[Haskell-cafe] Build base with stack

[Edward Z. Yang]

Excerpts from Robin Palotai's message of 2017-01-05 15:42:09 +0100:
> Thanks for the pointer Edward, new-build seems nice. It could build base
> indeed!
> 
> Just a note - with the patch, if I had "tests: True" in cabal.project, I
> got an assertion for
>     pkgStanzasEnabled `Set.isSubsetOf` pkgStanzasAvailable
> from Distribution/Client/ProjectPlanning.hs. Maybe WAI.

OK, worth reporting as a bug on Cabal tracker if you have time.

> Do you think the patch could make it upstream in a form of some flag?
> --no-require-install=x,y or so.

Yes, I think this would make sense!

Edward

> Thank you,
> Robin
> 
> 2016-12-31 3:28 GMT+01:00 Edward Z. Yang <ezyang at mit.edu>:
> 
> > Excerpts from Brandon Allbery's message of 2016-12-30 19:45:46 -0500:
> > > On Fri, Dec 30, 2016 at 7:37 PM, Robin Palotai <palotai.robin at gmail.com>
> > > wrote:
> > > >
> > > > Do you know a way to force a rebuild of base with stack? I don't want
> > to
> > > > modify it, just want to feed it through a customized ghc pipeline.
> > > >
> > >
> > > base is part of ghc and must be built along with ghc. It cannot be built
> > > separately from ghc, regardless of tooling, if you want it to actually
> > work.
> > >
> > > (If you want to see some examples of why it is this way, play around with
> > > RebindableSyntax a bit, paying attention to the ways in which it breaks
> > if
> > > you do the wrong thing. You can also get some idea of it from the
> > behavior
> > > of type roles. In short: ghc must know the precise identity *at machine
> > > level*, not just source, of various key types in base. It can only do
> > this
> > > by ghc and base being built together so that various types' machine level
> > > representations can be wired into ghc as they are built.)
> >
> > Although it is true that GHC is closely tied to the particularities
> > of base, you CAN swap out base, as long as the new version of base has
> > all of the wired in entities that GHC expects to see. (This must be
> > the case, because we build stage 1 GHC before we build base.)
> >
> > To answer OP's question, I don't know how to do it with Stack but I've
> > rebuilt base with cabal-install new-build with a little patch.  First you
> > have to
> > modify cabal-install/Distribution/Solver/Modular/Solver.hs,
> > changing the invocation of P.requireInstalled so that "base" isn't
> > on the list; this lets cabal-install decide that it can rebuild base.
> > Then, in your cabal.project, add:
> >
> >     packages: path/to/base
> >     constraints: base +integer-gmp
> >
> > (The integer-gmp flag is manual so you need to make sure you toggle
> > it yourself.)  Then cabal new-build will build it, and other packages
> > will make use of it.
> >
> > Good luck!
> >
> > Edward
> >