callHackage: generate expressions for the appropriate target system and compiler

pkgs/development/haskell-modules/default.nix

···
 
 let
 
-  inherit (stdenv.lib) fix' extends;
+  allCabalFiles = pkgs.fetchFromGitHub {
+     owner = "commercialhaskell";
+     repo = "all-cabal-hashes";
+     rev = "461610ab6f0cf581e186643c037f1981755792d9";
+     sha256 = "0x2577lfd5cbbaivl72273kw93gcmxvbjybk7w4h2ic3zvs1fnvm";
+   };
 
-  inherit (import ./lib.nix { inherit pkgs; }) hackage2nix;
+  inherit (stdenv.lib) fix' extends;
 
   haskellPackages = self:
     let
···
         inherit (self) llvmPackages;
         haskellPackages = self;
         inherit packages;
+      };
+
+      hackage2nix = name: version: pkgs.stdenv.mkDerivation {
+        name = "cabal2nix-${name}-${version}";
+        buildInputs = [ pkgs.cabal2nix ];
+        phases = ["installPhase"];
+        LANG = "en_US.UTF-8";
+        LOCALE_ARCHIVE = pkgs.lib.optionalString pkgs.stdenv.isLinux "${pkgs.glibcLocales}/lib/locale/locale-archive";
+        installPhase = ''
+          export HOME="$TMP"
+          mkdir $out
+          hash=$(sed -e 's/.*"SHA256":"//' -e 's/".*$//' ${allCabalFiles}/${name}/${version}/${name}.json)
+          cabal2nix --compiler=${self.ghc.name} --system=${stdenv.system} --sha256=$hash ${allCabalFiles}/${name}/${version}/${name}.cabal >$out/default.nix
+        '';
       };
 
     in

pkgs/development/haskell-modules/lib.nix

···
 
   triggerRebuild = drv: i: overrideCabal drv (drv: { postUnpack = ": trigger rebuild ${toString i}"; });
 
-  allCabalFiles = pkgs.fetchFromGitHub {
-     owner = "commercialhaskell";
-     repo = "all-cabal-hashes";
-     rev = "461610ab6f0cf581e186643c037f1981755792d9";
-     sha256 = "0x2577lfd5cbbaivl72273kw93gcmxvbjybk7w4h2ic3zvs1fnvm";
-   };
-
-   hackage2nix = name: version: pkgs.stdenv.mkDerivation {
-     name = "cabal2nix-${name}-${version}";
-     buildInputs = [ pkgs.cabal2nix ];
-     phases = ["installPhase"];
-     LANG = "en_US.UTF-8";
-     LOCALE_ARCHIVE = pkgs.lib.optionalString pkgs.stdenv.isLinux "${pkgs.glibcLocales}/lib/locale/locale-archive";
-     installPhase = ''
-       export HOME="$TMP"
-       mkdir $out
-       hash=$(sed -e 's/.*"SHA256":"//' -e 's/".*$//' ${allCabalFiles}/${name}/${version}/${name}.json)
-       cabal2nix --sha256=$hash ${allCabalFiles}/${name}/${version}/${name}.cabal >$out/default.nix
-     '';
-   };
-
 }