chore: Update Lean to v4.21.0

flake.lock

@@ -39,9 +39,7 @@
     "lean4-nix": {
       "inputs": {
         "flake-parts": "flake-parts_2",
-        "nixpkgs": [
-          "nixpkgs"
-        ]
+        "nixpkgs": "nixpkgs"
       },
       "locked": {
         "lastModified": 1750369222,
@@ -59,16 +57,16 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1750151854,
-        "narHash": "sha256-3za+1J9FifMetO7E/kwgyW+dp+8pPBNlWKfcBovnn6M=",
+        "lastModified": 1743095683,
+        "narHash": "sha256-gWd4urRoLRe8GLVC/3rYRae1h+xfQzt09xOfb0PaHSk=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "ad5c70bcc5cc5178205161b7a7d61a6e80f6d244",
+        "rev": "5e5402ecbcb27af32284d4a62553c019a3a49ea6",
         "type": "github"
       },
       "original": {
         "owner": "nixos",
-        "ref": "nixos-24.11",
+        "ref": "nixos-unstable",
         "repo": "nixpkgs",
         "type": "github"
       }
@@ -100,11 +98,27 @@
         "url": "https://github.com/NixOS/nixpkgs/archive/fb192fec7cc7a4c26d51779e9bab07ce6fa5597a.tar.gz"
       }
     },
+    "nixpkgs_2": {
+      "locked": {
+        "lastModified": 1751048012,
+        "narHash": "sha256-MYbotu4UjWpTsq01wglhN5xDRfZYLFtNk7SBY0BcjkU=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "a684c58d46ebbede49f280b653b9e56100aa3877",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-24.11",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
     "root": {
       "inputs": {
         "flake-parts": "flake-parts",
         "lean4-nix": "lean4-nix",
-        "nixpkgs": "nixpkgs"
+        "nixpkgs": "nixpkgs_2"
       }
     }
   },

flake.nix

@@ -4,10 +4,7 @@
   inputs = {
     nixpkgs.url = "github:nixos/nixpkgs/nixos-24.11";
     flake-parts.url = "github:hercules-ci/flake-parts";
-    lean4-nix = {
-      url = "github:lenianiva/lean4-nix";
-      inputs.nixpkgs.follows = "nixpkgs";
-    };
+    lean4-nix.url = "github:lenianiva/lean4-nix";
   };
 
   outputs = inputs @ {

lean-toolchain

@@ -1 +1 @@
-leanprover/lean4:v4.20.1
+leanprover/lean4:v4.21.0