Test.hs

-- |Testing `Alternative` instance behavior via (<|>)
-- in conjunction with Exceptions.
--
-- Behavior is not consistent.
module Test where

import Control.Applicative
import Control.Monad.Catch
import Data.Typeable


test1 :: IO ()
test1 = (fail "") <|> print "abc"

test2 :: IO ()
test2 = (throwM $ userError "") <|> print "abc"


data MyException = MkException String
  deriving (Show, Eq, Typeable)

instance Exception MyException


test3 :: IO ()
test3 = (throwM $ MkException "") <|> print "abc"



{--
running:

*Test> test1
"abc"
*Test> test2
"abc"
*Test> test3
*** Exception: MkException ""


types:

*Test> :t fail ""
fail "" :: Monad m => m a
*Test> :t throwM $ userError ""
throwM $ userError "" :: MonadThrow m => m a
*Test> :t throwM $ MkException ""
throwM $ MkException "" :: MonadThrow m => m a

--}