private BoxUniquenessRule(BoxUniquenessRule existing, IReadOnlyPuzzle?puzzle)
: base(existing)
{
_boxSize = existing._boxSize;
_puzzle = puzzle;
}
private BoxUniquenessRule(BoxUniquenessRule existing, IReadOnlyBoxPuzzle puzzle)
{
_puzzle = puzzle;
_unsetBoxValues = existing._unsetBoxValues.AsSpan().ToArray();
_skipMatchingRowAndCol = existing._skipMatchingRowAndCol;
}