filled trap doors on castle can be re-dug

doc/fixes35.0

@@ -72,6 +72,7 @@ mimic should not mimic a boulder while on a pit or hole location
 reviving invisible troll could appear visible until it moves
 adjust some of the shop repair messages
 charge for reviving a shop owned corpse or reanimating a shop owned statue
+filled trap doors on castle can be re-dug
 
 
 Platform- and/or Interface-Specific Fixes

include/rm.h

@@ -340,6 +340,7 @@ struct rm {
 	Bitfield(waslit,1);	/* remember if a location was lit */
 	Bitfield(roomno,6);	/* room # for special rooms */
 	Bitfield(edge,1);	/* marks boundaries for special rooms*/
+	Bitfield(candig,1);	/* Exception to Can_dig_down; was a trapdoor */
 };
 
 /*

src/apply.c

@@ -2839,7 +2839,8 @@ do_break_wand(obj)
 			fillmsg = TRUE;
 		} else
 			digactualhole(x, y, BY_OBJECT,
-			      (rn2(obj->spe) < 3 || !Can_dig_down(&u.uz)) ?
+			      (rn2(obj->spe) < 3 ||
+				(!Can_dig_down(&u.uz) && !levl[x][y].candig)) ?
 			       PIT : HOLE);
 	    }
 	    continue;

src/dig.c

@@ -186,7 +186,8 @@ dig_check(madeby, verbose, x, y)
 	} else if ((IS_ROCK(levl[x][y].typ) && levl[x][y].typ != SDOOR &&
 		      (levl[x][y].wall_info & W_NONDIGGABLE) != 0)
 		|| (ttmp &&
-		      (ttmp->ttyp == MAGIC_PORTAL || !Can_dig_down(&u.uz)))) {
+		      (ttmp->ttyp == MAGIC_PORTAL ||
+			(!Can_dig_down(&u.uz) && !levl[x][y].candig)))) {
 	    if(verbose) pline_The("%s here is too hard to %s.",
 				  surface(x,y), verb);
 	    return(FALSE);
@@ -513,7 +514,7 @@ int ttyp;
 	    return;
 	}
 
-	if (ttyp != PIT && !Can_dig_down(&u.uz)) {
+	if (ttyp != PIT && (!Can_dig_down(&u.uz) && !lev->candig)) {
 	    impossible("digactualhole: can't dig %s on this level.",
 		       defsyms[trap_to_defsym(ttyp)].explanation);
 	    ttyp = PIT;
@@ -676,7 +677,7 @@ boolean pit_only;
 	struct rm *lev = &levl[u.ux][u.uy];
 	struct obj *boulder_here;
 	schar typ;
-	boolean nohole = !Can_dig_down(&u.uz);
+	boolean nohole = (!Can_dig_down(&u.uz) && !lev->candig);
 
 	if ((ttmp && (ttmp->ttyp == MAGIC_PORTAL || nohole)) ||
 	   (IS_ROCK(lev->typ) && lev->typ != SDOOR &&

src/hack.c

@@ -174,6 +174,8 @@ moverock()
 		    deltrap(ttmp);
 		    delobj(otmp);
 		    bury_objs(rx, ry);
+		    levl[rx][ry].wall_info &= ~W_NONDIGGABLE;
+		    levl[rx][ry].candig = 1;
 		    if (cansee(rx,ry)) newsym(rx,ry);
 		    continue;
 		case LEVEL_TELEP:

src/muse.c

@@ -655,7 +655,7 @@ mon_tele:
 			pline_The("digging ray is ineffective.");
 			return 2;
 		}
-		if (!Can_dig_down(&u.uz)) {
+		if (!Can_dig_down(&u.uz) && !levl[mtmp->mx][mtmp->my].candig) {
 		    if(canseemon(mtmp))
 			pline_The("%s here is too hard to dig in.",
 					surface(mtmp->mx, mtmp->my));

src/trap.c

@@ -333,7 +333,8 @@ boolean td;	/* td == TRUE : trap door or hole */
 
 	if (In_sokoban(&u.uz) && Can_fall_thru(&u.uz))
 	    ;	/* KMH -- You can't escape the Sokoban level traps */
-	else if(Levitation || u.ustuck || !Can_fall_thru(&u.uz)
+	else if(Levitation || u.ustuck
+	   || (!Can_fall_thru(&u.uz) && !levl[u.ux][u.uy].candig)
 	   || Flying || is_clinger(youmonst.data)
 	   || (Inhell && !u.uevent.invoked &&
 					newlevel == dunlevs_in_dungeon(&u.uz))