Hi GHC devs, I'm working on a GHC plugin which implements a custom instance resolution mechanism: https://github.com/noughtmare/transitive-constraint-plugin Currently, I need to place instances in a specific order in a specific file to recognize them and use them in my plugin. I think my life would be a lot easier if I could put annotations on instances. I imagine a syntax like this: data MyInstanceTypes = Refl | Trans deriving Eq class f <= g where inj :: f x -> g x instance {-# ANN instance Refl #-} f <= f where inj = id instance {-# ANN instance Trans #-} forall f g h. (f <= g, g <= h) => f <= h where inj = inj @g @h . inj @f @g Using this information I should be able to find the right instances in a more reliable way. One more thing I was thinking about is to make it possible to remove these instances from the normal resolution algorithm and only allow them to be used by my plugin. Do you think this would be easy to implement and useful? Or are there other ways to achieve this? Cheers, Jaro