feat(nix): replace fenix with rust-overlay

We're going to use rust-overlay for setting up an MSRV build.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

2 files changed, 24 insertions, 38 deletions

diff --git a/flake.lock b/flake.lock
index d8a0ace7..c8ea8d15 100644
--- a/flake.lock
+++ b/flake.lock
@@ -15,27 +15,6 @@
         "type": "github"
       }
     },
-    "fenix": {
-      "inputs": {
-        "nixpkgs": [
-          "nixpkgs"
-        ],
-        "rust-analyzer-src": "rust-analyzer-src"
-      },
-      "locked": {
-        "lastModified": 1742452566,
-        "narHash": "sha256-sVuLDQ2UIWfXUBbctzrZrXM2X05YjX08K7XHMztt36E=",
-        "owner": "nix-community",
-        "repo": "fenix",
-        "rev": "7d9ba794daf5e8cc7ee728859bc688d8e26d5f06",
-        "type": "github"
-      },
-      "original": {
-        "owner": "nix-community",
-        "repo": "fenix",
-        "type": "github"
-      }
-    },
     "flake-compat": {
       "flake": false,
       "locked": {
@@ -104,27 +83,30 @@
     "root": {
       "inputs": {
         "crane": "crane",
-        "fenix": "fenix",
         "flake-compat": "flake-compat",
         "flake-parts": "flake-parts",
         "nixpkgs": "nixpkgs",
+        "rust-overlay": "rust-overlay",
         "treefmt-nix": "treefmt-nix"
       }
     },
-    "rust-analyzer-src": {
-      "flake": false,
+    "rust-overlay": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
       "locked": {
-        "lastModified": 1742296961,
-        "narHash": "sha256-gCpvEQOrugHWLimD1wTFOJHagnSEP6VYBDspq96Idu0=",
-        "owner": "rust-lang",
-        "repo": "rust-analyzer",
-        "rev": "15d87419f1a123d8f888d608129c3ce3ff8f13d4",
+        "lastModified": 1742524367,
+        "narHash": "sha256-KzTwk/5ETJavJZYV1DEWdCx05M4duFCxCpRbQSKWpng=",
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "rev": "70bf752d176b2ce07417e346d85486acea9040ef",
         "type": "github"
       },
       "original": {
-        "owner": "rust-lang",
-        "ref": "nightly",
-        "repo": "rust-analyzer",
+        "owner": "oxalica",
+        "repo": "rust-overlay",
         "type": "github"
       }
     },
diff --git a/flake.nix b/flake.nix
index 9e09a621..5f93f522 100644
--- a/flake.nix
+++ b/flake.nix
@@ -13,8 +13,8 @@
 
     crane.url = "github:ipetkov/crane";
 
-    fenix = {
-      url = "github:nix-community/fenix";
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
       inputs.nixpkgs.follows = "nixpkgs";
     };
 
@@ -30,9 +30,9 @@
       nixpkgs,
       flake-parts,
       treefmt-nix,
-      fenix,
       crane,
-      ...
+      rust-overlay,
+      flake-compat,
     }:
     let
       systems = nixpkgs.lib.filter (s: nixpkgs.lib.hasSuffix "-linux" s) nixpkgs.lib.systems.flakeExposed;
@@ -47,7 +47,6 @@
           self',
           config,
           lib,
-          pkgs,
           system,
           ...
         }:
@@ -56,6 +55,11 @@
           inherit (lib.lists) findFirst;
           inherit (lib.strings) hasPrefix removePrefix substring;
 
+          pkgs = import nixpkgs {
+            inherit system;
+            overlays = [ (import rust-overlay) ];
+          };
+
           cargoToml = builtins.fromTOML (builtins.readFile ./Cargo.toml);
           rustfmtToml = builtins.fromTOML (builtins.readFile ./rustfmt.toml);
 
@@ -198,7 +202,7 @@
               nixfmt.enable = true;
               rustfmt.edition = rustfmtToml.edition;
               rustfmt.enable = true;
-              rustfmt.package = fenix.packages.${system}.default.rustfmt;
+              rustfmt.package = pkgs.rust-bin.selectLatestNightlyWith (toolchain: toolchain.rustfmt);
             };
           };
         };