[Nix-dev] Haskell-env (via nix-shell) - am I doing this right?

[Peter Simons]

Hi Matthias,

 >     $ cabal build
 >     Building ratehs-0.1...
 >     Preprocessing executable 'ratehs' for ratehs-0.1...
 >     <command line>: cannot satisfy -package-id
 >     snap-0.14.0.2-ef658c66823be8387d049aa89445f690:
 >     snap-0.14.0.2-ef658c66823be8387d049aa89445f690 is unusable due
 >     to missing or recursive dependencies:
 >     clientsession-0.9.1.1-f379c9ed2e350715ba6cdc20d73894b3
 >     (use -v for more information)
 >
 > Do you have an idea how I can fix this?

this issue is described in https://github.com/NixOS/nixpkgs/issues/7792.
Instructions how to recover from this problem are in this thread. The
short version is: garbage collect "haskell-clientsession" and all its
dependents, then download those packages from scratch (or build them
locally with --option build-use-substitutes false. Anyway, the ticket
has more information on this subject.

Best regards,
Peter