GHC 8 and Template Haskell

[Herbert Valerio Riedel]

On 2016-04-15 at 00:04:05 +0200, Iavor Diatchki wrote:
> Sure, I'd be happy to help whoever needs help---just let me know.

Great... :-)

> The change that one would have to do is:  whenever you'd used "InstaceD"
>  replace it with "InstanceD Nothing".

I've done a quick grep for InstanceD over the stackage-nightly-subset of Hackage:

 https://gist.githubusercontent.com/hvr/97a4f0f0f594faa9c17857b52add9a2e

so those are most likely the packages (within the stackage-subset) that
will lose their GHC 8.0-readyness (if they had it to begin with...).

As a popular package example, `lens-4.13.{1,2,2.1}` has been GHC
8.0-ready for 3 releases already; so this would require retroactively
blocking those 3 releases by tightening the template-haskell upper-bound
via cabal-edits, and making a new release of `lens` as soon as GHC 8.0
final (or RC4) gets released...

On the bright side, the amount of packages affected seems manageable...