Proposal for removing transformers dependency

[Simon Peyton Jones]

|  One thing to keep in mind though is that then 'haskeline' (which is
|  needed by GHCi) still remains a consumer of 'transformers', so we'd
|  still have to bundle a 'transformers' package version with GHC even if
|  `ghc` doesn't depend on it anymore. Somewhat related, the `ghc` ->

couldn't we invite Judah to remove the transformers dependency for haskeline?

It all seems a bit late for 7.10.

Simon

|  -----Original Message-----
|  From: ghc-devs [mailto:ghc-devs-bounces at haskell.org] On Behalf Of
|  Herbert Valerio Riedel
|  Sent: 22 January 2015 07:37
|  To: Alexander V Vershilov
|  Cc: ghc-devs at haskell.org
|  Subject: Re: Proposal for removing transformers dependency
|  
|  On 2015-01-21 at 17:19:42 +0100, Alexander V Vershilov wrote:
|  > I thought about providing package ghc-transformers-instances, that
|  > will provide instances for transformers's type classes for user. So
|  > ghc-tf-instances will depend on current ghc, and current
|  transformers
|  > that could be provided by user environment.
|  
|  So the price is seems to be mostly to tolerate orphan instances (and
|  potentially having to copy more code from transformers into ghc, if
|  one wants to use more features in ghc's code).
|  
|  One would have to make sure to keep that package updated everytime a
|  new transformers or ghc package version is released, as well as making
|  sure to always test all supported combinations of ghc/transformers
|  versions before making a new releases.
|  
|  One thing to keep in mind though is that then 'haskeline' (which is
|  needed by GHCi) still remains a consumer of 'transformers', so we'd
|  still have to bundle a 'transformers' package version with GHC even if
|  `ghc` doesn't depend on it anymore. Somewhat related, the `ghc` ->
|  `Cabal` dependency was broken up in GHC 7.10 but we'll still bundle
|  `Cabal` with GHC 7.10.
|  
|  I'm not sure how much this helps Stackage which I assume would
|  constraint transformers to a single version, and therefore force a
|  reinstall of the haskeline version shipped with GHC with a different
|  version of transformers.
|  
|  Fwiw, I welcome decoupling libraries from the GHC distribution as
|  every exposed library adds to the synchronisation-with-upstream-
|  overhead when preparing new GHC releases, in addition to adding
|  implicit version constraints to the package database.
|  
|  With a GHC release-management hat on though: As for GHC 7.10.1, it's
|  rather late... at the very least it needs to get into RC2 (whose cut
|  off is tomorrow) for that to happen.
|  
|  Cheers,
|    hvr
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