Decompose ObjectKind.String and doMotion (refactor step 7)

String's tail moves into stringRest; doMotion's erase step moves into
eraseFlight and the inverted loop drops a nesting level. Behavior
unchanged.

game/object.go

@@ -77,17 +77,9 @@ func (k ObjectKind) String() string {
 		return "suit of armor"
 	case KindRing:
 		return ringName
-	case KindWand:
+	default:
-		return "wand or staff"
+		return k.stringRest()
-	case KindAmulet:
-		return "amulet"
-	case KindGold:
-		return goldName
-	case KindRingOrStick:
-		return "ring, wand or staff"
 	}
-
-	return "bizarre thing"
 }
 
 // objectKindForGlyph is the reverse of Glyph: what category of item does a
@@ -123,6 +115,23 @@ func (k ObjectKind) MergesInPack() bool {
 	return k == KindPotion || k == KindScroll || k == KindFood
 }
 
+// stringRest names the remaining kinds, including the ring-or-stick
+// prompt pseudo-kind (the tail of the C type_name switch).
+func (k ObjectKind) stringRest() string {
+	switch k {
+	case KindWand:
+		return "wand or staff"
+	case KindAmulet:
+		return "amulet"
+	case KindGold:
+		return goldName
+	case KindRingOrStick:
+		return "ring, wand or staff"
+	}
+
+	return "bizarre thing"
+}
+
 // Object is the _o arm of the C THING union: anything that can lie on the
 // floor or ride in a pack.
 type Object struct {

game/weapons.go

@@ -35,32 +35,36 @@ func (g *RogueGame) doMotion(obj *Object, ydelta, xdelta int) {
 	// Come fly with us ...
 	obj.Pos = p.Pos
 	for {
-		// Erase the old one
+		g.eraseFlight(obj, p.Pos)
-		if obj.Pos != p.Pos && g.canSee(obj.Pos.Y, obj.Pos.X) && !g.Options.Terse {
+		// Get the new position
+		obj.Pos.Y += ydelta
+		obj.Pos.X += xdelta
+
+		ch := g.Level.VisibleChar(obj.Pos.Y, obj.Pos.X)
+		if !stepOk(ch) || ch == Door {
+			break
+		}
+		// It hasn't hit anything yet, so display it if it's alright.
+		if g.canSee(obj.Pos.Y, obj.Pos.X) && !g.Options.Terse {
+			g.mvaddch(obj.Pos.Y, obj.Pos.X, obj.Kind.Glyph())
+			g.refresh()
+		}
+	}
+}
+
+// eraseFlight erases a flying object from its current square, unless it
+// still sits on the hero (the erase step of weapons.c do_motion).
+func (g *RogueGame) eraseFlight(obj *Object, heroPos Coord) {
+	if obj.Pos == heroPos || !g.canSee(obj.Pos.Y, obj.Pos.X) || g.Options.Terse {
+		return
+	}
+
 	ch := g.Level.Char(obj.Pos.Y, obj.Pos.X)
 	if ch == Floor && !g.showFloor() {
 		ch = ' '
 	}
 
 	g.mvaddch(obj.Pos.Y, obj.Pos.X, ch)
-		}
-		// Get the new position
-		obj.Pos.Y += ydelta
-		obj.Pos.X += xdelta
-
-		ch := g.Level.VisibleChar(obj.Pos.Y, obj.Pos.X)
-		if stepOk(ch) && ch != Door {
-			// It hasn't hit anything yet, so display it if it's alright.
-			if g.canSee(obj.Pos.Y, obj.Pos.X) && !g.Options.Terse {
-				g.mvaddch(obj.Pos.Y, obj.Pos.X, obj.Kind.Glyph())
-				g.refresh()
-			}
-
-			continue
-		}
-
-		break
-	}
 }
 
 // fall drops an item someplace around here (weapons.c fall).