Drastic Prelude changes imminent

[Herbert Valerio Riedel]

On 2015-01-27 at 18:25:21 +0100, Gershom B wrote:

[...]

> We could perhaps also insert a warning encouraging people to import
> Data.List qualified, either in this GHC of the next release. This
> would allow BBP to proceed in a relatively breakage-free way in the
> future without needing to generalize the Data.List module.

Ironically, the AMP-related warnings in GHC 7.8 weren't very effective
at getting noticed timely in order to have Hackage ready for the actual
AMP-changes occurring in GHC 7.10. By far the most breakages[1] I
encountered (and reported) over the last weeks in
popularly-depended-upon packages were due to missing Functor/Applicative
instances. It'd be interesting to know why those warnings weren't
acted upon during 2014.

Otoh, I don't have numbers how many packages were actually fixed up
*thanks* to the GHC 7.8 warnings...


 [1]: FWIW, the AMP is a serious breaking change due to its nature of
      introducing a superclass constraint *incompatible* with H2010 as
      H2010 doesn't even know anything about the Applicative class to
      begin with...

      The BBP, on the other hand, in its incarnation as of GHC 7.10.1RC2
      was designed to be a smooth upgrade path for existing H2010 code
      as it just generalises type-signatures, and does not even require
      any CPP to write code that compiles with both, a strict
      Haskell2010 compiler+base-library, as well with GHC 7.10.1RC2's
      F/T-generalised base-library.

Cheers,
  hvr