addressing review comments

default.nix

@@ -18,11 +18,7 @@ with pkgs.lib;
 with pkgs.haskell.lib;
 
 let
-  plutusPkgs = ((import ./pkgs { inherit pkgs; }).override {
-    ghc = overrideDerivation pkgs.haskell.compiler.ghc822 (drv: {
-      patches = drv.patches ++ [ ./ghc-8.0.2-darwin-rec-link.patch ];
-    });
-  });
+  plutusPkgs = import ./pkgs { inherit pkgs; };
   cleanSourceFilter = with pkgs.stdenv;
     name: type: let baseName = baseNameOf (toString name); in ! (
       # Filter out .git repo
@@ -47,8 +43,7 @@ let
     tests = {
       shellcheck = pkgs.callPackage ./tests/shellcheck.nix { src = ./.; };
       hedgehog = pkgs.callPackage ./tests/hedgehog.nix {
-        inherit pkgs plutusPkgs;
-        source = ./.;
+        inherit pkgs plutusPkgs source;
       };
     };
     stack2nix = import (pkgs.fetchFromGitHub {

fetch-nixpkgs.nix

@@ -1,8 +1,13 @@
 let
   # temporary hack until scripts/nix-shell.sh ceases to use -p
-  pkgs_path = import ./fetchNixpkgs.nix (builtins.fromJSON (builtins.readFile ./nixpkgs-src.json));
+  fetchNixpkgs = rev: sha256unpacked: builtins.fetchTarball {
+    url = "https://github.com/NixOS/nixpkgs/archive/${rev}.tar.gz";
+    sha256 = sha256unpacked;
+  };
+  nixpkgsJson = builtins.fromJSON (builtins.readFile ./nixpkgs-src.json);
+  pkgs_path = fetchNixpkgs nixpkgsJson.rev nixpkgsJson.sha256unpacked;
   pkgs = import pkgs_path { config = {}; overlays = []; };
-  wrapped = pkgs.runCommand "nixpkgs" {} ''
-    ln -sv ${pkgs_path} $out
-  '';
-in if 0 <= builtins.compareVersions builtins.nixVersion "1.12" then wrapped else pkgs_path
+in
+pkgs.runCommand "nixpkgs" {} ''
+  ln -sv ${pkgs_path} $out
+''

lib.nix

@@ -1,6 +1,6 @@
 let
-  # Allow overriding pinned nixpkgs for debugging purposes via cardano_pkgs
-  fetchNixPkgs = let try = builtins.tryEval <cardano_pkgs>;
+  # Allow overriding pinned nixpkgs for debugging purposes via plutus_pkgs
+  fetchNixPkgs = let try = builtins.tryEval <plutus_pkgs>;
     in if try.success
     then builtins.trace "using host <plutus_pkgs>" try.value
     else import ./fetch-nixpkgs.nix;