Having some fun (and pain) with generics

Decided to try and wrap my head around generic programming and ended up sinking too much time trying to understand (or not?) some of the basic ideas. Just for fun, I tried to think how it would be possible to go from a homogenous list back to possibly a data structure.

module Foo where

import           Data.Maybe
import           Generics.SOP
import           Generics.SOP.TH

data Foo = F String Int
  deriving (Eq, Show)

deriveGeneric ''Foo

homoLstToFoo :: [String] -> Maybe Foo
homoLstToFoo xs
  = case iterP homoP of
      Nothing -> Nothing
      Just ps -> Just $ (to . SOP . Z) ps
  where
    homoP :: xs ~ [String, String] => Maybe (NP (K String) xs)
    homoP = fromList xs

    iterP :: Maybe (NP (K String) xs) -> Maybe (NP I '[String, Int])
    iterP mLst = case mLst of
      Nothing -> Nothing
      Just (x :* y :* _) -> case readMay (unK y) :: Maybe Int of
        Just z -> Just $ I (unK x :: String) :* I z :* Nil
        Nothing -> Nothing