anchor.diff:          rev = "1c04f5664b9476e0b01a573b40462531e52e8756";
           sha256 = "0j121551zqjrp4xy0qcz1pk46znr6w59jkg75v5svdh9ag3vmbsp";
         };
  +
  +      megaparsec = pkgs.fetchFromGitHub {
  +        owner  = "mrkkrp";
  +        repo   = "megaparsec";
  +        rev    = "7b271a5edc1af59fa435a705349310cfdeaaa7e9";
  +        sha256 = "0415z18gl8dgms57rxzp870dpz7rcqvy008wrw5r22xw8qq0s13c";
  +      };
  +
  +      parser-combinators = pkgs.fetchFromGitHub {
  +        owner  = "mrkkrp";
  +        repo   = "parser-combinators";
  +        rev    = "dd6599224fe7eb224477ef8e9269602fb6b79fe0";
  +        sha256 = "11cpfzlb6vl0r5i7vbhp147cfxds248fm5xq8pwxk92d1f5g9pxm";
  +      };
  +
       };
       toolOverrides = ghc: super: {
         z3 = pkgs.z3;
  
positive.code:       ghc = ["pact"];
        # ghcjs = ["pact"];
      };
    
    })
  
negative.code:             aeson = self.callHackage "aeson" "1.1.2.0" {};
              blake2 = guardGhcjs super.blake2;
              haskeline = guardGhcjs super.haskeline;
  
              # Needed to get around a requirement on `hspec-discover`.
              megaparsec = pkgs.haskell.lib.dontCheck super.megaparsec;
  
              # Needed to build with the below version of statistics
              criterion = self.callCabal2nix "criterion" (pkgs.fetchFromGitHub {
  