[GHC] #11550: ghc-HEAD -DDEBUG is broken (possiby by D1880)

[GHC]

#11550: ghc-HEAD -DDEBUG is broken (possiby by D1880)
-------------------------------------+-------------------------------------
           Reporter:  slyfox         |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Compile-time
  Unknown/Multiple                   |  crash
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 Was found when tried to build with
     BuildFlavour = devel2

 {{{
 ghc-validate $ LANG=C make V=0

   HC [stage 2] libraries/parallel/dist-install/build/Control/Seq.o
 WARNING: file compiler/stgSyn/CoreToStg.hs, line 250
   using False True
 ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 8.1.20160206 for x86_64-unknown-linux):
         ASSERT failed!
   CallStack (from HasCallStack):
   assertPprPanic, called at compiler/stgSyn/CoreToStg.hs:216:59 in
 ghc:CoreToStg
   using

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

 }}}

     https://travis-ci.org/ghc/ghc/builds
 suggests
     changeset:4f9967aa3d1f7cfd539d0c173cafac0fe290e26f
 might be at fault.

 Reverting it on top of master fixes devel2 build.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11550>
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