haskell - 有没有办法使用 Template Haskell 枚举模块中的所有函数？

Question

虽然我可以使用 reify 要获取有关大多数其他句法结构的信息，我找不到任何可以提供有关模块的信息的东西。

Answer 1

不幸的是，Haskell 模板目前没有这样的能力。所有解决方案都涉及解析模块的源代码。然而 location和 loc_filename TH 的功能可以很容易地找到带有调用接头的模块。

这是从 the source code 中提取的解决方案我的一个项目:

{-# LANGUAGE LambdaCase, TupleSections #-}
import Language.Haskell.TH
import qualified Data.Attoparsec.Text as AP
import qualified Data.Text.IO as Text
import qualified Data.Text as Text
import qualified Data.Char as Char
import Data.Maybe
import Data.List
import Control.Applicative
import Data.Traversable
import Prelude hiding (mapM)


reifyLocalFunctions :: Q [(Name, Type)]
reifyLocalFunctions =
  listTopLevelFunctionLikeNames >>=
  mapM (\name -> reifyFunction name >>= mapM (return . (name, ))) >>=
  return . catMaybes
  where
    listTopLevelFunctionLikeNames = do 
      loc <- location
      text <- runIO $ Text.readFile $ loc_filename loc
      return $ map (mkName . Text.unpack) $ nub $ parse text
      where
        parse text = 
          either (error . ("Local function name parsing failure: " ++)) id $
          AP.parseOnly parser text
          where
            parser = 
              AP.sepBy (optional topLevelFunctionP <* AP.skipWhile (not . AP.isEndOfLine)) 
                       AP.endOfLine >>=
              return . catMaybes
              where
                topLevelFunctionP = do
                  head <- AP.satisfy Char.isLower
                  tail <- many (AP.satisfy (\c -> Char.isAlphaNum c || c `elem` ['_', '\'']))
                  return $ Text.pack $ head : tail

reifyFunction :: Name -> Q (Maybe Type)
reifyFunction name = do
  tryToReify name >>= \case
    Just (VarI _ t _ _) -> return $ Just $ t
    _ -> return Nothing

tryToReify :: Name -> Q (Maybe Info)
tryToReify n = recover (return Nothing) (fmap Just $ reify n)