fix: use toolchain declared in rust-toolchain.toml for cross rust-std

nix/packages/default.nix

@@ -9,8 +9,10 @@
       self',
       lib,
       pkgs,
+      inputs',
       system,
       craneLib,
+      mkToolchain,
       ...
     }:
     {
@@ -19,7 +21,7 @@
           mkPackages =
             pkgs:
             let
-              fnx = inputs.fenix.packages.${system};
+              fnx = inputs'.fenix.packages;
 
               isStatic = pkgs.stdenv.hostPlatform.isMusl;
 
@@ -28,7 +30,7 @@
                 if isStatic then
                   fnx.combine [
                     self'.packages.stable-toolchain
-                    (fnx.targets.${pkgs.stdenv.hostPlatform.config}.stable).rust-std
+                    (mkToolchain fnx.targets.${pkgs.stdenv.hostPlatform.config}).rust-std
                   ]
                 else
                   self'.packages.stable-toolchain
@@ -62,7 +64,6 @@
             in
             {
               inherit default max-perf max-perf-haswell;
-
             };
         in
         {

nix/rust.nix

@@ -2,22 +2,26 @@
 {
   perSystem =
     {
-      system,
       lib,
+      inputs',
       pkgs,
       ...
     }:
+    let
+      mkToolchain =
+        target:
+        target.fromToolchainName {
+          name = (lib.importTOML "${inputs.self}/rust-toolchain.toml").toolchain.channel;
+          sha256 = "sha256-mvUGEOHYJpn3ikC5hckneuGixaC+yGrkMM/liDIDgoU=";
+        };
+    in
     {
+      _module.args = { inherit mkToolchain; };
+
       packages =
         let
-          fnx = inputs.fenix.packages.${system};
-
-          stable-toolchain = fnx.fromToolchainFile {
-            dir = inputs.self;
-
-            # See also `rust-toolchain.toml`
-            sha256 = "sha256-mvUGEOHYJpn3ikC5hckneuGixaC+yGrkMM/liDIDgoU=";
-          };
+          fnx = inputs'.fenix.packages;
+          stable-toolchain = (mkToolchain fnx).toolchain;
         in
         {
           inherit stable-toolchain;