Set operation methods should accept set-like objects via GetSetRecord

[frostney]

Summary

The ES2026 Set operation methods (union, intersection, difference, symmetricDifference, isSubsetOf, isSupersetOf, isDisjointFrom) currently only accept TGocciaSetValue instances as the other argument. Per ES2026 §7.3.45, they should accept any set-like object — an object with size, has(), and keys() — via the GetSetRecord(obj) abstract operation.

Current behavior

const setLike = {
  size: 2,
  has(v) { return v === 1 || v === 2; },
  *keys() { yield 1; yield 2; }
};
new Set([1, 2, 3]).intersection(setLike);
// TypeError: Set.prototype.intersection: argument must be a Set

Expected behavior

new Set([1, 2, 3]).intersection(setLike);
// Set {1, 2}

What needs to happen

1. Implement GetSetRecord(obj) — read .size (coerce to number), .has (require callable), .keys (require callable) from the argument and return a record. Throw TypeError if validation fails.
2. Replace the is TGocciaSetValue argument checks in all 7 Set operation methods with a GetSetRecord call.
3. Update the iteration in each method to use the keys iterator from the record instead of directly accessing FItems.

References

• ES2026 §7.3.45 GetSetRecord(obj)
• ES2026 §24.2.3.12 Set.prototype.union(other) step 4
• Add receiver brand checks to Set/Map prototype methods #421 (comment): Add receiver brand checks to Set/Map prototype methods #421 (comment)