A mix of Vinyl style and SOP style

gistfile1.hs

foldRRec :: forall f xs c a b p.
            RecAll f xs c 
         => p c
         -> (forall x. c x => x -> a) 
         -> (a -> b -> b) 
         -> b 
         -> NP f xs
         -> b
foldRRec p convert f z xs 
  = foldRRec' convert f z 
  $ reifyConstraint p xs

foldRRec' :: RecAll f xs c 
          =>  (forall x. c x => x -> a) 
          -> (a -> b -> b) 
          -> b 
          -> NP (Dict c :. f) xs
          -> b
foldRRec' _ _ z Nil = z
foldRRec' convert f z ((Compose (Dict x)) :* xs) 
  = f (convert x) 
  $ foldRRec' convert f z xs

reifyConstraint
  :: RecAll f rs c
  => proxy c
  -> NP f rs
  -> NP (Dict c :. f) rs
reifyConstraint prx rec =
  case rec of
    Nil -> Nil
    (x :* xs) -> Compose (Dict x) :* reifyConstraint prx xs
    
foldMapG :: forall f xs c m p.
            (RecAll f xs c, Monoid m)
         => p c
         -> (forall x. c x => x -> m)
         -> NP f xs 
         -> m
foldMapG p f xs = foldRRec p f (<>) mempty xs