anchor.diff:  open Nu
   module EcsTests =
   
  -    type [<Struct>] Skin =
  +    type [<NoEquality; NoComparison; Struct>] Skin =
           { mutable RefCount : int
             mutable Color : Vector4 }
           interface Component with
  
positive.code:         let airshipSystem = ecs.RegisterSystem (SystemJunctioned<Airship, World> ())
  
          // define our airship system's update behavior
          let subId = ecs.Subscribe EcsEvents.Update (fun _ _ _ world ->
              for i = 0 to airshipSystem.Components.Length - 1 do
                  let comp = &airshipSystem.Components.[i]
                  comp.Transform.Value.Enabled <- i % 2 = 0
  
negative.code:         let airship = ecs.RegisterJunctioned airshipSystem.Name Unchecked.defaultof<Airship> Gen.id
  
          // invoke update behavior
          ecs.Publish EcsEvents.Update () ecs.GlobalSystem world