Shared data type for extension flags

Reid Barton rwbarton at
Thu Sep 3 16:51:03 UTC 2015

On Thu, Sep 3, 2015 at 12:41 PM, Herbert Valerio Riedel <hvriedel at>

> On 2015-09-02 at 10:00:40 +0200, Matthew Pickering wrote:
> > Surely the easiest way here (including for other tooling - ie
> > haskell-src-exts) is to create a package which just provides this
> > enumeration. GHC, cabal, th, haskell-src-exts and so on then all
> > depend on this package rather than creating their own enumeration.
> I'm not sure this is such a good idea having a package many packages
> depend on if `ghc` is one of them, as this forces every install-plan
> which ends up involving the ghc package to be pinned to the very same
> version the `ghc` package was compiled against.
> This is a general problem affecting packages `ghc` depends upon (and as
> a side-note starting with GHC 7.10, we were finally able to cut the
> package-dependency between `ghc` and `Cabal`)

Surely this argument does not apply to a package created to hold data types
that would otherwise live in the template-haskell or ghc packages.

Reid Barton
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