39 lines
1.2 KiB
Haskell
39 lines
1.2 KiB
Haskell
{-# LANGUAGE TemplateHaskell #-}
|
|
-- | This module uses scope lookup techniques to either export
|
|
-- 'lookupValueName' from @Language.Haskell.TH@, or define
|
|
-- its own 'lookupValueName', which attempts to do the
|
|
-- same job with just 'reify'. This will sometimes fail, but if it
|
|
-- succeeds it will give the answer that the real function would have
|
|
-- given.
|
|
--
|
|
-- The idea is that if you use lookupValueName from this module,
|
|
-- your client code will automatically use the best available name
|
|
-- lookup mechanism. This means that e.g. 'scopeLookup' can work
|
|
-- very well on recent GHCs and less well but still somewhat
|
|
-- usefully on older GHCs.
|
|
module NotCPP.LookupValueName (
|
|
lookupValueName
|
|
) where
|
|
|
|
import Language.Haskell.TH
|
|
|
|
import NotCPP.Utils
|
|
|
|
bestValueGuess :: String -> Q (Maybe Name)
|
|
bestValueGuess s = do
|
|
mi <- maybeReify (mkName s)
|
|
case mi of
|
|
Nothing -> no
|
|
Just i -> case i of
|
|
VarI n _ _ _ -> yes n
|
|
DataConI n _ _ _ -> yes n
|
|
_ -> err ["unexpected info:", show i]
|
|
where
|
|
no = return Nothing
|
|
yes = return . Just
|
|
err = fail . showString "NotCPP.bestValueGuess: " . unwords
|
|
|
|
$(recover [d| lookupValueName = bestValueGuess |] $ do
|
|
VarI _ _ _ _ <- reify (mkName "lookupValueName")
|
|
return [])
|