ghc-exactprint: init at upstream GHC 9.4 branch

flake.nix

@@ -42,6 +42,10 @@
     };
     flake-parts.url = "github:hercules-ci/flake-parts";
     flake-parts.inputs.nixpkgs.follows = "nixpkgs";
+    ghc-exactprint = {
+      url = "github:alanz/ghc-exactprint?ref=ghc-9.4";
+      flake = false;
+    };
     haskell-src-meta = {
       url = "github:parsonsmatt/haskell-src-meta?ref=matt/support-new-th";
       flake = false;

overlay.nix

@@ -149,6 +149,8 @@ final: prev: with pkgs.haskell.lib; {
 
   ghc-byteorder = doJailbreak (prev.callHackage "ghc-byteorder" "4.11.0.0.10" { });
 
+  ghc-exactprint = prev.callCabal2nix "ghc-exactprint" inputs.ghc-exactprint { };
+
   ghc-lib-parser = doJailbreak (prev.callHackage "ghc-lib-parser" "9.4.2.20220822" { });
 
   ghc-lib-parser-ex = doJailbreak (prev.callHackage "ghc-lib-parser-ex" "9.4.0.0" { });