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Error with liftIO #3

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michaelmesser opened this issue May 24, 2017 · 0 comments

michaelmesser commented May 24, 2017

f :: IO (Either () ())
f = runM $ runError $ liftIO $ putStrLn "Hello"

Couldn't match type ‘Data.Type.Equality.EqArrow (Exc ()) m0’
                 with ‘'False’
    arising from a use of ‘liftIO’
  The type variable ‘m0’ is ambiguous
In the second argument of ‘($)’, namely
    ‘liftIO $ putStrLn "Hello"’
  In the second argument of ‘($)’, namely
    ‘runError $ liftIO $ putStrLn "Hello"’
  In the expression: runM $ runError $ liftIO $ putStrLn "Hello"

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