enabled clippy

nac3core/src/lib.rs

@@ -1,3 +1,6 @@
+#![warn(clippy::all)]
+#![allow(clippy::clone_double_ref)]
+
 extern crate num_bigint;
 extern crate inkwell;
 extern crate rustpython_parser;

shell.nix

@@ -4,6 +4,6 @@ in
   pkgs.stdenv.mkDerivation {
     name = "nac3-env";
     buildInputs = with pkgs; [
-      llvm_10 clang_10 cargo rustc libffi libxml2
+      llvm_10 clang_10 cargo rustc libffi libxml2 clippy
     ];
   }