FA-82538 / Chess move legality / Member archive

File check walked as a diagonal · case 03

Interposing on the checking file is rejected while unrelated diagonal squares are accepted.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Input: {"board", "move": [from, to]} for a non-king piece whose king may be in check (pins are ignored). Return true if the move is allowed by the check rules: no check means true; double check means false; a single check is answered by capturing the checker or, for a rook, bishop or queen checker, by moving onto a square strictly between it and the king.

Why this case matters

Move validators gate every move in engines, servers and arbiters; accepting an illegal move or rejecting a legal one corrupts the game record.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
interpose on file	`false`	`true`	Failed

MEMBER ARCHIVE

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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