feat(nix): switch to provisioning toolchains using fenix

rust-overlay's `fromRustupToolchainFile` does not provision the provided
components from the `rust-toolchain.toml` file which makes the experience
subpar compared to fenix that treats `rust-toolchain.toml` similar to rustup.

flake.lock

@@ -27,9 +27,7 @@
         "nixpkgs": [
           "nixpkgs"
         ],
-        "rust-overlay": [
+        "rust-overlay": "rust-overlay"
-          "rust-overlay"
-        ]
       },
       "locked": {
         "lastModified": 1683505101,
@@ -45,6 +43,27 @@
         "type": "github"
       }
     },
+    "fenix": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ],
+        "rust-analyzer-src": "rust-analyzer-src"
+      },
+      "locked": {
+        "lastModified": 1684045209,
+        "narHash": "sha256-d6WRNsb5+P7wocC/wCMjkvF0pycKuZ7SHgj5NGmESNQ=",
+        "owner": "nix-community",
+        "repo": "fenix",
+        "rev": "7c8be7e3312ba06dc95491a44c3c9ba71a175bc4",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "repo": "fenix",
+        "type": "github"
+      }
+    },
     "flake-compat": {
       "flake": false,
       "locked": {
@@ -99,27 +118,46 @@
       "inputs": {
         "advisory-db": "advisory-db",
         "crane": "crane",
+        "fenix": "fenix",
         "flake-compat": "flake-compat",
         "flake-utils": "flake-utils",
-        "nixpkgs": "nixpkgs",
+        "nixpkgs": "nixpkgs"
-        "rust-overlay": "rust-overlay"
+      }
+    },
+    "rust-analyzer-src": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1684005690,
+        "narHash": "sha256-m0Dya15vVk4swQdWKqDYHmdU3cirySRjaQ6EgMa2Mcg=",
+        "owner": "rust-lang",
+        "repo": "rust-analyzer",
+        "rev": "cbd14e98403dc5e19f19fdf913808656d81a0516",
+        "type": "github"
+      },
+      "original": {
+        "owner": "rust-lang",
+        "ref": "nightly",
+        "repo": "rust-analyzer",
+        "type": "github"
       }
     },
     "rust-overlay": {
       "inputs": {
         "flake-utils": [
+          "crane",
           "flake-utils"
         ],
         "nixpkgs": [
+          "crane",
           "nixpkgs"
         ]
       },
       "locked": {
-        "lastModified": 1684030847,
+        "lastModified": 1684117262,
-        "narHash": "sha256-z4tOxaN9Cl8C80u6wyZBpPt9A9MbL21fZ3zdB/vG+AU=",
+        "narHash": "sha256-ZSF4CZqeyk6QwTjal73KPMuTWiU6w/p8ygEimrPb7u4=",
         "owner": "oxalica",
         "repo": "rust-overlay",
-        "rev": "aa1480f16bec7dda3c62b8cdb184c7e823331ba2",
+        "rev": "4679872d2dd3e94ffef75efcbf77ea11549d90a7",
         "type": "github"
       },
       "original": {

flake.nix

@@ -4,6 +4,13 @@
   inputs = {
     nixpkgs = {url = "github:NixOS/nixpkgs/nixpkgs-unstable";};
 
+    fenix = {
+      url = "github:nix-community/fenix";
+      inputs = {
+        nixpkgs.follows = "nixpkgs";
+      };
+    };
+
     flake-utils = {url = "github:numtide/flake-utils";};
 
     flake-compat = {
@@ -11,21 +18,12 @@
       flake = false;
     };
 
-    rust-overlay = {
-      url = "github:oxalica/rust-overlay";
-      inputs = {
-        nixpkgs.follows = "nixpkgs";
-        flake-utils.follows = "flake-utils";
-      };
-    };
-
     crane = {
       url = "github:ipetkov/crane";
       inputs = {
         flake-compat.follows = "flake-compat";
         flake-utils.follows = "flake-utils";
         nixpkgs.follows = "nixpkgs";
-        rust-overlay.follows = "rust-overlay";
       };
     };
 
@@ -38,20 +36,20 @@
   outputs = {
     self,
     nixpkgs,
+    fenix,
     crane,
     flake-utils,
     advisory-db,
-    rust-overlay,
     ...
   }:
     flake-utils.lib.eachDefaultSystem (system: let
-      pkgs = import nixpkgs {
+      pkgs = import nixpkgs {inherit system;};
-        inherit system;
+
-        overlays = [(import rust-overlay)];
+      rustStable = (import fenix {inherit pkgs;}).fromToolchainFile {
+        file = ./rust-toolchain.toml;
+        sha256 = "sha256-1elQHBWEQRZ5qrEtJi6uhvwUNKedyQusyhATdBywep0=";
       };
 
-      rustStable =
-        pkgs.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
       craneLib = (crane.mkLib pkgs).overrideToolchain rustStable;
       src = craneLib.cleanCargoSource ./.;
       nativeBuildInputs = [];