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{-# LANGUAGE RebindableSyntax, MultiParamTypeClasses #-}
-- #1537
module Foo where
import Prelude hiding (Monad(..))
class Bind m1 m2 m3 where
(>>=) :: m1 a -> (a -> m2 b) -> m3 b
class Return m where
return :: a -> m a
fail :: String -> m a
instance Bind Maybe [] [] where
Just x >>= f = f x
Nothing >>= f = []
instance Return [] where
return x = [x]
fail _ = []
should_compile :: [Int]
should_compile = do
a <- Just 1
[a]
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