FA-82769 / Chess move legality / Member archive

Castling right kept after the king left the back rank · case 04

A white king on e2 still yields a castling rook.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Input: {"board", "rights"}: rights letters are K/Q (outermost own rook on the back rank on the king's h-side / a-side), file letters A-H or a-h (the own rook on that file), or "-". A right only counts if the king is on its back rank (rank 1 for white, 8 for black) and the rook exists. Return the sorted distinct list of rook squares that carry castling rights.

Why this case matters

Chess960 and X-FEN positions encode castling by rook file; a wrong mapping castles with the wrong rook.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
king off back rank	`["h1"]`	`[]`	Failed

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