Allow fifty-move claim ahead of a checkmating or stalemating move#1193
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Allow fifty-move claim ahead of a checkmating or stalemating move#1193Booyaka101 wants to merge 1 commit into
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can_claim_fifty_moves() pushed each non-zeroing legal move and tested the result with is_fifty_moves(), which is False when the resulting position has no legal moves. A move that completes the 100 halfmoves but also gives checkmate or stalemate was therefore rejected. Under FIDE 9.3 the claim is made ahead of the move: the player only declares a non-pawn, non-capture move that completes the count; it is not played, so its being game-ending does not invalidate the claim. With the clock at 99 any non-zeroing legal move completes the count, so the push/is_fifty_moves() test becomes a direct check. Positions that are already checkmate or stalemate still return False (no legal moves to iterate). Closes niklasf#1188.
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Closes #1188.
can_claim_fifty_moves()pushed each non-zeroing legal move and tested the result withis_fifty_moves(), which is False when the resulting position has no legal moves. A move that completes the 100 halfmoves but also gives checkmate or stalemate was therefore rejected.Under FIDE 9.3 the claim is made ahead of the move: the player declares a non-pawn, non-capture move that completes the count; it is not played, so its being game-ending does not invalidate the claim (confirmed in the issue thread by an FA, an IA and a National Arbiter). With the clock at 99 any non-zeroing legal move completes the count, so the push/
is_fifty_moves()test becomes a direct check. Positions that are already checkmate or stalemate still return False (no legal moves to iterate), so the existing "too late to claim" tests are unchanged.Reproducer from the issue now returns True; added a regression test. Full suite (291 tests) and
mypy --strict chess/pyright chesspass.