nix: Override haskellPackages.Agda

Author: HeinrichApfelmus

flake.nix

@@ -13,7 +13,23 @@
     flake-utils.lib.eachDefaultSystem (
       system:
       let
-        pkgs = import nixpkgs { inherit system; };
+        pkgver = "Agda-2.7.20250601";
+        sha256 = "sha256-ng/ijIIdiJqGrlqTt36rpO38XHFRuvhDUr0Z58P7eaw=";
+        overlayHaskellPackages = self: super: {
+          haskellPackages = super.haskellPackages.override {
+            overrides = self: super: {
+              Agda = self.callCabal2nix "Agda" (pkgs.fetchzip {
+                url = "mirror://hackage/${pkgver}/candidate/${pkgver}.tar.gz";
+                inherit sha256;
+              }) {};
+            };
+          };
+        };
+
+        pkgs = import nixpkgs {
+          inherit system;
+          overlays = [ overlayHaskellPackages ];
+        };
         packages = import ./nix/default.nix { inherit pkgs; };
         lib = import ./nix/lib.nix { inherit pkgs; };
       in