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{-# LANGUAGE DeriveDataTypeable #-}
import Control.Exception as E
import Data.Typeable
throwIfNegative :: Int -> String
throwIfNegative n | n < 0 = error "negative"
| otherwise = "no worries"
{-# NOINLINE throwIfNegative #-}
data HUnitFailure = HUnitFailure String deriving (Show,Typeable)
instance Exception HUnitFailure
assertFailure :: String -> a -- Not an IO function!
assertFailure msg = E.throw (HUnitFailure msg)
main :: IO ()
main =
handleJust errorCalls (const (return ())) (do
evaluate (throwIfNegative (-1)) -- Pure expression evaluated in IO
assertFailure "must throw when given a negative number")
where errorCalls (ErrorCall _) = Just ()
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