[GHC] #8470: "Fix" spurious Unused do-bind warnings

[GHC]

#8470: "Fix" spurious Unused do-bind warnings
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        Reporter:  2piix             |            Owner:
            Type:  feature request   |           Status:  closed
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.6.3
      Resolution:  worksforme        |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Changes (by goldfire):

 * status:  new => closed
 * resolution:   => worksforme


Comment:

 I agree that no warning should be emitted for a monadic action that
 returns `()`. But, I can't seem to reproduce this behavior with 7.6.3. For
 example, when I compile

 {{{
 {-# OPTIONS_GHC -Wall #-}

 module Bug where

 getA :: IO Int
 getA = return 5

 performSideEffect :: IO ()
 performSideEffect = return ()

 someComplicatedIOAction :: IO ()
 someComplicatedIOAction = do
    a <- getA
    performSideEffect
    putStrLn . show $ a
 }}}

 I get no warnings. Is there something I'm missing here?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8470#comment:2>
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