data (f :+: g) h e

caseH

type family Elem f g :: Emb

type family Choose e1 r :: Emb

type family Sum' e1 r :: Emb

data Proxy a

class Subsume e f g

type f :<: g

inj

proj

type f :=: g

spl

data (f :*: g) a

fst

snd

data (f :&: a) g e

class DistAnn s p s'

class RemA s s'