Introduce Target.Type property.

OpenRA.Game/GameRules/WeaponInfo.cs

@@ -151,12 +151,10 @@ namespace OpenRA.GameRules
 
 		public bool IsValidAgainst(Target target, World world)
 		{
-			if (!target.IsValid)
+			if (target.Type == TargetType.Actor)
-				return false;
-
-			if (target.IsActor)
 				return IsValidAgainst(target.Actor);
-			else
+
+			if (target.Type == TargetType.Terrain)
 			{
 				var cell = target.CenterPosition.ToCPos();
 				if (ValidTargets.Contains("Ground") && world.GetTerrainType(cell) != "Water")
@@ -167,6 +165,8 @@ namespace OpenRA.GameRules
 
 				return false;
 			}
+
+			return false;
 		}
 	}
 }

OpenRA.Game/Traits/DrawLineToTarget.cs

@@ -109,8 +109,10 @@ namespace OpenRA.Traits
 
 			self.World.AddFrameEndTask(w =>
 			{
-				if (self.Destroyed) return;
+				if (self.Destroyed)
-				if (target.IsActor && display)
+					return;
+
+				if (target.Type == TargetType.Actor && display)
 					w.Add(new FlashTarget(target.Actor));
 
 				var line = self.TraitOrDefault<DrawLineToTarget>();

OpenRA.Game/Traits/Target.cs

@@ -14,18 +14,19 @@ using System.Linq;
 
 namespace OpenRA.Traits
 {
+	public enum TargetType { Invalid, Actor, Terrain }
 	public struct Target
 	{
-		public static readonly Target[] NoTargets = {};
+		public static readonly Target[] None = {};
-		public static readonly Target None = new Target();
+		public static readonly Target Invalid = new Target { type = TargetType.Invalid };
 
+		TargetType type;
 		Actor actor;
 		WPos pos;
-		bool valid;
 		int generation;
 
-		public static Target FromPos(WPos p) { return new Target { pos = p, valid = true }; }
+		public static Target FromPos(WPos p) { return new Target { pos = p, type = TargetType.Terrain }; }
-		public static Target FromCell(CPos c) { return new Target { pos = c.CenterPosition, valid = true }; }
+		public static Target FromCell(CPos c) { return new Target { pos = c.CenterPosition, type = TargetType.Terrain }; }
 		public static Target FromOrder(Order o)
 		{
 			return o.TargetActor != null
@@ -38,23 +39,39 @@ namespace OpenRA.Traits
 			return new Target
 			{
 				actor = a,
-				valid = (a != null),
+				type = a != null ? TargetType.Actor : TargetType.Invalid,
 				generation = a.Generation,
 			};
 		}
 
-		public bool IsValid { get { return valid && (actor == null || (actor.IsInWorld && !actor.IsDead() && actor.Generation == generation)); } }
+		public bool IsValid { get { return Type != TargetType.Invalid; } }
-		public Actor Actor { get { return IsActor ? actor : null; } }
+		public Actor Actor { get { return actor; } }
 
-		// TODO: This should return true even if the actor is destroyed
+		public TargetType Type
-		public bool IsActor { get { return actor != null && !actor.Destroyed; } }
+		{
+			get
+			{
+				if (type == TargetType.Actor)
+				{
+					// Actor is no longer in the world
+					if (!actor.IsInWorld || actor.IsDead())
+						return TargetType.Invalid;
+
+					// Actor generation has changed (teleported or captured)
+					if (actor.Generation != generation)
+						return TargetType.Invalid;
+				}
+
+				return type;
+			}
+		}
 
