Re: Fwd: compiling haskell-src-exts in 6.10

On Tue, 2008-11-11 at 12:20 +0000, Hugo Pacheco wrote:

---------- Forwarded message ---------- From: Hugo Pacheco Date: Tue, Nov 11, 2008 at 12:20 PM Subject: compiling haskell-src-exts in 6.10 To: Haskell Cafe

When installing package haskell-src-exts via cabal install, I get the error

What happened about the program 'happy'? Did it magically start working?

Language/Haskell/Exts/Syntax.hs:102:7: Could not find module `Data.Data': it is a member of package base, which is hidden

However, when manually installing

runhaskell Setup.hs configure/build/install

It works fine Somehow package base is not available in cabal.. don't know why.

Assuming you're using the latest haskell-src-exts-0.3.9 then the issue is that it does not say that it needs base-4 which is the version that exports Data.Data. The cabal-install program will pick base-3 unless the package says it needs base-4 because the vast majority of packages were written with open ended dependencies on base and will not work with base-4. What is confusing is that the configure command is not so smart and it just picks the latest version of everything (ie base-4). So that probably tricked the package author into making it work with base-4 and in the process breaking it for all older versions. So there are three workarounds, one is to get the author to fix the package. One is to fix it yourself and the other is to use an older version of the package. Duncan