Bug#851373: git-annex FTBFS on armel/armhf: ghc: panic! (the 'impossible' happened)

[Adrian Bunk]

Source: ghc
Version: 8.0.1-17
Severity: serious
Control: affects -1 src:git-annex

https://buildd.debian.org/status/package.php?p=git-annex

...
[540 of 548] Compiling Assistant.WebApp.Configurators.Pairing ( Assistant/WebApp/Configurators/Pairing.hs, dist/build/git-annex/git-annex-tmp/Assistant/WebApp/Configurators/Pairing.o )
[541 of 548] Compiling Assistant.Threads.WebApp ( Assistant/Threads/WebApp.hs, dist/build/git-annex/git-annex-tmp/Assistant/Threads/WebApp.o )
[542 of 548] Compiling Assistant        ( Assistant.hs, dist/build/git-annex/git-annex-tmp/Assistant.o )
[543 of 548] Compiling Command.Watch    ( Command/Watch.hs, dist/build/git-annex/git-annex-tmp/Command/Watch.o )
[544 of 548] Compiling Command.Assistant ( Command/Assistant.hs, dist/build/git-annex/git-annex-tmp/Command/Assistant.o )
[545 of 548] Compiling Command.WebApp   ( Command/WebApp.hs, dist/build/git-annex/git-annex-tmp/Command/WebApp.o )
[546 of 548] Compiling CmdLine.GitAnnex ( CmdLine/GitAnnex.hs, dist/build/git-annex/git-annex-tmp/CmdLine/GitAnnex.o )
[547 of 548] Compiling Test             ( Test.hs, dist/build/git-annex/git-annex-tmp/Test.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 8.0.1 for arm-unknown-linux):
	expectJust cpeBody:collect_args
CallStack (from HasCallStack):
  error, called at compiler/utils/Maybes.hs:48:27 in ghc:Maybes

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

Makefile:26: recipe for target 'git-annex' failed
make[1]: *** [git-annex] Error 1
make[1]: Leaving directory '/«PKGBUILDDIR»'
dh_auto_build: make -j1 returned exit code 2
debian/rules:15: recipe for target 'build-arch' failed
make: *** [build-arch] Error 2