anchor.diff:          hsPkgs = haskellPackages_ghc763;
       };
   
  -    ghcEnv_783 = ghcEnv {
  +    ghcSpec_783 = {
           name = "ghc783";
           ghc = ghc.ghc783;
           hsPkgs = haskellPackages_ghc783;
       };
  +
  +    ghcEnv_783 = ghcEnv ghcSpec_783;
   
       vcsTools = self.buildEnv {
           name = "vcsTools";
  
positive.code:             lens
          ];
  
      };
  }
  
negative.code: pkgs :
  {
    allowUnfree = true;
    allowBroken = true;
    packageOverrides = self: with self; rec {
  
      haskellTools = spec: ([
  