anchor.diff:  
   ocamlPackages.buildDunePackage {
   
  -  inherit pname version src useDune2;
  +  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 ];
   
  
positive.code: { fetchFromGitHub, lib, which, ocamlPackages }:
  
  let
    pname = "alt-ergo";
  
negative.code:     rev = version;
      sha256 = "0hglj1p0753w2isds01h90knraxa42d2jghr35dpwf9g8a1sm9d3";
    };
  in
  
  let alt-ergo-lib = ocamlPackages.buildDunePackage rec {
    pname = "alt-ergo-lib";
    inherit version src;
    configureFlags = [ pname ];
    nativeBuildInputs = [ which ];
    buildInputs = with ocamlPackages; [ dune-configurator ];
  