Check ITargetable when deciding target validity. Fixes #3659.

OpenRA.Game/Orders/UnitOrderGenerator.cs

@@ -99,7 +99,7 @@ namespace OpenRA.Orders
 			if (self.Owner != self.World.LocalPlayer)
 				return null;
 
-			if (self.Destroyed || target.Type == TargetType.Invalid)
+			if (self.Destroyed || !target.IsValidFor(self))
 				return null;
 
 			if (mi.Button == Game.mouseButtonPreference.Action)

OpenRA.Game/Traits/DrawLineToTarget.cs

@@ -64,7 +64,7 @@ namespace OpenRA.Traits
 
 			foreach (var target in targets)
 			{
-				if (!target.IsValid)
+				if (target.Type == TargetType.Invalid)
 					continue;
 
 				var to = wr.ScreenPxPosition(target.CenterPosition);

OpenRA.Game/Traits/Selectable.cs

@@ -161,7 +161,7 @@ namespace OpenRA.Traits
 				var c = Color.Green;
 
 				var wlr = Game.Renderer.WorldLineRenderer;
-				foreach (var stp in targets.Where(t => t.IsValid).Select(p => wr.ScreenPxPosition(p.CenterPosition)))
+				foreach (var stp in targets.Where(t => t.Type != TargetType.Invalid).Select(p => wr.ScreenPxPosition(p.CenterPosition)))
 				{
 					wlr.DrawLine(stp + new float2(-1, -1), stp + new float2(-1, 1), c, c);
 					wlr.DrawLine(stp + new float2(-1, 1), stp + new float2(1, 1), c, c);

OpenRA.Game/Traits/Target.cs

@@ -22,6 +22,7 @@ namespace OpenRA.Traits
 
 		TargetType type;
 		Actor actor;
+		ITargetable targetable;
 		FrozenActor frozen;
 		WPos pos;
 		int generation;
@@ -40,6 +41,7 @@ namespace OpenRA.Traits
 			return new Target
 			{
 				actor = a,
+				targetable = a != null ? a.TraitOrDefault<ITargetable>() : null,
 				type = a != null ? TargetType.Actor : TargetType.Invalid,
 				generation = a.Generation,
 			};
@@ -47,7 +49,6 @@ namespace OpenRA.Traits
 
 		public static Target FromFrozenActor(FrozenActor a)  { return new Target { frozen = a, type = TargetType.FrozenActor }; }
 
-		public bool IsValid { get { return Type != TargetType.Invalid; } }
 		public Actor Actor { get { return actor; } }
 		public FrozenActor FrozenActor { get { return frozen; } }
 
@@ -70,6 +71,17 @@ namespace OpenRA.Traits
 			}
 		}
 
+		public bool IsValidFor(Actor targeter)
+		{
+			if (Type == TargetType.Invalid)
+				return false;
+
+			if (targetable != null && !targetable.TargetableBy(actor, targeter))
+				return false;
+
+			return true;
+		}
+
 		// Representative position - see Positions for the full set of targetable positions.
 		public WPos CenterPosition
 		{