labels.hs

{-# LANGUAGE OverloadedLabels #-}
{-# LANGUAGE UndecidableInstances #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE DataKinds #-}

import Control.Monad.IO.Class
import Data.Proxy
import GHC.Exts
import GHC.OverloadedLabels (IsLabel(..))
import GHC.TypeLits
import System.Process.Typed

instance (MonadIO m,
          str ~ String,
          ret ~ ([str] -> m ExitCode),
          KnownSymbol cmd)
       => IsLabel cmd ret where
  fromLabel = \args ->
    runProcess (proc (symbolVal (Proxy :: Proxy cmd)) args)