Hi, I'm working on an open source patch, but stumbled upon the following problem: I'm introducing a type that is basically a pointer in a FFI library, pointing to an opaque type (which I'm told is common practice). -- | An opaque type encapsulating a font in C. data Font_Opaque type Font = Ptr Font_Opaque The problem is that insertion in the current code would require this to be an instance of Data and Typeable. In this case (gloss library) I've not 100% understood why that's a requirement, I've been grepping (case-insensitive) for typeOf, constr, gfold, and I've not found any obvious use. Anyway, the rough-and-ready approach for this would be to manually define instances of Data and Typeable for the opaque type - my question is: what would sensible implementations look like for such a type? Thank you, Elise