e0/flake.nix

{
  inputs = {
    utils.url = "github:numtide/flake-utils";
    fenix.url = "github:nix-community/fenix";
    fenix.inputs.nixpkgs.follows = "nixpkgs";
  };

  outputs = { self, nixpkgs, utils, fenix }:
    utils.lib.eachDefaultSystem (system:
      let
        pkgs = import nixpkgs {
          inherit system;
          overlays = [ fenix.overlay ];
        };
        toolchain = pkgs.fenix.complete;
        myPkgs = rec { e0 = pkgs.callPackage ./. { inherit toolchain; }; };

      in rec {
        devShell = pkgs.mkShell {
          packages = with pkgs;
            with pkgs.llvmPackages_12; [
              cargo-edit
              cargo-watch
              clangUseLLVM
              (toolchain.withComponents [ "clippy" "rustc" "rust-src" ])
            ];
          inputsFrom = with myPkgs; [ e0 ];
          CARGO_UNSTABLE_SPARSE_REGISTRY = "true";
        };

        packages = utils.lib.flattenTree myPkgs;
        defaultPackage = packages.e0;
      });
}