k vs *

insert
  :: (KnownSymbol k, Typeable i, ChannelType k api ~ i)
  => Proxy api -> Proxy k -> f i -> RouteMap f routes -> RouteMap f ((k :> i) ': routes)
insert _ pKey i = Routes . Map.insert k (I i) . unRoutes
  where
    k = (symbolVal pKey) ^. packed


type family Chan (chan :: *) :: * where
  Chan (chan :> a) = a
--------------------------------------------------------------------------------
class Channels api where
  type Chans api :: [*]
  mkChannels :: Proxy api -> IO (RouteMap Input (Chans api), RouteMap Output (Chans api))

instance (KnownSymbol chan, Typeable a, Chan a ~ ty) => Channels (chan :> a) where
  type Chans (chan :> a) = '[chan :> (Chan (chan :> a))]
  mkChannels pApi = do
    (o :: Output a, i :: Input a) <- spawn unbounded
    let inp = insert pApi pK i emptyRoutes -- :: RouteMap Input '[chan :> a]
        out = insert pApi pK o emptyRoutes
    return (inp, out) -- insert pApi pK o emptyRoutes
    where pK = Proxy :: Proxy chan