Give item categories and subtypes real types (refactor step 2)

ObjectKind separates what an item is from how it draws: Object.Type
(a byte that doubled as the map character) becomes Kind ObjectKind,
with Glyph() producing the display character and objectKindForGlyph
converting back at the map boundary. KindWand covers the C 'stick'
category. The magic-missile bolt uses KindGold, matching C's literal
o_type='*' trick, with a comment.

PotionKind, ScrollKind, RingKind, WandKind, WeaponKind, ArmorKind and
TrapKind are now iota enums with Stringer (names come from the base
info tables); Object gains typed accessors (obj.RingKind(), ...) and
Launch is typed WeaponKind. beTrapped returns TrapKind. The
getItem/inventory/whatis prompt filters take ObjectKind, with
KindCallable/KindRingOrStick replacing the C CALLABLE/R_OR_S
sentinels; wizard.c's type_name table is subsumed by
ObjectKind.String(). IsRing/IsWearing/initWeapon/doPot signatures are
typed accordingly.

The save format version becomes 5.4.4-go2: the gob field rename would
otherwise silently zero Kind when reading old saves.

No behavior change; full suite green.

game/things.go

@@ -13,14 +13,14 @@ func (g *RogueGame) invName(obj *Object, drop bool) string {
 	var pb strings.Builder
 	which := obj.Which
 	it := &g.Items
-	switch obj.Type {
-	case Potion:
+	switch obj.Kind {
+	case KindPotion:
 		g.nameit(&pb, obj, "potion", it.PotColors[which], &it.Potions[which], nullstr)
-	case Ring:
+	case KindRing:
 		g.nameit(&pb, obj, "ring", it.RingStones[which], &it.Rings[which], ringNum)
-	case Stick:
+	case KindWand:
 		g.nameit(&pb, obj, it.WandType[which], it.WandMade[which], &it.Sticks[which], chargeStr)
-	case Scroll:
+	case KindScroll:
 		if obj.Count == 1 {
 			pb.WriteString("A scroll ")
 		} else {
@@ -34,7 +34,7 @@ func (g *RogueGame) invName(obj *Object, drop bool) string {
 		} else {
 			fmt.Fprintf(&pb, "titled '%s'", it.ScrNames[which])
 		}
-	case Food:
+	case KindFood:
 		if which == 1 {
 			if obj.Count == 1 {
 				fmt.Fprintf(&pb, "A%s %s", vowelstr(g.Fruit), g.Fruit)
@@ -48,7 +48,7 @@ func (g *RogueGame) invName(obj *Object, drop bool) string {
 				fmt.Fprintf(&pb, "%d rations of food", obj.Count)
 			}
 		}
-	case Weapon:
+	case KindWeapon:
 		sp := it.Weapons[which].Name
 		if obj.Count > 1 {
 			fmt.Fprintf(&pb, "%d ", obj.Count)
@@ -66,7 +66,7 @@ func (g *RogueGame) invName(obj *Object, drop bool) string {
 		if obj.Label != "" {
 			fmt.Fprintf(&pb, " called %s", obj.Label)
 		}
-	case Armor:
+	case KindArmor:
 		sp := it.Armors[which].Name
 		if obj.Flags.Has(Known) {
 			fmt.Fprintf(&pb, "%s %s [", num(aClass[which]-obj.Arm, 0, Armor), sp)
@@ -80,9 +80,9 @@ func (g *RogueGame) invName(obj *Object, drop bool) string {
 		if obj.Label != "" {
 			fmt.Fprintf(&pb, " called %s", obj.Label)
 		}
-	case Amulet:
+	case KindAmulet:
 		pb.WriteString("The Amulet of Yendor")
-	case Gold:
+	case KindGold:
 		fmt.Fprintf(&pb, "%d Gold pieces", obj.GoldVal())
 	}
 
