wither the Platform

[Erik Hesselink]

On Sun, Mar 22, 2015 at 11:24 AM, Herbert Valerio Riedel <hvr at gnu.org> wrote:
> On 2015-03-22 at 11:17:21 +0100, Erik Hesselink wrote:
>
> [...]
>
>> I do this for template-haskell, since it's not possible to reinstall
>> but cabal would occasionally try it. I can imagine it would work well
>> to prevent the scenario you describe with network.
>
> Why isn't it possible to reinstall TH (unless you also need to depend on
> the `ghc` package)? We even explicitly allowed template-haskell to be
> reinstallable again in Cabal as there didn't seem any reason to forbid
> it anymore (it's no different than e.g. `bytestring` which is
> reinstallable as well):
>
>   https://github.com/haskell/cabal/commit/ffd67e5e630766906e6f4c6655c067a79f739150

This was based on my experiences from some time ago. Looking at it
now, I think it was just that the dependencies for template-haskell
were too loose, i.e. it allowed different major versions of base. When
a new version of GHC was released and I was trying it out, it would
always try to install the older version, and this never worked. Now
that you fixed these constraints (thanks!) it seems you can reinstall,
as long as it's the same (major) version. It still prints this ominous
warning even in a sandbox:

    Warning: The following packages are likely to be broken by the reinstalls:
    ghc-7.8.3

But everything seems to be fine when passing --force. So I guess I can
remove the constraint...

Erik