This should throw an exception

module Main where

import Control.Concurrent.STM
import Control.Concurrent
import Control.Monad
import Text.Show

main :: IO ()
main = do
  foo <- newTVarIO 1
  forkIO $ do
    forever $ do
      atomically $ do
        writeTVar foo 0
        writeTVar foo 1
  forkIO $ do
    forever $ do
      bar <- atomically $ do
        bar <- readTVar foo
        return $ 1 `div` bar
      putStrLn $ show bar
  forever $ do
    putStrLn "foo"