discoverying water walking boots

If water walking boots haven't been discovered yet and underwater
hero rises to the surface when putting a pair on, discover them.

(Sinking while removing such on water already discovers them.)

doc/fixes3-7-0.txt

@@ -959,6 +959,8 @@ a hero on the quest home level who runs or travels past the quest leader and
 	gets tossed out of the quest for some reason would keep running on the
 	far side of the quest portal
 allow rush/run over water if wearing discovered water walking boots
+wearing water walking boots while underwater (maybe via magical breathing)
+	and rising to surface wasn't causing the boots to become discovered
 flying pets wouldn't target underwater food but if they happened to fly over
 	such food they could and would eat it
 praying on an altar with pet corpse on it can revive the pet

include/decl.h

@@ -1044,6 +1044,9 @@ struct instance_globals_w {
     int warn_obj_cnt; /* count of monsters meeting criteria */
     long wailmsg;
 
+    /* do_wear.c */
+    uint8 wasinwater;
+
     /* symbols.c */
     nhsym warnsyms[WARNCOUNT]; /* the current warning display symbols */
 

src/decl.c

@@ -851,6 +851,8 @@ static const struct instance_globals_w g_init_w = {
     /* decl.c */
     0, /* warn_obj_cnt */
     0L, /* wailmsg */
+    /* do_wear.c */
+    0U,
     /* symbols.c */
     DUMMY, /* warnsyms */
     /* files.c */

src/do_wear.c

@@ -196,8 +196,22 @@ Boots_on(void)
     case KICKING_BOOTS:
         break;
     case WATER_WALKING_BOOTS:
+        /*
+         * Sequencing issue?  If underwater (perhaps via magical breathing),
+         * putting on water walking boots produces "you slowly rise above
+         * the surface" then "you finish your dressing maneuver".
+         */
+
+        /* spoteffects() doesn't get called here; pooleffects() is called
+           during movement and u.uinwater is already False after setworn() */
         if (u.uinwater)
             spoteffects(TRUE);
+        /* init'd in accessory_or_armor_on() and only used here */
+        if (gw.wasinwater) {
+            if (!u.uinwater)
+                makeknown(WATER_WALKING_BOOTS);
+            gw.wasinwater = 0U;
+        }
         /* (we don't need a lava check here since boots can't be
            put on while feet are stuck) */
         break;
@@ -2338,6 +2352,7 @@ accessory_or_armor_on(struct obj *obj)
          *
         obj->known = 1;
          */
+        gw.wasinwater = u.uinwater; /* for WWALKING; Boots_on() is too late */
         setworn(obj, mask);
         /* if there's no delay, we'll execute 'afternmv' immediately */
         if (obj == uarm)
@@ -2367,6 +2382,8 @@ accessory_or_armor_on(struct obj *obj)
             on_msg(obj);
         }
         svc.context.takeoff.mask = svc.context.takeoff.what = 0L;
+        /* gw.wasinwater = 0U; // can't clear this yet; Boots_on() needs it
+         * and gets called via afternmv() after this routine has returned */
     } else { /* not armor */
         if (ring) {
             /* Ring_on() expects ring to already be worn as uleft or uright */