pin nixpkgs and prepare shell.nix

build-shell.nix

 {ghc}:
-with (import <nixpkgs> {});
+with (import ./pinned.nix {});
 
 haskell.lib.buildStackProject {
   inherit ghc;

pinned.nix

+import (
+  builtins.fetchTarball {
+    url = "https://github.com/nixos/nixpkgs/archive/ece829033b7b8f4e81261fef5427144df4147bc4.tar.gz";
+    sha256 = "07n91k3d9i9pym8npsszha9mnvg4d1r0l0ldnhk4g8sx15vv1br5";
+  }
+)

default.nix → shell.nix

-with (import <nixpkgs> {});
-stdenv.mkDerivation rec {
-  name = "env";
-  env = buildEnv {
-    name = name;
-    paths = buildInputs;
-  };
-  buildInputs = [
+{ pkgs ? import ./pinned.nix {} }:
+
+pkgs.mkShell {
+  buildInputs = with pkgs; [
     docker-compose
     #glibc
     #gmp
@@ -16,8 +12,4 @@ stdenv.mkDerivation rec {
     #stack
     #xz
   ];
-  builder = builtins.toFile "builder.sh" ''
-    source $stdenv/setup
-    touch $out
-  '';
 }