Data Convert Function using Template Haskell

Convert.hs

{-# LANGUAGE TemplateHaskell #-}

import Language.Haskell.TH
import Control.Applicative ((<$>))

data Hoge = Hoge1 | Hoge2 | Hoge3 deriving (Eq, Show)
data Fuga = Fuga1 | Fuga2 deriving (Eq, Show)

-- runQ [| \t -> case t of "hoge1" -> Hoge1; "hoge2" -> Hoge2; "hoge3" -> Hoge3; _ -> error "Hoge" |]

convertHogeTH :: ExpQ
convertHogeTH = do
  t_0 <- newName "t"
  return $ LamE [VarP t_0]
    (CaseE (VarE t_0)
      [ Match (LitP (StringL "hoge1")) (NormalB (ConE 'Hoge1)) []
      , Match (LitP (StringL "hoge2")) (NormalB (ConE 'Hoge2)) []
      , Match (LitP (StringL "hoge3")) (NormalB (ConE 'Hoge3)) []
      , Match WildP (NormalB (AppE (VarE 'error) (LitE (StringL "Hoge")))) []
      ]
    )

mkConvertFunc' :: Name -> [(String, Name)] -> ExpQ
mkConvertFunc' d lst = do
  t_0 <- newName "t"
  return $ LamE [VarP t_0]
    (CaseE (VarE t_0)
      $ (map (\(s, t) -> Match (LitP (StringL s)) (NormalB (ConE t)) []) lst)
      ++ [Match WildP (NormalB (AppE (VarE 'error) (LitE (StringL $ show d)))) []])

$(do
   info <- reify ''Hoge
   runIO $ print info
   return [])

$(do
  ctrs <- (\(TyConI (DataD [] _ [] x [])) -> map (\(NormalC name []) -> name) x)
          <$> reify ''Hoge
  runIO $ print $ ctrs
  return [])

mkConvertFunc :: Name -> [String] -> ExpQ
mkConvertFunc d strs = do
  ctrs <- (\(TyConI (DataD [] _ [] x [])) -> map (\(NormalC name []) -> name) x)
          <$> reify d
  v <- newName "x"
  return $ LamE [VarP v]
    (CaseE (VarE v)
       $ (map (\(s,t) -> Match (LitP (StringL s)) (NormalB (ConE t)) []) $ zip strs ctrs)
       ++ [Match WildP (NormalB (AppE (VarE 'error) (LitE (StringL $ show d)))) []])