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 ];
        };
        # https://github.com/NixOS/nixpkgs/issues/148117
        llvmPkgs = pkgs.pkgsStatic.llvmPackages_12;
        myPkgs = rec { e0 = pkgs.callPackage ./. { inherit llvmPkgs; }; };

      in rec {
        devShell = pkgs.mkShell {
          packages = with pkgs; [ llvmPkgs.clangUseLLVM cargo-watch ];
          inputsFrom = with myPkgs; [ e0 ];
          CARGO_UNSTABLE_SPARSE_REGISTRY = "true";
          LLVM_SYS_120_PREFIX = "${llvmPkgs.llvm.dev}";
        };

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