FA-82510 / Chess move legality / Member archive

Bishop on the king's file pins a knight · case 05

A knight between its king and an enemy bishop on the same file may not move.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Input: {"board", "from": square of a non-king piece, "to": its pseudo-legal destination}. Return false only when the piece is absolutely pinned (it is the first piece on a line from its own king and the next piece beyond it on that line is an enemy rook/queen on a rank or file, or bishop/queen on a diagonal) and the destination leaves that line; moves along the pin line, including capturing the pinner, return true.

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
bishop on file is not a pinner	`false`	`true`	Failed

MEMBER ARCHIVE

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