default.nix

self: super:

let
  hostPkgs = import <nixpkgs> {};
  # Look here for information about how to generate `nixpkgs-version.json`.
  #  → https://nixos.wiki/wiki/FAQ/Pinning_Nixpkgs
  pinnedVersion = hostPkgs.lib.importJSON ./nixpkgs-version.json;
  pinnedPkgs = hostPkgs.fetchFromGitHub {
    owner = "NixOS";
    repo = "nixpkgs-channels";
    inherit (pinnedVersion) rev sha256;
  };
in

{
  haskell.packages.greenclip = pinnedPkgs.haskell.packages.greenclip;
}

getting an error:

$ nix-build '<nixpkgs>' -A haskellPackages.greenclip
error: attribute 'ghc843' missing, at /home/kalbasit/.config/nixpkgs/external/nixpkgs/pkgs/top-level/all-packages.nix:6561:21
(use '--show-trace' to show detailed location information)