[GHC] #12760: Assertion failed with BuildFlavour = devel2 (yet another)

[GHC]

#12760: Assertion failed with BuildFlavour = devel2 (yet another)
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        Reporter:  pacak             |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 > ghc needs to be compiled with BuildVlavour = devel2

 Which exact version of GHC are you building?   Can you try with the
 `ghc-8.0` branch?  I don't get this assertion failure when compiling the
 module you give above; and it might well have been fixed.

 Is this a show-stopper for you?  This particular assertion failure is
 almost certainly not a problem; we should fix it (that's why it's there)
 but it probably won't cause any problems.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12760#comment:1>
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