[Nix-dev] ghcWithPackages appears broken in nixpkgs HEAD?

[Peter Simons]

Hi Michael,

my guess is that you've run into a design problem in GHC that causes the
compiler to assign randomly differing package IDs every now and then.
The result is that libraries built locally don't fit to ones downloaded
from Hydra. The only way out of this mess is to garbage collect all
Haskell packages by running

  $ nix-store --delete /nix/store/*-ghc-7.8.4

and to compile or download everything again from scratch.

Best regards,
Peter