chore: make the return of winner -> Option<Option<Color>>

games/src/ataxx/position.rs

@@ -112,7 +112,7 @@ impl PositionType for Position {
 			white == BitBoard::EMPTY || black == BitBoard::EMPTY // No pieces left
     }
 
-    fn winner(&self) -> Option<Color> {
+    fn winner(&self) -> Option<Option<Color>> {
         if self.half_move_clock >= 100 {
             // Draw by 50 move rule.
             return None;
@@ -124,10 +124,10 @@ impl PositionType for Position {
 
         if black == BitBoard::EMPTY {
             // Black lost all its pieces, White won.
-            return Some(Color::White);
+            return Some(Some(Color::White));
         } else if white == BitBoard::EMPTY {
             // White lost all its pieces, Black won.
-            return Some(Color::Black);
+            return Some(Some(Color::Black));
         }
 
         debug_assert!(black | white | block == BitBoard::UNIVERSE);
@@ -139,12 +139,12 @@ impl PositionType for Position {
         let white_n = white.len();
 
         match black_n.cmp(&white_n) {
-            cmp::Ordering::Less => Some(Color::White),
-            cmp::Ordering::Greater => Some(Color::Black),
+            cmp::Ordering::Less => Some(Some(Color::White)),
+            cmp::Ordering::Greater => Some(Some(Color::Black)),
             // Though there can't be an equal number of black and white pieces
             // on an empty ataxx board, it is possible with an odd number of
             // blocker pieces.
-            cmp::Ordering::Equal => None,
+            cmp::Ordering::Equal => Some(None),
         }
     }
 

games/src/chess/position.rs

@@ -123,7 +123,7 @@ impl PositionType for Position {
         false
     }
 
-    fn winner(&self) -> Option<Color> {
+    fn winner(&self) -> Option<Option<Color>> {
         None
     }
 

games/src/interface/position.rs

@@ -63,7 +63,7 @@ where
 
     /// Returns the side which has won in the current position, if any.
     #[must_use]
-    fn winner(&self) -> Option<Color<Self>>;
+    fn winner(&self) -> Option<Option<Color<Self>>>;
     /// Returns `true` if the game is over in the current position.
     #[must_use]
     fn is_game_over(&self) -> bool {

games/src/isolation/position.rs

@@ -103,9 +103,9 @@ impl PositionType for Position {
         self.count_moves::<true, true>() == 0
     }
 
-    fn winner(&self) -> Option<Color> {
+    fn winner(&self) -> Option<Option<Color>> {
         if self.is_game_over() {
-            Some(!self.side_to_move)
+            Some(Some(!self.side_to_move))
         } else {
             None
         }