From ac8670236f723ea4406f26ee75849e515f8a0d36 Mon Sep 17 00:00:00 2001
From: Johannes Kirschbauer <hsjobeki@gmail.com>
Date: Sun, 24 Nov 2024 17:47:41 +0100
Subject: [PATCH] lib.types.defaultTypeMerge: add 'loc' to default type merge

---
 lib/modules.nix | 3 ++-
 lib/types.nix   | 6 ++++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/lib/modules.nix b/lib/modules.nix
index 855ffaf25ed81..08d15804daedb 100644
--- a/lib/modules.nix
+++ b/lib/modules.nix
@@ -11,6 +11,7 @@ let
     concatLists
     concatMap
     concatStringsSep
+    defaultTypeMerge
     elem
     filter
     foldl'
@@ -749,7 +750,7 @@ let
     foldl' (res: opt:
       let t  = res.type;
           t' = opt.options.type;
-          mergedType = t.typeMerge t'.functor;
+          mergedType = defaultTypeMerge loc t.functor t'.functor;
           typesMergeable = mergedType != null;
           typeSet = if (bothHave "type") && typesMergeable
                        then { type = mergedType; }
diff --git a/lib/types.nix b/lib/types.nix
index 82d7425ca6439..5655fc598a814 100644
--- a/lib/types.nix
+++ b/lib/types.nix
@@ -82,7 +82,7 @@ rec {
 
   # Default type merging function
   # takes two type functors and return the merged type
-  defaultTypeMerge = f: f':
+  defaultTypeMerge = loc: f: f':
     let mergedWrapped = f.wrapped.typeMerge f'.wrapped.functor;
         mergedPayload = f.binOp f.payload f'.payload;
 
@@ -103,6 +103,8 @@ rec {
           Use either `functor.payload` or `functor.wrapped` but not both.
 
           If your code worked before remove `functor.payload` from the type definition.
+
+          Location: ${showOption loc}
         ''
       else
         # Has payload
@@ -182,7 +184,7 @@ rec {
     , # Function that merge type declarations.
       # internal, takes a functor as argument and returns the merged type.
       # returning null means the type is not mergeable
-      typeMerge ? defaultTypeMerge functor
+      typeMerge ? defaultTypeMerge ["unknown location"] functor
     , # The type functor.
       # internal, representation of the type as an attribute set.
       #   name: name of the type