fix pull request #340 - untrap steed sanity

When a failed #untrap attempt while mounted caused hero to be moved
onto the trap, it neglected to set the steed's coordinates to match.
If 'sanity_check' was On, that would trigger warnings about steed's
anomalous position.  Eventually a normal move would put steed's
coordinates back in sync with the hero's.

The pull request code set u.usteed->{mx,my} directly.  I've used
u_on_newpos() instead.  I also replaced some direct manipulations of
u.{ux,uy} with u_on_newpos() so that if clipping is in effect it will
be updated.

Fixes #340

doc/fixes37.0

@@ -164,6 +164,8 @@ some monster code was checking whether pets or engulfers were eating green
 	slime by checking for green slime corpse instead of glob
 change light radius of stack of candles to square root
 could get redundate "mon hits other-mon" messages when mon wields an artifact
+failed untrap while mounted that moved hero onto the trap would leave steed
+	with stale coordinates, triggering warnings if 'sanity_check' is On
 
 
 Fixes to 3.7.0-x Problems that Were Exposed Via git Repository

src/hack.c

@@ -1416,8 +1416,8 @@ domove_core()
     }
     if (u.uswallow) {
         u.dx = u.dy = 0;
-        u.ux = x = u.ustuck->mx;
+        x = u.ustuck->mx, y = u.ustuck->my;
-        u.uy = y = u.ustuck->my;
+        u_on_newpos(x, y); /* set u.ux,uy and handle CLIPPING */
         mtmp = u.ustuck;
     } else {
         if (Is_airlevel(&u.uz) && rn2(4) && !Levitation && !Flying) {
@@ -1777,15 +1777,15 @@ domove_core()
     if (!in_out_region(x, y))
         return;
 
-    /* now move the hero */
     mtmp = m_at(x, y);
+    /* tentaively move the hero plus steed; leave CLIPPING til later */
     u.ux += u.dx;
     u.uy += u.dy;
-    /* Move your steed, too */
     if (u.usteed) {
         u.usteed->mx = u.ux;
         u.usteed->my = u.uy;
-        exercise_steed();
+        /* [if move attempt ends up being blocked, should training count?] */
+        exercise_steed(); /* train riding skill */
     }
 
     /*
@@ -1911,10 +1911,15 @@ domove_core()
 
         if (didnt_move) {
             u.ux = u.ux0, u.uy = u.uy0; /* didn't move after all */
+            /* could skip this bit since we're about to call u_on_newpos() */
             if (u.usteed)
                 u.usteed->mx = u.ux, u.usteed->my = u.uy;
         }
     }
+    /* tentative move above didn't handle CLIPPING, in case there was a
+       monster in the way and the move attempt ended up being blocked;
+       do a full re-position now, possibly back to where hero started */
+    u_on_newpos(u.ux, u.uy);
 
     reset_occupations();
     if (g.context.run) {

src/trap.c

@@ -4035,7 +4035,8 @@ struct trap *ttmp;
     if (!Punished
         || drag_ball(x, y, &bc, &bx, &by, &cx, &cy, &unused, TRUE)) {
         u.ux0 = u.ux, u.uy0 = u.uy;
-        u.ux = x, u.uy = y;
+        /* set u.ux,u.uy and u.usteed->mx,my plus handle CLIPPING */
+        u_on_newpos(x, y);
         u.umoved = TRUE;
         newsym(u.ux0, u.uy0);
         vision_recalc(1);