cheng: Fix captures not reseting half move clock

cheng/src/board/borked.rs

@@ -131,15 +131,7 @@ impl BorkedBoard {
             pawn_pieces.reset(actual_pawn_square);
         }
 
-        self.side_mut(self.turn.opposite())
-            .remove(movement.destination);
-
-        self.white_side.update_threats(&self.black_side);
-        self.black_side.update_threats(&self.white_side);
-
-        self.white_side.update_king_in_check(&self.black_side);
-        self.black_side.update_king_in_check(&self.white_side);
-
+        // This handles en passant capture as well.
         if piece_is_pawn
             || self
                 .side(self.turn.opposite())
@@ -155,6 +147,15 @@ impl BorkedBoard {
             self.fullmove_clock += 1;
         }
 
+        self.side_mut(self.turn.opposite())
+            .remove(movement.destination);
+
+        self.white_side.update_threats(&self.black_side);
+        self.black_side.update_threats(&self.white_side);
+
+        self.white_side.update_king_in_check(&self.black_side);
+        self.black_side.update_king_in_check(&self.white_side);
+
         self.turn = self.turn.opposite();
     }
 

cheng/tests/correctness_game_result.rs

@@ -14,6 +14,17 @@ fn correctness_game_result_50_move_draw() {
     board.try_feed("f5e5").unwrap_err();
 }
 
+#[test]
+fn correctness_game_result_50_move_draw_capture() {
+    // https://lichess.org/analysis/fromPosition/4k3/8/8/1p6/8/2b5/3N4/4K3_b_-_-_99_1
+    cheng::init();
+
+    let mut board = Board::from_fen("4k3/8/8/1p6/8/2b5/3N4/4K3 b - - 99 1").unwrap();
+    board.try_feed("c3d2").unwrap();
+
+    assert_eq!(board.result(), GameResult::Undecided);
+}
+
 #[test]
 fn correctness_game_result_stalemate() {
     // https://lichess.org/analysis/7k/8/8/6Q1/8/8/8/4K3_w_-_-_0_1?color=white