 		// Representative position - see Positions for the full set of targetable positions.
 		public WPos CenterPosition
 		{
 			get
 			{
-				if (!IsValid)
+				if (Type == TargetType.Invalid)
 					throw new InvalidOperationException("Attempting to query the position of an invalid Target");
 
 				return actor != null ? actor.CenterPosition : pos;
@@ -67,7 +84,7 @@ namespace OpenRA.Traits
 		{
 			get
 			{
-				if (!IsValid)
+				if (Type == TargetType.Invalid)
 					return NoPositions;
 
 				if (actor == null)
@@ -83,7 +100,7 @@ namespace OpenRA.Traits
 
 		public bool IsInRange(WPos origin, WRange range)
 		{
-			if (!IsValid)
+			if (Type == TargetType.Invalid)
 				return false;
 
 			// Target ranges are calculated in 2D, so ignore height differences

OpenRA.Game/Traits/Util.cs

@@ -134,7 +134,7 @@ namespace OpenRA.Traits
 
 		public static IEnumerable<CPos> AdjacentCells(Target target)
 		{
-			var cells = target.IsActor
+			var cells = target.Type == TargetType.Actor
 				? target.Actor.OccupiesSpace.OccupiedCells().Select(c => c.First).ToArray()
 				: new CPos[] { };
 

OpenRA.Mods.RA/Activities/Attack.cs

@@ -33,7 +33,7 @@ namespace OpenRA.Mods.RA.Activities
 		public Attack(Target target, WRange range, bool allowMovement)
 		{
 			Target = target;
-			if (target.IsActor)
+			if (target.Type == TargetType.Actor)
 				targetable = target.Actor.TraitOrDefault<ITargetable>();
 
 			Range = range;

OpenRA.Mods.RA/Activities/CaptureActor.cs

@@ -24,7 +24,7 @@ namespace OpenRA.Mods.RA.Activities
 
 		public override Activity Tick(Actor self)
 		{
-			if (!target.IsValid)
+			if (target.Type != TargetType.Actor)
 				return NextActivity;
 
 			var capturable = target.Actor.Trait<Capturable>();

OpenRA.Mods.RA/Activities/Demolish.cs

@@ -27,13 +27,13 @@ namespace OpenRA.Mods.RA.Activities
 
 		public override Activity Tick(Actor self)
 		{
-			if (IsCanceled || !target.IsValid)
+			if (IsCanceled || target.Type != TargetType.Actor)
 				return NextActivity;
 
 			self.World.AddFrameEndTask(w => w.Add(new DelayedAction(delay, () =>
 			{
 				// Can't demolish an already dead actor
-				if (!target.IsValid)
+				if (target.Type != TargetType.Actor)
 					return;
 
 				// Invulnerable actors can't be demolished

OpenRA.Mods.RA/Activities/DonateSupplies.cs

@@ -27,7 +27,7 @@ namespace OpenRA.Mods.RA.Activities
 
 		public override Activity Tick(Actor self)
 		{
-			if (IsCanceled || !target.IsValid || !target.IsActor)
+			if (IsCanceled || target.Type != TargetType.Actor)
 				return NextActivity;
 
 			var targetActor = target.Actor;

OpenRA.Mods.RA/Activities/Enter.cs

@@ -27,7 +27,7 @@ namespace OpenRA.Mods.RA.Activities
 
 		public override Activity Tick(Actor self)
 		{
-			if (IsCanceled || !target.IsValid)
+			if (IsCanceled || target.Type != TargetType.Actor)
 				return NextActivity;
 
 			if (!Util.AdjacentCells(target).Any(c => c == self.Location))

OpenRA.Mods.RA/Activities/Heal.cs

@@ -22,7 +22,7 @@ namespace OpenRA.Mods.RA.Activities
 
 		protected override Activity InnerTick(Actor self, AttackBase attack)
 		{
-			if (Target.IsActor && Target.Actor.GetDamageState() == DamageState.Undamaged)
+			if (Target.Type == TargetType.Actor && Target.Actor.GetDamageState() == DamageState.Undamaged)
 				return NextActivity;
 
 			return base.InnerTick(self, attack);

