Propositional equality for Datatype meta-information
Make constructor metadata parametrized (with intended parameter <- datatype)
Implement sameConstructor
get roles right and fix a FIXME
Actually parametrize the Constructor with the Datatype
Supply a reasonable name (should be derived from d_name tho)
Use 'd_name' as the name (should be derived from d_name tho)
Add default case (fixes -Werror)