>): Set<T> {
  const difference = new Set(setA);
  for (const elem of Array.from(setB)) difference.delete(elem);
  return difference;
  