Chess960 castling bug (K-C1, R-A1)

CHANGELOG.md

@@ -1,6 +1,7 @@
 ### 1.4.1
 - **Potentially breaking**: FEN strings without castling rights specified now default to no castling rights, instead of all castling rights (thanks @govind-maheshwari2).
 - Fixed Seirawan chess mating conditions not taking `H` and `E` into account (thanks @malaschitz).
+- Fixed Chess960 castling moves not working in some cases where the rook would land on the square after the king (thanks @malaschitz).
 
 ### 1.4.0
 - Custom move generation and processing (beta):

lib/src/game/game.dart

@@ -433,7 +433,7 @@ class Game {
             for (int j = 1; j <= numRookMidSquares; j++) {
               int midFile = rookFile + (i == 0 ? -j : j);
               int midSq = size.square(midFile, royalRank);
-              if (board[midSq].isNotEmpty) {
+              if (board[midSq].isNotEmpty && midFile != royalFile) {
                 valid = false;
                 break;
               }

test/misc_test.dart

@@ -100,4 +100,13 @@ void main() {
       ),
     );
   });
+  test('Chess960 K-C1:R-A1 castling', () {
+    final g = Game(
+      variant: CommonVariants.chess960(),
+      fen: 'rnkqbbrn/pppppppp/8/8/8/8/PPPPPPPP/R1K1BBRN w AGag - 0 1',
+    );
+    final moves = g.generateLegalMoves();
+    expect(moves.castlingMoves.length, 1);
+    expect(moves.from(g.size.squareNumber('c1')).length, 3);
+  });
 }