@@ -121,20 +121,20 @@ func (g *RogueGame) dropIt() {
 		g.msg("there is something there already")
 		return
 	}
-	obj := g.getItem("drop", 0)
+	obj := g.getItem("drop", KindNone)
 	if obj == nil {
 		return
 	}
 	if !g.dropCheck(obj) {
 		return
 	}
-	obj = g.leavePack(obj, true, !IsMult(obj.Type))
+	obj = g.leavePack(obj, true, !obj.Kind.MergesInPack())
 	// Link it into the level object list
 	attachObj(&g.Level.Objects, obj)
-	g.Level.SetChar(p.Pos.Y, p.Pos.X, obj.Type)
+	g.Level.SetChar(p.Pos.Y, p.Pos.X, obj.Kind.Glyph())
 	g.Level.FlagsAt(p.Pos.Y, p.Pos.X).Set(FDropped)
 	obj.Pos = p.Pos
-	if obj.Type == Amulet {
+	if obj.Kind == KindAmulet {
 		g.HasAmulet = false
 	}
 	g.msg("dropped %s", g.invName(obj, true))
@@ -166,7 +166,7 @@ func (g *RogueGame) dropCheck(obj *Object) bool {
 			hand = Left
 		}
 		p.CurRing[hand] = nil
-		switch obj.Which {
+		switch obj.RingKind() {
 		case RingAddStrength:
 			g.chgStr(-obj.Arm)
 		case RingSeeInvisible:
@@ -195,13 +195,13 @@ func (g *RogueGame) newThing() *Object {
 	}
 	switch kind {
 	case 0:
-		cur.Type = Potion
+		cur.Kind = KindPotion
 		cur.Which = pickOne(g, g.Items.Potions[:])
 	case 1:
-		cur.Type = Scroll
+		cur.Kind = KindScroll
 		cur.Which = pickOne(g, g.Items.Scrolls[:])
 	case 2:
-		cur.Type = Food
+		cur.Kind = KindFood
 		g.Player.NoFood = 0
 		if g.rnd(10) != 0 {
 			cur.Which = 0
@@ -209,7 +209,7 @@ func (g *RogueGame) newThing() *Object {
 			cur.Which = 1
 		}
 	case 3:
-		g.initWeapon(cur, pickOne(g, g.Items.Weapons[:NumWeaponTypes]))
+		g.initWeapon(cur, WeaponKind(pickOne(g, g.Items.Weapons[:NumWeaponTypes])))
 		if r := g.rnd(100); r < 10 {
 			cur.Flags.Set(Cursed)
 			cur.HPlus -= g.rnd(3) + 1
@@ -217,7 +217,7 @@ func (g *RogueGame) newThing() *Object {
 			cur.HPlus += g.rnd(3) + 1
 		}
 	case 4:
-		cur.Type = Armor
+		cur.Kind = KindArmor
 		cur.Which = pickOne(g, g.Items.Armors[:])
 		cur.Arm = aClass[cur.Which]
 		if r := g.rnd(100); r < 20 {
@@ -227,9 +227,9 @@ func (g *RogueGame) newThing() *Object {
 			cur.Arm -= g.rnd(3) + 1
 		}
 	case 5:
-		cur.Type = Ring
+		cur.Kind = KindRing
 		cur.Which = pickOne(g, g.Items.Rings[:])
-		switch cur.Which {
+		switch cur.RingKind() {
 		case RingAddStrength, RingProtection, RingDexterity, RingIncreaseDamage:
 			if cur.Arm = g.rnd(3); cur.Arm == 0 {
 				cur.Arm = -1
@@ -239,7 +239,7 @@ func (g *RogueGame) newThing() *Object {
 			cur.Flags.Set(Cursed)
 		}
 	case 6:
-		cur.Type = Stick
+		cur.Kind = KindWand
 		cur.Which = pickOne(g, g.Items.Sticks[:])
 		g.fixStick(cur)
 	}
@@ -336,7 +336,7 @@ func (g *RogueGame) printDisc(typ byte) {
 	numFound := 0
 	for i := range info {
 		if info[order[i]].Know || info[order[i]].Guess != "" {
-			obj.Type = typ
+			obj.Kind = objectKindForGlyph(typ)
 			obj.Which = order[i]
 			g.addLine("%s", g.invName(&obj, false))
 			numFound++