A complete first-class description of datatypes?

Gabriel, I'm wondering if you're aware of any first-class description of datatypes. I don't mean the encoding themselves, but an actual representation of the types per see. For example, the description of `Bool` would somehow encode the information in `data Bool = True | False` and, with it, one could create both constructors generically. The description of `List` would be a function `Description -> Description`, which could, again, be used to create the `cons Type` and `nil Type` constructors. I guess you get what I'm talking about. Is there any reference for that?