nix: add nil nix lsp to shell

flake.lock

@@ -1,6 +1,57 @@
 {
   "nodes": {
+    "flake-utils": {
+      "locked": {
+        "lastModified": 1659877975,
+        "narHash": "sha256-zllb8aq3YO3h8B/U0/J1WBgAL8EX5yWf5pMj3G0NAmc=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "c0e246b9b83f637f4681389ecabcb2681b4f3af0",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nil": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs",
+        "rust-overlay": "rust-overlay"
+      },
+      "locked": {
+        "lastModified": 1663265701,
+        "narHash": "sha256-0sZULukbNmlhkH2+dwWK83zN5gRaZCoUBlSjMENg2o8=",
+        "owner": "oxalica",
+        "repo": "nil",
+        "rev": "9e395607ad6dd8e771b8b0979ae738e845e7000c",
+        "type": "github"
+      },
+      "original": {
+        "owner": "oxalica",
+        "repo": "nil",
+        "type": "github"
+      }
+    },
     "nixpkgs": {
+      "locked": {
+        "lastModified": 1662096612,
+        "narHash": "sha256-R+Q8l5JuyJryRPdiIaYpO5O3A55rT+/pItBrKcy7LM4=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "21de2b973f9fee595a7a1ac4693efff791245c34",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs_2": {
       "locked": {
         "lastModified": 1663146586,
         "narHash": "sha256-VCGdyEc5TF0uq+gdU+jesjZcNxptomDunvGtElmAD9I=",
@@ -18,10 +69,36 @@
     },
     "root": {
       "inputs": {
-        "nixpkgs": "nixpkgs",
+        "nil": "nil",
+        "nixpkgs": "nixpkgs_2",
         "utils": "utils"
       }
     },
+    "rust-overlay": {
+      "inputs": {
+        "flake-utils": [
+          "nil",
+          "flake-utils"
+        ],
+        "nixpkgs": [
+          "nil",
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1662173844,
+        "narHash": "sha256-+ZgW98Y8fZkgFSylE+Mzalumw+kw3SVivZznbJqQaj8=",
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "rev": "8ac6d40380dc4ec86f1ff591d5c14c8ae1d77a18",
+        "type": "github"
+      },
+      "original": {
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "type": "github"
+      }
+    },
     "utils": {
       "locked": {
         "lastModified": 1659877975,

flake.nix

@@ -2,18 +2,22 @@
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
     utils.url = "github:numtide/flake-utils";
+
+    # nix lsp
+    nil.url = "github:oxalica/nil";
   };
 
-  outputs = { self, nixpkgs, utils }:
+  outputs = input @ { self, nixpkgs, utils, ... }:
     utils.lib.eachDefaultSystem (system:
       let
         pkgs = import nixpkgs { inherit system; };
 
         neovim = pkgs.callPackage ./. { };
+        nil = input.nil.packages.${system}.nil;
       in
       {
         devShells.default = pkgs.mkShell {
-          packages = [ neovim ];
+          packages = [ neovim nil ];
         };
       });
 }