Multiple kings per color (was_into_check and more affected) (#1179)

* fixed multiple kings for was_into_check

* fixed king() behavior on multiple kings

minus prev commit

* add test cases (very little)

* using the precomputed king mask

* removed testcase of was_into_check() on multiple kings...

... because it would cause the function to return False (because king() didn't detect any king because of decision)

Author: winapiadmin

chess/__init__.py

@@ -916,7 +916,7 @@ def king(self, color: Color) -> Optional[Square]:
         considered.
         """
         king_mask = self.occupied_co[color] & self.kings & ~self.promoted
-        return msb(king_mask) if king_mask else None
+        return msb(king_mask) if king_mask and popcount(king_mask) == 1 else None
 
     def attacks_mask(self, square: Square) -> Bitboard:
         bb_square = BB_SQUARES[square]

test.py

@@ -1720,6 +1720,10 @@ def test_impossible_check_due_to_en_passant(self):
         self.assertFalse(board.has_legal_en_passant())
         self.assertEqual(len(list(board.legal_moves)), 2)
 
+    def test_multiple_kings(self):
+        board = chess.Board("KKKK1kkk/8/8/8/8/8/8/8 w - - 0 1")
+        self.assertEqual(board.king(chess.WHITE), None)
+
 
 class LegalMoveGeneratorTestCase(unittest.TestCase):