gistfile1.txt

-- first a separate class to interpret the access/permission DSL 
class IsAccess a where
   getAccess :: Proxy a -> Id -> Bool 
   -- ^ probably something quite different here. The two main options I see generally
   -- are evaluating to some normal form (like AccessType) and not requiring Id, or 
   -- having Id and then directly evaluating to Bool
   -- If you want to be allowed to require other values depending on the type (which I
   -- think you do) you'd need an associated type synonym).

instance (IsAccess a, IsAccess b) => IsAccess (a :|| b) where
   getAccess _ id = getAccess (Proxy :: Proxy a) id || getAccess (Proxy :: Proxy b)

-- and so on for :&&, etc. `Admin` etc. need to check the internals of `Id`, unless
-- you go down the route of evaluating to some normal form.

-- We wrap in `Access` just because of overlapping instances.
instance (IsAccess a, HasServer b) => HasServer (Access a :> b) where
   type Server (a :> b) = b   
   route _ handler req respond = -- get `Id` from header and DB (like Entity Person) and do the appropriate thing