anchor.diff:  
     overlays = [ overlay ];
   
  -in
  -
  -let
  +  config  = { };
  +
      nixpkgs = import ./nixpkgs.nix;
      linuxPkgs = nixpkgs { inherit config overlays; system = "x86_64-linux" ; };
     darwinPkgs = nixpkgs { inherit config overlays; system = "x86_64-darwin"; };
  
positive.code:                     haskellPackagesNew.c2hs
                    ];
  
                    patches = [ tests/tests.patch ];
  
                    postPatch = ''
                      patchShebangs tests
                      substituteInPlace tests/simple-client.sh \
                        --replace @makeWrapper@ ${pkgsNew.makeWrapper} \
  
negative.code: 
      grpc                       =       pkgs.grpc;
  
      inherit pkgs config overlay;
      inherit (pkgs) test-grpc-haskell;
    }
  