Fix illegal drops

For illegal drops the 'from-square' was subjected to an on-board test,
which of course always failed, after which the move was reclassified
as an ImpossibleMove after all. (Leading to rejection even when legality
testing was off, and error messages like "Could not parse move".)

diff --git a/backend.c b/backend.c
index 6bf57ac..9a9d0a4 100644 (file)
--- a/backend.c
+++ b/backend.c
@@ -5494,6 +5494,7 @@ char yy_textstr[8000];
 Boolean
 ParseOneMove (char *move, int moveNum, ChessMove *moveType, int *fromX, int *fromY, int *toX, int *toY, char *promoChar)
 {
+    int badFrom;
     *moveType = yylexstr(moveNum, move, yy_textstr, sizeof yy_textstr);
 
     switch (*moveType) {
@@ -5525,7 +5526,9 @@ ParseOneMove (char *move, int moveNum, ChessMove *moveType, int *fromX, int *fro
         *toX = currentMoveString[2] - AAA;
         *toY = currentMoveString[3] - ONE;
        *promoChar = currentMoveString[4];
-        if (*fromX < BOARD_LEFT || *fromX >= BOARD_RGHT || *fromY < 0 || *fromY >= BOARD_HEIGHT ||
+       badFrom = (*fromX < BOARD_LEFT || *fromX >= BOARD_RGHT || *fromY < 0 || *fromY >= BOARD_HEIGHT);
+       if(currentMoveString[1] == '@') { badFrom = FALSE; *fromX = CharToPiece(currentMoveString[0]); *fromY = DROP_RANK; } // illegal drop
+        if (badFrom ||
             *toX < BOARD_LEFT || *toX >= BOARD_RGHT || *toY < 0 || *toY >= BOARD_HEIGHT) {
     if (appData.debugMode) {
         fprintf(debugFP, "Off-board move (%d,%d)-(%d,%d)%c, type = %d\n", *fromX, *fromY, *toX, *toY, *promoChar, *moveType);