fix #H6338 - naming mimicked potion

Player tried to #name a potion on the floor and got prompted to call a
stream of fluid (sink feedback) instead of a potion.  A mimic posing
as an object is represented by a partially initialized object when
examining its map location.  #name for floor object uses the same data
as look_at.

obj->fromsink overloads obj->corpsenm which is set to NON_PM (-1) even
when creating a non-init'd object.  'fromsink' was only being forced to
0 when creating an init'd object (unlike leash which has its overload
of corpsenm set properly regardless of caller's request to init).  So
docall() treated a mimicked potion as a sink stream.

The fix is straightforward but has pointed out another bug which is
harder to fix.  Examining a floor object next to you sets that obj's
dknown flag as if you had seen it up close (a new feature in 3.6.0).
But a mimicked item is discarded as soon as it's been looked at, so
looking again from a non-adjacent spot will give different feedback
since the previously set dknown will be unset when replaced by a new
fake object.  So you can use '/' and ';' to recognize mimics without
provoking them into motion.  Best fix:  mimicking an object should use
a fully initialized one which is tracked via monst->mextra, but that
will break save file compatibility.  Possible hack:  change monst->
mappearance into a mask which uses N bits for object type (instead of
full 'int') and one of the other bits to track obj->dknown.  Examining
an adjacent object probably ought to set bknown for priests, so bknown
and blessed/uncursed/cursed would need to be tracked too.

doc/fixes36.1

@@ -464,6 +464,8 @@ improve #adjust command's handling of the '$' and '#' inventory slots
 prevent #adjust from allowing anything to be moved into the special '-' slot
 sometimes rings dropped into sinks can be found in the pipes
 doors in special levels were always generated in vertical orientation
+assigning a type name to a potion on the floor which is actually a mimic could
+	prompt "Call a stream of <potion-type> fluid:" (bogus 'fromsink')
 
 
 Fixes to Post-3.6.0 Problems that Were Exposed Via git Repository

src/mkobj.c

@@ -223,6 +223,7 @@ boolean init, artif;
     return otmp;
 }
 
+/* mkobj(): select a type of item from a class, use mksobj() to create it */
 struct obj *
 mkobj(oclass, artif)
 char oclass;
@@ -277,7 +278,7 @@ struct obj *box;
             n = 0;
             break;
         }
-    /*else FALLTHRU*/
+        /*else FALLTHRU*/
     case BAG_OF_HOLDING:
         n = 1;
         break;
@@ -712,6 +713,7 @@ static const char dknowns[] = { WAND_CLASS,   RING_CLASS, POTION_CLASS,
                                 SCROLL_CLASS, GEM_CLASS,  SPBOOK_CLASS,
                                 WEAPON_CLASS, TOOL_CLASS, 0 };
 
+/* mksobj(): create a specific type of object */
 struct obj *
 mksobj(otyp, init, artif)
 int otyp;
@@ -743,7 +745,7 @@ boolean artif;
     otmp->cknown = 0;
     otmp->corpsenm = NON_PM;
 
-    if (init)
+    if (init) {
         switch (let) {
         case WEAPON_CLASS:
             otmp->quan = is_multigen(otmp) ? (long) rn1(6, 6) : 1L;
@@ -773,9 +775,8 @@ boolean artif;
                        && (--tryct > 0));
                 if (tryct == 0) {
                     /* perhaps rndmonnum() only wants to make G_NOCORPSE
-                       monsters on
+                       monsters on this level; create an adventurer's
-                       this level; let's create an adventurer's corpse
+                       corpse instead, then */
-                       instead, then */
                     otmp->corpsenm = PM_HUMAN;
                 }
                 /* timer set below */
@@ -889,14 +890,13 @@ boolean artif;
             case BAG_OF_TRICKS:
                 otmp->spe = rnd(20);
                 break;
-            case FIGURINE: {
+            case FIGURINE:
-                int tryct2 = 0;
+                tryct = 0;
                 do
                     otmp->corpsenm = rndmonnum();
-                while (is_human(&mons[otmp->corpsenm]) && tryct2++ < 30);
+                while (is_human(&mons[otmp->corpsenm]) && tryct++ < 30);
                 blessorcurse(otmp, 4);
                 break;
-            }
             case BELL_OF_OPENING:
                 otmp->spe = 3;
                 break;
@@ -918,15 +918,12 @@ boolean artif;
                 curse(otmp);
             } else
                 blessorcurse(otmp, 10);
+            break;
         case VENOM_CLASS:
         case CHAIN_CLASS:
         case BALL_CLASS:
             break;
-        case POTION_CLASS:
+        case POTION_CLASS: /* note: potions get some additional init below */
-            otmp->fromsink = 0;
-            if (otmp->otyp == POT_OIL)
-                otmp->age = MAX_OIL_IN_FLASK; /* amount of oil */
-        /* fall through */
         case SCROLL_CLASS:
 #ifdef MAIL
             if (otmp->otyp != SCR_MAIL)
@@ -1012,27 +1009,36 @@ boolean artif;
                        objects[otmp->otyp].oc_class);
             return (struct obj *) 0;
         }
+    }
 
     /* some things must get done (corpsenm, timers) even if init = 0 */
-    switch (otmp->otyp) {
+    switch ((otmp->oclass == POTION_CLASS && otmp->otyp != POT_OIL)
+            ? POT_WATER
+            : otmp->otyp) {
     case CORPSE:
         if (otmp->corpsenm == NON_PM) {
             otmp->corpsenm = undead_to_corpse(rndmonnum());
             if (mvitals[otmp->corpsenm].mvflags & (G_NOCORPSE | G_GONE))
                 otmp->corpsenm = urole.malenum;
         }
-    /*FALLTHRU*/
+        /*FALLTHRU*/
     case STATUE:
     case FIGURINE:
         if (otmp->corpsenm == NON_PM)
             otmp->corpsenm = rndmonnum();
-    /*FALLTHRU*/
+        /*FALLTHRU*/
     case EGG:
-        /* case TIN: */
+    /* case TIN: */
         set_corpsenm(otmp, otmp->corpsenm);
         break;
+    case POT_OIL:
+        otmp->age = MAX_OIL_IN_FLASK; /* amount of oil */
+        /*FALLTHRU*/
+    case POT_WATER: /* POTION_CLASS */
+        otmp->fromsink = 0; /* overloads corpsenm, which was set to NON_PM */
+        break;
     case LEASH:
-        otmp->leashmon = 0;
+        otmp->leashmon = 0; /* overloads corpsenm, which was set to NON_PM */
         break;
     case SPE_NOVEL:
         otmp->novelidx = -1; /* "none of the above"; will be changed */

src/pager.c

@@ -195,7 +195,7 @@ struct obj **obj_p;
            glyph among floor and buried objects; when !Blind, any buried
            object's glyph will have been replaced by whatever is present
            on the surface as soon as we moved next to its spot */
-        && otmp->where == OBJ_FLOOR /* not buried */
+        && (fakeobj || otmp->where == OBJ_FLOOR) /* not buried */
         /* terrain mode views what's already known, doesn't learn new stuff */
         && !iflags.terrainmode) /* so don't set dknown when in terrain mode */
         otmp->dknown = 1; /* if a pile, clearly see the top item only */