stack-shell.nix_

let
  hsPkgs = (import ./default.nix);
  src = builtins.fetchTarball https://github.com/input-output-hk/haskell.nix/archive/master.tar.gz;
  pkgs = import (src + "/nixpkgs") (import src);

  mypkgs = import <nixpkgs> {};

  # nixpkgsUnstable =
  #   let
  #     # sudo nix-channel --add https://nixos.org/channels/nixpkgs-unstable nixpkgs-unstable
  #     nixpkgs-unstable-src = fetchTarball https://nixos.org/channels/nixpkgs-unstable/nixexprs.tar.xz;
  #     # nixpkgs-unstable-src = <nixpkgs-unstable>;
  #   in import nixpkgs-unstable-src { config = { allowUnfree = true; }; };
in


hsPkgs.shellFor {
  # Shell will provide the dependencies, but not packages themselves.
  packages = ps: with ps; [ generate-all-tests ];
  # This adds cabal-install to the shell, which helps tests because
  # they use a nix-shell --pure. Normally you would BYO cabal-install.
  buildInputs = with pkgs; [ mypkgs.cabal-install nix zlib ];
  exactDeps = true;
  STACK_IN_NIX_SHELL = true;
}