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import Control.Exception as E
import Control.Concurrent
import System.IO.Unsafe
-- x is killed during evaluation with an asynchronous exception, but
-- nevertheless gets overwritten with 'throw ThreadKilled' because the
-- async exception is re-thrown as a synchrnonous exception by
-- 'onException'.
main = do
let x = unsafePerformIO $
(do threadDelay 1000000; return 42)
`onException` return ()
t <- forkIO $ do evaluate x; return ()
threadDelay 1000
killThread t
print x `E.catch` \e -> putStrLn ("main caught: " ++ show (e::SomeException))
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