same method
Will return true
if the sets internals are the same instances
(comparing by identity). This will be fast even for very large sets,
since it doesn't compare each item.
May can also return true
under some other situations where it's very
cheap to determine that the sets are equal even if the sets internals
are NOT the same.
Note: This is not the same as identical(set1, set2)
since it doesn't
compare the sets themselves, but their internal state. Comparing the
internal state is better, because it will return true more often.
Implementation
@override
bool same(ISet<T>? other) =>
(other != null) &&
(other is ISetEmpty || (other is ISetConst && (other as ISetConst)._set.isEmpty)) &&
(config == other.config);