[GHC] #9001: unexpected runtime crash

[GHC]

#9001: unexpected runtime crash
-------------------------------------+------------------------------------
        Reporter:  jwlato            |            Owner:  simonmar
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Runtime System    |          Version:  7.8.2
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  Runtime crash     |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
-------------------------------------+------------------------------------

Comment (by monoidal):

 I've reduced the testcase, but it got messy; compiling `ghc-7.8.2 X.hs`
 and running should give an internal error:

 {{{
 {-# LANGUAGE RankNTypes #-}

 newtype FMList = FM {unFM :: forall m. (m -> m -> m) -> m -> m}

 main = print $ build $ delete $ FM (\_ x -> x)

 delete l = FM (\map x -> unFM l const (const undefined) `seq` unFM (delete
 (dr l)) map x `seq` x)

 build t = unFM t (.) (+1) 0

 dr t = FM $ \_ g -> unFM t (.) (const g) undefined
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9001#comment:4>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler