Problem: I am trying to upgrade haskell stack from version 1.4.0 to .1.5.1 in NixOS.
In my configuration.nix:
environment.systemPackages = with pkgs; [
# ...
stack
# ...
];
On nixpkgs, it says that stack should be on version 1.5.1:
Yet:
$ stack --version
Version 1.4.0 x86_64
The packages listed on https://nixos.org/nixos/packages.html reflect the current stable release of NixOS, which is currently 17.09.
Stack 1.5.1 became available on that very same release, 17.09. To install Stack 1.5.1 you need to be either on the NixOS unstable branch or on NixOS 17.09. It seems you're currently on NixOS 17.03.