message: OrderedSet intersection tweak
diff: @@ -170,6 +170,7 @@ function intersectSI(a: S, b: I) {
  const start = I.start(r), end = I.end(r);
  const resultSize = end - start;
  if (!resultSize) return Empty;
  + if (resultSize === a.length) return a;
  const indices = new Int32Array(resultSize);
  let offset = 0;
  