anchor.diff: -{ fetchFromGitHub, lib, which, ocamlPackages }:
  +{ fetchFromGitHub, fetchpatch, lib, which, ocamlPackages }:
   
   let
     pname = "alt-ergo";
  
positive.code: 
  let alt-ergo-parsers = ocamlPackages.buildDunePackage rec {
    pname = "alt-ergo-parsers";
    inherit version src useDune2;
    configureFlags = [ pname ];
    nativeBuildInputs = [ which ocamlPackages.menhir ];
    propagatedBuildInputs = [ alt-ergo-lib ] ++ (with ocamlPackages; [ camlzip psmt2-frontend ]);
  
negative.code: 
  ocamlPackages.buildDunePackage {
  
    inherit pname version src;
  
    # Ensure compatibility with Menhir ≥ 20211215
    patches = fetchpatch {
      url = "https://github.com/OCamlPro/alt-ergo/commit/0f9c45af352657c3aec32fca63d11d44f5126df8.patch";
      sha256 = "sha256:0zaj3xbk2s8k8jl0id3nrhdfq9mv0n378cbawwx3sziiizq7djbg";
    };
  
    configureFlags = [ pname ];
  
  