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ghc: panic! (the 'impossible' happened)

    • Closed Issue created by mcapodici @trac-mcapodici
    • *When I build my program I get this:**
    play-0.1.0.0: build (exe)
Preprocessing executable 'play' for play-0.1.0.0...
[1 of 1] Compiling Main             ( src/Main.hs, .stack-work/dist/x86_64-linux-nopie/Cabal-1.24.2.0/build/play/play-tmp/Main.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 8.0.2 for x86_64-unknown-linux):
	initTc: unsolved constraints
  WC {wc_insol =
        [W] interactD_aL2 :: t_aL1[tau:1] (CHoleCan: interactD)
        [W] interactD_aLt :: t_aLs[tau:1] (CHoleCan: interactD)}

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
    • *The code:**
    {-# LANGUAGE GADTs #-}

module Main where

import Control.Monad.Trans.Cont
import Control.Monad.Trans.Class

--main :: IO ()

{-- CONTT --
main = evalContT contt

contt :: ContT () IO ()
contt = do
    k <- do
      callCC $ \exit -> do
        lift $ putStrLn "Entry"
        exit $ \_ -> do
          putStrLn "Exit"
    lift $ putStrLn "Inside"
    lift $ k ()
    
--}
{--
class Monad m => Interact m where
  get :: m String
  say :: String -> m ()

instance Interact IO where
  get = getLine
  say = putStrLn

prog :: Interact a => a ()
prog = do 
  say "Hello what is your name?"
  name <- get
  say $ "Hello " ++ name ++ ", I am prog! Goodbye"

main :: IO ()
main = prog
--}


data InteractD m = InteractD 
  { getD :: m String
  , sayD :: String -> m () 
  }

interactDIO :: InteractD IO
interactDIO = interactD getLine putStrLn

interactDIO2 :: InteractD IO
interactDIO2 = interactD (return "James") putStrLn
    Trac metadata
    Trac field Value
    Version 8.0.2
    Type Bug
    TypeOfFailure OtherFailure
    Priority normal
    Resolution Unresolved
    Component Compiler
    Test case
    Differential revisions
    BlockedBy
    Related
    Blocking
    CC
    Operating system
    Architecture
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