:set -XTemplateHaskell
import Language.Haskell.TH
let seeType n = do VarI _ t _ <- reify n; runIO $ putStrLn $ show t; [| return True |]
let f :: Int -> Int; f = undefined
let g :: [Int]     ; g = undefined
let h :: (Int, Int); h = undefined
$(seeType (mkName "f"))
$(seeType (mkName "g"))
$(seeType (mkName "h"))