anchor.diff:  then
     buildDunePackage {
       inherit pname src meta;
  -    inherit (param) version;
  +    inherit (param) version useDune2 buildInputs;
     }
   else
     stdenv.mkDerivation {
  
positive.code:   "4.07" = {
      version = "5.1+4.06.0";
      sha256 = "1ww4cspdpgjjsgiv71s0im5yjkr3544x96wsq1vpdacq7dr7zwiw"; };
    "4.08" = v6_2;
    "4.09" = v6_2;
    "4.10" = v6_2;
    "4.11" = v6_2;
  }.${ocaml.meta.branch};
  in
  
  
negative.code: { lib, stdenv, fetchFromGitHub, buildDunePackage, ocaml, findlib, cppo }:
  
  let param =
    let v6_3 = {
      version = "6.3";
      sha256 = "1skf4njvkifwx0qlsrc0jn891gvvcp5ryd6kkpx56hck7nnxv8x6";
      useDune2 = lib.versionAtLeast ocaml.version "4.12";
      buildInputs = [cppo];
    }; in
  {
    "4.02" = {
  