OpenRA.Mods.RA/Activities/Infiltrate.cs

@@ -21,7 +21,7 @@ namespace OpenRA.Mods.RA.Activities
 
 		public override Activity Tick(Actor self)
 		{
-			if (IsCanceled || !target.IsValid || target.Actor.Owner == self.Owner)
+			if (IsCanceled || target.Type != TargetType.Actor || target.Actor.Owner == self.Owner)
 				return NextActivity;
 
 			foreach (var t in target.Actor.TraitsImplementing<IAcceptInfiltrator>())

OpenRA.Mods.RA/Activities/LegacyCaptureActor.cs

@@ -23,9 +23,7 @@ namespace OpenRA.Mods.RA.Activities
 
 		public override Activity Tick(Actor self)
 		{
-			if (IsCanceled)
+			if (IsCanceled || target.Type != TargetType.Actor)
-				return NextActivity;
-			if (!target.IsValid)
 				return NextActivity;
 
 			var b = target.Actor.TraitOrDefault<Building>();

OpenRA.Mods.RA/Activities/RepairBridge.cs

@@ -21,7 +21,7 @@ namespace OpenRA.Mods.RA.Activities
 
 		public override Activity Tick(Actor self)
 		{
-			if (IsCanceled || !target.IsValid)
+			if (IsCanceled || target.Type != TargetType.Actor)
 				return NextActivity;
 
 			var hut = target.Actor.Trait<BridgeHut>();

OpenRA.Mods.RA/Activities/RepairBuilding.cs

@@ -21,7 +21,7 @@ namespace OpenRA.Mods.RA.Activities
 
 		public override Activity Tick(Actor self)
 		{
-			if (IsCanceled || !target.IsValid)
+			if (IsCanceled || target.Type != TargetType.Actor)
 				return NextActivity;
 
 			var health = target.Actor.Trait<Health>();

OpenRA.Mods.RA/Attack/AttackBase.cs

@@ -54,7 +54,7 @@ namespace OpenRA.Mods.RA
 			if (self.IsDisabled())
 				return false;
 
-			if (target.IsActor && target.Actor.HasTrait<ITargetable>() &&
+			if (target.Type == TargetType.Actor && target.Actor.HasTrait<ITargetable>() &&
 				!target.Actor.Trait<ITargetable>().TargetableBy(target.Actor,self))
 				return false;
 
@@ -114,7 +114,7 @@ namespace OpenRA.Mods.RA
 		{
 			if (order is AttackOrderTargeter)
 			{
-				if (target.IsActor)
+				if (target.Type == TargetType.Actor)
 					return new Order("Attack", self, queued) { TargetActor = target.Actor };
 				else
 					return new Order("Attack", self, queued) { TargetLocation = target.CenterPosition.ToCPos() };

OpenRA.Mods.RA/Attack/AttackLeap.cs

@@ -37,7 +37,7 @@ namespace OpenRA.Mods.RA
 
 		public override void DoAttack(Actor self, Target target)
 		{
-			if (!CanAttack(self, target) || !target.IsActor)
+			if (target.Type != TargetType.Actor || !CanAttack(self, target))
 				return;
 
 			var a = ChooseArmamentForTarget(target);

OpenRA.Mods.RA/Attack/AttackTurreted.cs

@@ -67,7 +67,7 @@ namespace OpenRA.Mods.RA
 			base.ResolveOrder(self, order);
 
 			if (order.OrderString == "Stop")
-				target = Target.None;
+				target = Target.Invalid;
 		}
 
 		public virtual void BuildingComplete(Actor self) { buildComplete = true; }

OpenRA.Mods.RA/Move/Move.cs

@@ -258,7 +258,7 @@ namespace OpenRA.Mods.RA.Move
 				return Enumerable.Reverse(path).Select(c => Target.FromCell(c));
 			if (destination != null)
 				return new Target[] { Target.FromCell(destination.Value) };
-			return Target.NoTargets;
+			return Target.None;
 		}
 
 		abstract class MovePart : Activity