anchor.diff:    pname = "ppxlib";
     inherit version;
   
  -  useDune2 = param.useDune2 or false;
  +  useDune2 = param.useDune2 or true;
   
     src = fetchFromGitHub {
       owner = "ocaml-ppx";
  
positive.code: { lib, fetchFromGitHub, buildDunePackage, ocaml
  , version ? if lib.versionAtLeast ocaml.version "4.07" then "0.15.0" else "0.13.0"
  , ocaml-compiler-libs, ocaml-migrate-parsetree, ppx_derivers, stdio
  , stdlib-shims
  }:
  
  let param = {
    "0.8.1" = {
      sha256 = "0vm0jajmg8135scbg0x60ivyy5gzv4abwnl7zls2mrw23ac6kml6";
      max_version = "4.10";
    };
    "0.13.0" = {
      sha256 = "0c54g22pm6lhfh3f7s5wbah8y48lr5lj3cqsbvgi99bly1b5vqvl";
    };
    "0.15.0" = {
      sha256 = "1p037kqj5858xrhh0dps6vbf4fnijla6z9fjz5zigvnqp4i2xkrn";
      min_version = "4.07";
      useDune2 = true;
    };
  }."${version}"; in
  
  
negative.code:   };
  
    propagatedBuildInputs = [
      ocaml-compiler-libs
      (if param.useOMP2 or true
       then ocaml-migrate-parsetree-2-1
       else ocaml-migrate-parsetree)
      ppx_derivers
      stdio
      stdlib-shims
    ];
  
  