[GHC] #13750: GHC produces incorrect coercions in hairy code

[GHC]

#13750: GHC produces incorrect coercions in hairy code
-------------------------------------+-------------------------------------
        Reporter:  dfeuer            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.2.2
       Component:  Compiler          |              Version:  8.2.1-rc2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Runtime crash     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13429            |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by kosmikus):

 I can confirm that `-fno-specialise` also works in the full example as a
 workaround (but it seems it has to be applied at each use site of one of
 the critical functions, so it's not an extremely viable workaround for a
 library).

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13750#comment:8>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler