predTypeEqRel :: PredType -> EqRel
predTypeEqRel ty
  | Just (tc, _) <- splitTyConApp_maybe ty
  , tc `hasKey` coercibleTyConKey
  = ReprEq
  | otherwise
  = NomEq
predTypeEqRel :: PredType -> EqRel
predTypeEqRel ty
  | Just (tc, _) <- splitTyConApp_maybe ty
  , tc `hasKey` coercibleTyConKey
  = ReprEq
  | otherwise
  = NomEq
predTypeEqRel ty
  | Just (tc, _) <- splitTyConApp_maybe ty
  , tc `hasKey` coercibleTyConKey
  = ReprEq
  | otherwise
  = NomEq