Replace arrays with sets.

In places where arrays were being treated as a set, just create a set directly. This reveals the intention of such collections better, and also improves performance by allowing set based methods to be used.

OpenRA.Game/Traits/Player/FrozenActorLayer.cs

@@ -27,7 +27,7 @@ namespace OpenRA.Traits
 		public readonly PPos[] Footprint;
 		public readonly WPos CenterPosition;
 		public readonly Rectangle Bounds;
-		public readonly string[] TargetTypes;
+		public readonly HashSet<string> TargetTypes;
 		readonly IRemoveFrozenActor[] removeFrozenActors;
 		readonly Actor actor;
 		readonly Shroud shroud;
@@ -57,7 +57,7 @@ namespace OpenRA.Traits
 
 			CenterPosition = self.CenterPosition;
 			Bounds = self.Bounds;
-			TargetTypes = self.TraitsImplementing<ITargetable>().Where(Exts.IsTraitEnabled).SelectMany(t => t.TargetTypes).Distinct().ToArray();
+			TargetTypes = self.TraitsImplementing<ITargetable>().Where(Exts.IsTraitEnabled).SelectMany(t => t.TargetTypes).ToHashSet();
 
 			UpdateVisibility();
 		}

OpenRA.Game/Traits/TraitsInterfaces.cs

@@ -310,13 +310,13 @@ namespace OpenRA.Traits
 
 	public interface ITargetableInfo
 	{
-		string[] GetTargetTypes();
+		HashSet<string> GetTargetTypes();
 	}
 
 	public interface ITargetable
 	{
 		// Check IsTraitEnabled or !IsTraitDisabled first
-		string[] TargetTypes { get; }
+		HashSet<string> TargetTypes { get; }
 		bool TargetableBy(Actor self, Actor byActor);
 		bool RequiresForceFire { get; }
 	}