flake.nix,flake.lock: prepare rust environment

flake.nix

@@ -1,7 +1,12 @@
 {
-  inputs.nixpkgs.url = "nixpkgs/nixpkgs-unstable";
+  inputs = {
+    nixpkgs.url = "nixpkgs/nixpkgs-unstable";
 
-  outputs = { self, nixpkgs }: let
+    rust-overlay.url = "github:oxalica/rust-overlay";
+    rust-overlay.inputs.nixpkgs.follows = "nixpkgs";
+  };
+
+  outputs = { self, nixpkgs, rust-overlay }: let
     inherit (nixpkgs) lib;
 
     systems = [
@@ -12,16 +17,33 @@
       "armv7l-linux"
     ];
 
-    forAllSystems = f: lib.genAttrs systems (system: f system nixpkgs.legacyPackages.${system});
+    forAllSystems = f: nixpkgs.lib.genAttrs systems (system: let
+      pkgs = import nixpkgs {
+        inherit system;
+        overlays = [
+          (import rust-overlay)
+        ];
+      };
+
+      rust-bin = rust-overlay.lib.mkRustBin { } pkgs.buildPackages;
+      toolchain = rust-bin.stable.latest.default.override {
+        extensions = [ "rust-src" ];
+      };
+    in f system pkgs toolchain);
   in {
-    devShells = forAllSystems (system: pkgs: {
+    devShells = forAllSystems (system: pkgs: toolchain: {
       default = pkgs.mkShell {
         packages = with pkgs; [
+          toolchain
+          cargo-edit
+
           ruff
           (python3.withPackages (ppkgs: with ppkgs; [
             psycopg2-binary
           ]))
         ];
+
+        env.RUST_SRC_PATH = "${toolchain}/lib/rustlib/src/rust/library";
       };
     });
 
@@ -31,7 +53,7 @@
 
     nixosModules.default = ./module.nix;
 
-    packages = forAllSystems (system: pkgs: {
+    packages = forAllSystems (system: pkgs: _: {
       default = self.packages.${system}.mclog2psql;
       mclog2psql = pkgs.writers.writePython3Bin "mclog2psql" {
         libraries = [ pkgs.python3Packages.psycopg2 ];