From 8bc78cf9baf1adaef1060d3b3376dc35ed15d0e9 Mon Sep 17 00:00:00 2001
From: Pablo Lamela <pablo.lamela@iohk.io>
Date: Wed, 1 Apr 2026 01:45:52 +0200
Subject: [PATCH] Add `ghc914` dev shell for `x86_64-linux` and make haddock
 build in CI use it

---
 .github/workflows/github-page.yml |  2 ++
 flake.nix                         | 15 +++++++++++----
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/.github/workflows/github-page.yml b/.github/workflows/github-page.yml
index 3002f776f5..d9e3f3e764 100644
--- a/.github/workflows/github-page.yml
+++ b/.github/workflows/github-page.yml
@@ -25,6 +25,8 @@ jobs:
             substituters = https://cache.iog.io/ https://cache.nixos.org/
 
       - uses: rrbutani/use-nix-shell-action@v1
+        with:
+          devShell: .#ghc914
 
       - name: Update cabal indices
         run: |
diff --git a/flake.nix b/flake.nix
index f7cd3f5d19..43be3484b8 100644
--- a/flake.nix
+++ b/flake.nix
@@ -55,6 +55,8 @@
     defaultCompiler = "ghc9122";
     # Used for cross compilation for windows.
     crossCompilerVersion = defaultCompiler;
+    # Used for haddock generation (avoids GHC 9.12 tyConStupidTheta panic)
+    haddockCompiler = "ghc914";
   in
     inputs.flake-utils.lib.eachSystem supportedSystems (
       system: let
@@ -226,7 +228,11 @@
             # TODO remove this module when removing proto-lens SRP
             # Override proto-lens source to use fixed symlinks (inputMap provides the fixed
             # source for plan computation; this module provides it for the build phase)
-            ({lib, config, ...}: let
+            ({
+              lib,
+              config,
+              ...
+            }: let
               protoLensPackages = [
                 "proto-lens"
                 "proto-lens-arbitrary"
@@ -242,9 +248,10 @@
                 "proto-lens-benchmarks"
               ];
             in {
-              packages = lib.genAttrs
+              packages =
+                lib.genAttrs
                 (builtins.filter (p: config.packages ? ${p}) protoLensPackages)
-                (p: { src = lib.mkForce (fixProtoLensSrc + "/${p}"); });
+                (p: {src = lib.mkForce (fixProtoLensSrc + "/${p}");});
             })
             ({...}: {
               packages.cardano-api = {
@@ -306,7 +313,7 @@
                 then defaultCompiler
                 else stableCompiler;
             in
-              lib.genAttrs [osDependentStableCompiler crossCompilerVersion] (compiler-nix-name: {
+              lib.genAttrs [osDependentStableCompiler crossCompilerVersion haddockCompiler] (compiler-nix-name: {
                 inherit compiler-nix-name;
               });
           }