Resolving dependencies...
Configuring generics-mrsop-1.2.2...
Building generics-mrsop-1.2.2...
Failed to install generics-mrsop-1.2.2
Build log ( /home/builder/.cabal/logs/ghc-8.4.3/generics-mrsop-1.2.2-6U4k1uomQBtFAFG52l2lbI.log ):
cabal: Entering directory '/tmp/cabal-tmp-18296/generics-mrsop-1.2.2'
Configuring generics-mrsop-1.2.2...
Preprocessing library for generics-mrsop-1.2.2..
Building library for generics-mrsop-1.2.2..
[ 1 of 18] Compiling Generics.MRSOP.Util ( src/Generics/MRSOP/Util.hs, dist/build/Generics/MRSOP/Util.o )
[ 2 of 18] Compiling Generics.MRSOP.Opaque ( src/Generics/MRSOP/Opaque.hs, dist/build/Generics/MRSOP/Opaque.o )
[ 3 of 18] Compiling Generics.MRSOP.Base.NS ( src/Generics/MRSOP/Base/NS.hs, dist/build/Generics/MRSOP/Base/NS.o )
[ 4 of 18] Compiling Generics.MRSOP.Base.NP ( src/Generics/MRSOP/Base/NP.hs, dist/build/Generics/MRSOP/Base/NP.o )
[ 5 of 18] Compiling Generics.MRSOP.Base.Universe ( src/Generics/MRSOP/Base/Universe.hs, dist/build/Generics/MRSOP/Base/Universe.o )
[ 6 of 18] Compiling Generics.MRSOP.Base.Show ( src/Generics/MRSOP/Base/Show.hs, dist/build/Generics/MRSOP/Base/Show.o )
[ 7 of 18] Compiling Generics.MRSOP.Base.Class ( src/Generics/MRSOP/Base/Class.hs, dist/build/Generics/MRSOP/Base/Class.o )
[ 8 of 18] Compiling Generics.MRSOP.Base.Metadata ( src/Generics/MRSOP/Base/Metadata.hs, dist/build/Generics/MRSOP/Base/Metadata.o )
[ 9 of 18] Compiling Generics.MRSOP.TH ( src/Generics/MRSOP/TH.hs, dist/build/Generics/MRSOP/TH.o )
[10 of 18] Compiling Generics.MRSOP.Base.Combinators ( src/Generics/MRSOP/Base/Combinators.hs, dist/build/Generics/MRSOP/Base/Combinators.o )
[11 of 18] Compiling Generics.MRSOP.Base ( src/Generics/MRSOP/Base.hs, dist/build/Generics/MRSOP/Base.o )
[12 of 18] Compiling Generics.MRSOP.Examples.RoseTreeTH ( src/Generics/MRSOP/Examples/RoseTreeTH.hs, dist/build/Generics/MRSOP/Examples/RoseTreeTH.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 8.4.3 for x86_64-unknown-linux):
	completeCall
  fail_avwV
  Select nodup wild_00
  Stop[BoringCtxt] Rep
                     Singl (El FamRoseInt) (Lkup ix_avAt CodesRoseInt)
  Call stack:
      CallStack (from HasCallStack):
        callStackDoc, called at compiler/utils/Outputable.hs:1150:37 in ghc:Outputable
        pprPanic, called at compiler/simplCore/Simplify.hs:1533:9 in ghc:Simplify

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

cabal: Leaving directory '/tmp/cabal-tmp-18296/generics-mrsop-1.2.2'
cabal: Error: some packages failed to install:
generics-mrsop-1.2.2-6U4k1uomQBtFAFG52l2lbI failed during the building phase.
The exception was:
ExitFailure 1