Fwd: compiling haskell-src-exts in 6.10

[Duncan Coutts]

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

> ---------- Forwarded message ----------
> From: Hugo Pacheco <hpacheco at gmail.com>
> Date: Tue, Nov 11, 2008 at 12:20 PM
> Subject: compiling haskell-src-exts in 6.10
> To: Haskell Cafe <haskell-cafe at haskell.org>
> 
> 
> 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