lesserVariance :: Variance -> Variance -> Bool
lesserVariance v1 v2 = case v1 of
  InVar -> True
  _ -> case v2 of
         NonVar -> True
         _ -> v1 == v2

-- | revert variance
lesserVariance :: Variance -> Variance -> Bool
lesserVariance v1 v2 = case v1 of
  InVar -> True
  _ -> case v2 of
         NonVar -> True
         _ -> v1 == v2

-- | revert variance
lesserVariance v1 v2 = case v1 of
  InVar -> True
  _ -> case v2 of
         NonVar -> True
         _ -> v1 == v2

-- | revert variance