[Haskell-cafe] Type-level lazy bool operations

Hello, cafe! There are some type-level boolean operation (If, &&, ||, Not) in Data.Type.Bool. Are they lazy enough? I faced with problem and it seems that the reason is non-lazy "If". I.e. both (on-True and on-False) types are trying to be calculated. Does it work in this way really? Could it be changed? Then, looking into source I see such definition for (&&) -- | Type-level "and" type family a && b where 'False && a = 'False 'True && a = a a && 'False = 'False a && 'True = a a && a = a Why we need the last three rules? Does it mean that an order of type calculation is totaly undefined? Dmitry