pretty-show fails to build on appveyor

[simonmichael]

My appveyor logs include this:

pretty-show-1.7: configure
pretty-show-1.7: build
--  While building custom Setup.hs for package pretty-show-1.7 using:
      C:\sr\setup-exe-cache\i386-windows\Cabal-simple_Z6RU0evB_2.2.0.1_ghc-8.4.2.exe --builddir=.stack-work\dist\ba067387 build --ghc-options " -ddump-hi -ddump-to-file"
    Process exited with code: ExitFailure (-1073741819)
    Logs have been written to: C:\pr\.stack-work\logs\pretty-show-1.7.log
    Configuring pretty-show-1.7...
    Preprocessing library for pretty-show-1.7..
    Building library for pretty-show-1.7..
    [1 of 6] Compiling Paths_pretty_show ( .stack-work\dist\ba067387\build\autogen\Paths_pretty_show.hs, .stack-work\dist\ba067387\build\Paths_pretty_show.o )
    [2 of 6] Compiling Text.Show.Value  ( Text\Show\Value.hs, .stack-work\dist\ba067387\build\Text\Show\Value.o )
    [3 of 6] Compiling Text.Show.PrettyVal ( Text\Show\PrettyVal.hs, .stack-work\dist\ba067387\build\Text\Show\PrettyVal.o )
    [4 of 6] Compiling Text.Show.Parser ( .stack-work\dist\ba067387\build\Text\Show\Parser.hs, .stack-work\dist\ba067387\build\Text\Show\Parser.o )
    [5 of 6] Compiling Text.Show.Html   ( Text\Show\Html.hs, .stack-work\dist\ba067387\build\Text\Show\Html.o )

    C:\Users\appveyor\AppData\Local\Temp\1\stack2904\pretty-show-1.7\Text\Show\Html.hs:106:1: warning: [-Wunused-top-binds]
        Defined but not used: `tallTuple'
        |
    106 | tallTuple els = table "tallTuple" $ map (tr . return . td) els
        | ^^^^^^^^^
    [6 of 6] Compiling Text.Show.Pretty ( Text\Show\Pretty.hs, .stack-work\dist\ba067387\build\Text\Show\Pretty.o )
Command exited with code 1

I have two theories about what this is saying:

• the Setup.lhs is failing to compile, perhaps because it's literate haskell ? (Is there any reason not to use plain .hs ?)
• the warning about tallTuple is breaking the build, because of -Wall in the cabal file ?

I'm having trouble reproducing it locally; I don't have a windows machine.

[yav]

I am closing this, as your pull request should have addressed it. Thanks!

[simonmichael]

https://ghc.haskell.org/trac/ghc/ticket/15095