On Thu, Sep 18, 2008 at 1:36 AM, Eric Kow <[EMAIL PROTECTED]> wrote:
>
> I'm trusting you and the community on this one because I could not build
> the latest haskeline.  Cabal upgrade haskeline gives me this, trying to
> build 0.3.1 (my bytestring version is 0.9.1.2)
>
> [ 5 of 17] Compiling System.Console.Haskeline.Command.History (
> System/Console/Haskeline/Command/History.hs,
> dist/build/System/Console/Haskeline/Command/History.o )
>
> System/Console/Haskeline/Command/History.hs:41:45:
>    Couldn't match expected type `UTF8.ByteString'
>           against inferred type `B.ByteString'
>      Expected type: IO UTF8.ByteString
>      Inferred type: IO B.ByteString
>    In the second argument of `fmap', namely `(B.readFile file)'
>    In the expression:
>        if exists then fmap UTF8.toString (B.readFile file) else return
> ""

I've seen that problem come up myself; the issue is Cabal not picking
consistent package versions.  Namely:
- haskeline depends on the utf8-string and bytestring packages
- utf8-string depends on bytestring
And haskeline gets built with a newer version of bytestring than
utf8-string depends on,  causing a type error.

I just tried and was unable to reproduce the above, so it may be fixed
in the latest version of cabal-install (0.5.2).  Otherwise, I've been
able to fix this issue by unregistering utf8-string and "cabal
install"ing it again to depend on the latest installed version of
bytestring.  Then "cabal upgrade haskeline" should work fine.

As an aside: although darcs doesn't require haskeline as a dependency,
I personally consider its cross-platform availability to be a high
priority of the project.  Thus, any reports of not being able to build
haskeline are welcome and considered to be bugs unless found otherwise
(as above).

-Judah
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