Fix and simplify flake.nix

Author: sveitser

flake.lock

@@ -1,66 +1,27 @@
 {
-  description = "Nll crate";
+  description = "A devShell example";
 
-  nixConfig = {
-    extra-substituters = [ "https://espresso-systems-private.cachix.org" ];
-    extra-trusted-public-keys = [
-      "espresso-systems-private.cachix.org-1:LHYk03zKQCeZ4dvg3NctyCq88e44oBZVug5LpYKjPRI="
-    ];
-  };
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+  inputs.rust-overlay.url = "github:oxalica/rust-overlay";
+  inputs.flake-utils.url = "github:numtide/flake-utils";
 
-  inputs = {
-    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
-    utils.url = "github:numtide/flake-utils";
-    flake-compat = {
-      url = "github:edolstra/flake-compat";
-      flake = false;
-    };
-    fenix = {
-      url = "github:nix-community/fenix";
-      inputs.nixpkgs.follows = "nixpkgs";
-    };
-  };
-
-  outputs =
-    { self, nixpkgs, flake-compat, utils, fenix }:
-    utils.lib.eachDefaultSystem (system:
+  outputs = { nixpkgs, rust-overlay, flake-utils, ... }:
+    flake-utils.lib.eachDefaultSystem (system:
       let
-        fenixStable = fenix.packages.${system}.stable.withComponents [
-          "cargo"
-          "clippy"
-          "rust-src"
-          "rustc"
-          "rustfmt"
-          "llvm-tools-preview"
-        ];
-
-        CARGO_TARGET_DIR = "target_dirs/nix_rustc";
-
-        rustOverlay = final: prev: {
-          rustc = fenixStable;
-          cargo = fenixStable;
-          rust-src = fenixStable;
-        };
-
+        overlays = [ (import rust-overlay) ];
         pkgs = import nixpkgs {
-          inherit system;
-          overlays = [ rustOverlay ];
+          inherit system overlays;
         };
-
-        buildDeps = with pkgs;
-          [
-            nixpkgs-fmt
-            fenix.packages.${system}.rust-analyzer
-          ] ++ lib.optionals stdenv.isDarwin [
-            darwin.apple_sdk.frameworks.Security
-            pkgs.libiconv
-            darwin.apple_sdk.frameworks.SystemConfiguration
+      in
+      with pkgs;
+      {
+        CARGO_TARGET_DIR = "target_dirs/nix_rustc";
+        devShells.default = mkShell {
+          buildInputs = [
+            just
+            rust-bin.stable.latest.default
           ];
-      in {
-        devShell = pkgs.mkShell {
-          inherit CARGO_TARGET_DIR;
-          buildInputs = [ fenixStable ] ++ buildDeps;
         };
-
-      });
+      }
+    );
 }