test on OCaml 5.2, improve nix flake

.github/workflows/test.yml

@@ -9,12 +9,12 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ocamlVersion: [4_14, 5_0, 5_1]
+        ocamlVersion: [4_14, 5_1, 5_2]
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
       with:
         submodules: 'recursive'
-    - uses: cachix/install-nix-action@v20
+    - uses: cachix/install-nix-action@v27
       with:
         extra_nix_config: |
           extra-substituters = https://anmonteiro.nix-cache.workers.dev

flake.nix

@@ -12,13 +12,14 @@
         pkgs = nixpkgs.legacyPackages."${system}".extend (self: super: {
           ocamlPackages = super.ocaml-ng.ocamlPackages_5_2;
         });
-      in
-      rec {
         packages = pkgs.callPackage ./nix { nix-filter = nix-filter.lib; };
+      in
+      {
+        packages = packages // { default = packages.h2; };
         defaultPackage = packages.h2;
-        devShells = rec {
+        devShells = {
           default = pkgs.callPackage ./nix/shell.nix { inherit packages; };
-          release = default.override { release-mode = true; };
+          release = self.devShells.${system}.default.override { release-mode = true; };
         };
       });
 }

hpack/util/dune

@@ -1,3 +1,9 @@
-(executables
- (names gen_huffman gen_static)
+(executable
+ (name gen_huffman)
  (libraries compiler-libs.common))
+
+(executable
+ (name gen_static)
+ (libraries compiler-libs.common)
+ (enabled_if
+  (< %{ocaml_version} 5.2)))