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Add debug assert and formatting in validate_en_passant. #1054

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Merged
codedeliveryservice merged 2 commits into from
May 30, 2026
+12 −10
Merged

Add debug assert and formatting in validate_en_passant. #1054

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3332cdc
Add debug assert and formatting in validate_en_passant.
protonspring May 28, 2026
657f7d7
revert early return
codedeliveryservice May 30, 2026
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22 changes: 12 additions & 10 deletions src/board.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -498,28 +498,30 @@ impl Board {
/// We verify is self.state.enpassant is valid, and remove it if it is not.
/// This must be called after pinners and checkers have been updated.
fn validate_en_passant(&mut self) {
if self.en_passant() == Square::None {
debug_assert!(!self.all_threats().is_empty());

let ep = self.en_passant();
if ep == Square::None {
return;
}

let stm = self.side_to_move();
let king = self.king_square(stm);
let pushed_pawn = self.en_passant() ^ 8;
let ep_occ = self.occupancies() ^ self.en_passant().to_bb() ^ pushed_pawn.to_bb();

let attackers = pawn_attacks(self.en_passant(), !stm) & self.colored_pieces(stm, PieceType::Pawn);
let ep_occ = self.occupancies() ^ ep.to_bb() ^ (ep ^ 8).to_bb();
let ep_takers = pawn_attacks(ep, !stm) & self.colored_pieces(stm, PieceType::Pawn);

for attacker in attackers {
let occ = ep_occ ^ attacker.to_bb();
let slide_attackers = (rook_attacks(king, occ) & self.pieces2(PieceType::Rook, PieceType::Queen))
for ep_taker in ep_takers {
let occ = ep_occ ^ ep_taker.to_bb();
let checkers = (rook_attacks(king, occ) & self.pieces2(PieceType::Rook, PieceType::Queen))
| (bishop_attacks(king, occ) & self.pieces2(PieceType::Bishop, PieceType::Queen));

if (slide_attackers & self.colors(!stm)).is_empty() {
if (checkers & self.colors(!stm)).is_empty() {
// En passant capture is allowed
return;
}
}

self.state.keys.toggle_en_passant(self.en_passant());
self.state.keys.toggle_en_passant(ep);
self.state.en_passant = Square::None;
}

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