[Haskell-cafe] Bug in GHC or cabal-install?

[Edward Z. Yang]

This sounds like a Cabal bug to me. A few things to try:

- Can you post a -v3 log of the second cabal install force
  reinstall somewhere?  It sounds like we are incorrectly
  attempting to use the wrong version of Cabal to build the
  Setup script, and a -v3 log would help confirm.

- Are you on Ubuntu?  If you could install and test a cabal-install-head
  binary from https://launchpad.net/~hvr/+archive/ubuntu/ghc
  that would be helpful to find out if we've fixed this bug
  already.

- If you want to file a bug, please do so in the Cabal
  bug tracker https://github.com/haskell/cabal/issues
  Thanks!

Cheers,
Edward

Excerpts from Henk-Jan van Tuyl's message of 2017-06-04 11:45:58 +0200:
> 
> L.S.,
> 
> I am trying the prerelease of GHC, version 8.2.0.20170507
> 
> I adapted wxHaskell to the new packages that come with the new GHC and it
> compiles now, but only the first time. If I compile it a second time, even
> if nothing has changed, the information from the custom-setup section of
> the wxc.cabal file seems to be forgotten. This section looks like this:
> 
> custom-setup
>    setup-depends:
>      base,
>      Cabal < 2,
>      containers,
>      bytestring,
>      split,
>      process,
>      directory,
>      filepath
> (I am using cabal-install 1.24.0.2)
> 
> Output from the second time I try to install wxHaskell:
> 
> > cabal install --force-reinstalls --reinstall wxdirect wxc wxcore wx
> [1 of 1] Compiling Main             (
> X:\Temp\wxHaskell\wxcore\dist\setup\setup.hs,
> X:\Temp\wxHaskell\wxcore\dist\setup\Main.o )
> Linking X:\Temp\wxHaskell\wxcore\dist\setup\setup.exe ...
> [1 of 1] Compiling Main             (
> X:\Temp\wxHaskell\wxc\dist\setup\setup.hs,
> X:\Temp\wxHaskell\wxc\dist\setup\Main.o )
> 
> X:\Temp\wxHaskell\wxc\dist\setup\setup.hs:505:61: error:
>                        Variable not in scope: versionBranch :: Version ->
> [a0]
>                        |
> 505 |           full_ver = (concat . intersperse "." . map show .
> versionBranch) ver
>                        |
> ^^^^^^^^^^^^^
> 
> This error message indicates that the wrong version of Cabal (2.0) is used
> to compile the wxcore setup.hs
> It looks like a cabal-install bug, but this does not happen when I
> use GHC 8.0.2; should I write a GHC bug ticket?
> 
> Regards,
> Henk-Jan van Tuyl
> 
> 
> -- 
> Folding at home
> What if you could share your unused computer power to help find a cure? In
> just 5 minutes you can join the world's biggest networked computer and get
> us closer sooner. Watch the video.
> http://foldingathome.stanford.edu/
> 
> 
> http://Van.Tuyl.eu/
> http://members.chello.nl/hjgtuyl/tourdemonad.html
> Haskell programming