type-name.hs

module Main (main) where

import Control.Monad (when)
import Data.Proxy (Proxy (..))
import Data.String (IsString (..))
import Data.Void (Void)
import Type.Reflection

typeName
  :: forall a s proxy
   . (Typeable a, IsString s)
  => proxy a -> s
typeName _ =
  fromString . tyConName . typeRepTyCon $ TypeRep @a

main :: IO ()
main = do
  let typeNames =
        [ (typeName (Proxy @()), "()")
        , (typeName (Proxy @Void), "Void")
        , (typeName (Proxy @Bool), "Bool")
        , (typeName (Proxy @(Proxy ())), "Proxy")
        , (typeName (Proxy @(Maybe ())), "Maybe")
        ]
  
  print typeNames

  let itWorks = and $ do
        (actual, expected) <- typeNames
        pure $ expected == actual

  when itWorks $ putStrLn "It works!"