Use with Emacs? about nix-cl HOT 1 OPEN

sbcl.override { 
  packageOverlays = self: super: { 
    alexandria = pkgs.hello; 
  }; 
} 

let
  alexandria = sbcl.buildASDFSystem rec {
    pname = "alexandria";
    version = "1.4";
    src = fetchFromGitLab {
      domain = "gitlab.common-lisp.net";
      owner = "alexandria";
      repo = "alexandria";
      rev = "v${version}";
      hash = "sha256-1Hzxt65dZvgOFIljjjlSGgKYkj+YBLwJCACi5DZsKmQ=";
    };
  };
  sbcl' = sbcl.withOverrides (self: super: {
    inherit alexandria;
  });
in sbcl'.pkgs.alexandria

{
  description = "cl-dev";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = inputs@{ flake-utils, nixpkgs, ... }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = import nixpkgs {
          inherit system;
          config.allowUnfree = true;
          overlays = [ ];
        };
        sbcl = pkgs.sbcl.withOverrides (self: super: {
          slynk = super.slynk.overrideLispAttrs (o: {
            systems = o.systems ++ [ "slynk/mrepl" ];
          });
          slynk-stepper = pkgs.sbcl.buildASDFSystem {
            pname = "slynk-stepper";
            version = "9999";
            src = pkgs.fetchFromGitHub {
              owner = "joaotavora";
              repo = "sly-stepper";
              rev = "da84e3bba8466c2290c2dc7c27d7f4c48c27b39e";
              sha256 = "sha256-gMbmG42gxaQrgDUVySbGGpayxDM3pKAgDvYpd9KZ4B4=";
            };
            lispLibs = [ self.slynk super.agnostic-lizard ];
          };
        });
        local-sbcl = sbcl.withPackages (ps: with ps; [
          slynk
          slynk-stepper
          hunchentoot
        ]);
      in {
        devShells.default = pkgs.mkShell rec {
          name = "cl-dev";
          packages = [ local-sbcl pkgs.nixfmt-rfc-style ];
        };
      });
}