display former possessions of dead monster

Reported directly to devteam by a hardfought player and also by
entrez.  The recent mon_leaving_level() change resulted in objects
dropped by a dying monster not being displayed immediately.

It justed needed the relobj(mon, 0, FALSE) to relobj(mon, 1, FALSE)
change in m_detach() but this does some related cleanup in
mon_leaving_level()'s callers.  wormgone() takes a long worm off the
map but leaves its stale coordinates set because some code relied on
that.  This takes away the need for that but still doesn't actually
clear them.

This adds redundant 'return' statements at the end of a few void
functions that are longer than fits within a typical screen display.
They make searching for the end of the current routine in an editor
or pager easier without resorting to regular expressions and can
also be used to search for the beginning if/when preceding routine
ends in 'return' too.

src/mon.c

@@ -1,4 +1,4 @@
-/* NetHack 3.7	mon.c	$NHDT-Date: 1651886997 2022/05/07 01:29:57 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.424 $ */
+/* NetHack 3.7	mon.c	$NHDT-Date: 1652478356 2022/05/13 21:45:56 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.426 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /*-Copyright (c) Derek S. Ray, 2015. */
 /* NetHack may be freely redistributed.  See license for details. */
@@ -2322,6 +2322,10 @@ mon_leaving_level(struct monst *mon)
             remove_worm(mon);
         else
             remove_monster(mx, my);
+
+        mon->mx = mon->my = 0; /* off normal map; if caller wants to use
+                                * mon's coordinates after this, it must
+                                * save those before calling us */
     }
     if (onmap) {
         mon->mundetected = 0; /* for migration; doesn't matter for death */
@@ -2344,13 +2348,23 @@ m_detach(
     struct monst *mtmp,
     struct permonst *mptr) /* reflects mtmp->data _prior_ to mtmp's death */
 {
+    xchar mx = mtmp->mx, my = mtmp->my;
+
     if (mtmp->mleashed)
         m_unleash(mtmp, FALSE);
 
     if (mtmp->mx > 0 && emits_light(mptr))
         del_light_source(LS_MONSTER, monst_to_any(mtmp));
 
-    /* take mtmp off map but not out of fmon list yet (dmonsfree does that) */
+    /*
+     * Take mtmp off map but not out of fmon list yet (dmonsfree does that).
+     *
+     * Sequencing issue:  mtmp's inventory should be dropped before taking
+     * it off the map but if that includes a boulder and mtmp is at a pit
+     * location, dropping minvent ought to be deferred until its corpse
+     * gets placed.  We compromise and just make sure mtmp is off the map
+     * before dropping its former belongings.
+     */
     mon_leaving_level(mtmp);
 
     mtmp->mhp = 0; /* simplify some tests: force mhp to 0 */
@@ -2362,8 +2376,13 @@ m_detach(
         leaddead();
     if (mtmp->m_id == g.stealmid)
         thiefdead();
-    /* release (drop onto map) all objects carried by mtmp */
-    relobj(mtmp, 0, FALSE);
+    /* release (drop onto map) all objects carried by mtmp; first,
+       temporarily restore mtmp's internal location (without actually
+       putting it back on the map) because relobj() relies on that but
+       mon_leaving_level() just cleared that */
+    mtmp->mx = mx, mtmp->my = my;
+    relobj(mtmp, 1, FALSE); /* drop mtmp->minvent, then issue newsym(mx,my) */
+    mtmp->mx = mtmp->my = 0;
 
     if (mtmp->isshk)
         shkgone(mtmp);
@@ -2842,6 +2861,7 @@ monstone(struct monst* mdef)
             You("%s through an opening in the new %s.",
                 u_locomotion("jump"), xname(otmp));
     }
+    return;
 }
 
 /* another monster has killed the monster mdef */
@@ -2886,6 +2906,7 @@ monkilled(
         if (rxt)
             pline("May %s %s in peace.", noit_mon_nam(mdef), rxt);
     }
+    return;
 }
 
 void
@@ -3159,6 +3180,7 @@ xkilled(
 
     /* malign was already adjusted for u.ualign.type and randomization */
     adjalign(mtmp->malign);
+    return;
 }
 
 /* changes the monster into a stone monster of the same type
@@ -4483,8 +4505,11 @@ newcham(
         *p = '\0';
 
     if (mtmp->wormno) { /* throw tail away */
-        wormgone(mtmp);
-        place_monster(mtmp, mtmp->mx, mtmp->my);
+        xchar mx = mtmp->mx, my = mtmp->my;
+
+        wormgone(mtmp); /* discards tail segments, takes head off the map */
+        /* put the head back; it will morph into mtmp's new form */
+        place_monster(mtmp, mx, my);
     }
     if (M_AP_TYPE(mtmp) && mdat->mlet != S_MIMIC)
         seemimic(mtmp); /* revert to normal monster */