Entity is now IEquatable

src/ComponentDepot.cs

@@ -175,6 +175,7 @@ internal class ComponentDepot
 		return new Filter(this, included, excluded);
 	}
 
+	// FIXME: this dictionary should probably just store entities
 	public IEnumerable<Entity> FilterEntities(Filter filter)
 	{
 		foreach (var id in filterSignatureToEntityIDs[filter.Signature])

src/Entity.cs

@@ -1,6 +1,6 @@
 namespace MoonTools.ECS;
 
-public struct Entity
+public struct Entity : IEquatable<Entity>
 {
 	public int ID { get; }
 
@@ -8,4 +8,19 @@ public struct Entity
 	{
 		ID = id;
 	}
+
+	public override bool Equals(object? obj)
+	{
+		return obj is Entity entity && Equals(entity);
+	}
+
+	public override int GetHashCode()
+	{
+		return HashCode.Combine(ID);
+	}
+
+	public bool Equals(Entity other)
+	{
+		return ID == other.ID;
+	}
 }