[GHC] #11276: GHC hangs/takes an exponential amount of time with simple program

[GHC]

#11276: GHC hangs/takes an exponential amount of time with simple program
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        Reporter:  mpickering        |                Owner:  gkaracha
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by gkaracha):

 Replying to [ticket:11276 mpickering]:
 > This was discovered when trying to compile xml-conduit. Here is the
 standalone test case with a few comments indicating how to make it
 compile.
 >
 > The program compiles with ghc-7.10.2 but fails with HEAD.
 >
 > {{{#!hs
 > -- Add this and it works
 > --    dropWS :: Monad m => ConduitM Event o m (Maybe Event)
 > }}}

 Thanks for the comments! If you just add the signature it really does
 compile? This is a bit strange, since the check runs post-typechecking
 so I would expect to have the same signature inferred at this point so
 I would not expect it to make a difference. I'll have to take a closer
 look, thanks :)

 George

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11276#comment:4>
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