Cabal constraint solver

[Christian Höner zu Siederdissen]

Hi,

does the Cabal constraint solver always try to solve the complete graph?

example: (ghc-7.0.0-rc1)

$ cabal install parsec-3.1.0
cabal: cannot configure syb-0.2.1. It requires base >=4.0 && <4.3

cd syb-0.2.1
* remove base<4.3 constraint from syb.cabal
cabal install
* syb-0.2.1 is now installed and works!

$ cabal install parsec-3.1.0
cabal: cannot configure syb-0.2.1. It requires base >=4.0 && <4.3



This is rather annoying: the constraint is solved (eg. syb is installed)
but we /still/ assume that we can not continue. So obviously, I would
like to be able to have cabal assume constraints fullfilled if the
package is installed.

Am I missing something? (Otherwise, testing packages with 7-rc1 is
becoming annoying as almost everything depends on syb)

===

And a second thing: cabal fetch
How does one disable the solver for fetching packages? It is a bit
annoying (here too) that 'cabal fetch parsec-3.1.0' fails. (It should
maybe warn that constraints can not be fulfilled but the idea here is to
get the packages to change them manually)

===

So did I miss anything or can I write a bug report? ;-)



Gruss,
Christian

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