data kinds

GHC implements data kinds by promoting data declarations of a certain restricted form, but I wonder if it would be better to have a special syntax for kind definitions, say data kind Nat = Zero | Succ Nat At the moment, things get promoted whether you need them or not, and if you've made some mistake that makes your definition non-promotable you don't find out until you try to use it. More importantly, a separate form for kinds would allow one to use existing kinds, i.e. *, in definitions of new kinds.