Fix legality testing of drop moves

Drops of noexistent pieces (i.e. with a piece indicator letter that is
not corresponding to any defined piece) are now parsed as
ImpossibleMove, rather than IllegalMove, so they are also rejected with
legality testing off.

diff --git a/parser.l b/parser.l
index 061d6ca..7188823 100644 (file)
--- a/parser.l
+++ b/parser.l
@@ -845,6 +845,8 @@ extern void CopyBoard P((Board to, Board from));
     } else {
        currentMoveString[0] = ToLower(yytext[0]);
     }
+    if(CharToPiece(currentMoveString[0]) == EmptySquare) return ImpossibleMove; // Unknown piece;
+
     return LegalityTest(boards[yyboardindex], PosFlags(yyboardindex), DROP_RANK, // [HGM] does drops now too
                         CharToPiece(currentMoveString[0]), currentMoveString[3] - ONE, currentMoveString[2] - AAA, NULLCHAR);
 }