Proposal for removing transformers dependency

[Kazu Yamamoto (=?iso-2022-jp?B?GyRCOzNLXE9CSScbKEI=?=)]

Hi,

I also hope that this is integrated into GHC 7.10.

--Kazu

> Hello.
> 
> I'm coming with a proposal for removing transformers dependency
> from ghc library. The reason for this proposal that it's not possible
> to build consistent environment where a modern libraries (that depend
> on a newer transformers or mtl-2.2) and libraries that use ghc API
> are used together. And often people are tend to use version that is
> bundled with ghc, even if newer are available.
> 
> As transformers usage are quite limited in ghc, and it's really relevant
> in ghc-bin, it's possible to duplicate the code, and provide required
> fixes in ghc-bin.cabal. As a result ghc uses it's own MonadIO, MonadControl
> and Strict State, and ghc-bin.cabal (ghc/*) uses ones from transformers.
> 
> I have prepared a proof of concept [1], however it doesn't look very clean
> and it's quite possible that will require some generalization, for example
> introduction of the ghc-transformers-instances package that will have
> all required instances.
> 
> Should I continue doing this? Are there any things to consider and fix?
> 
> [1] https://github.com/qnikst/ghc/compare/wip/remove-tf
> -- 
> Alexander