Final call for GHC String Interpolation proposal!

I think there need to be more Show like classes, for pretty printing and user facing. For example Pretty would ensure readable lists, while UserFacing printing for Data.Map.Map would not include a fromList. The UserFacing class seems to be called Interpolate by you, but it is a separate issue, and could be implemented without any GHC extensions. I think adding those classes would be a good first step.