realised that rustfmt nightly is in nixpkgs already lol :3

homes/modules/programs/neovim/nixcats.nix

@@ -67,7 +67,7 @@ in {
             rust = {
               lsp = [cargo mpkgs.rust-analyzer];
               # nightly rustfmt has nicer features :3
-              format = [inputs.fenix.packages.${system}.complete.rustfmt];
+              format = [(rustfmt.override {asNightly = true;})];
             };
             zig = {
               lsp = [zls];