From 413f4666cdd4813f34de17b174c7f93dd573ec41 Mon Sep 17 00:00:00 2001
From: dramforever <dramforever@live.com>
Date: Sun, 22 Mar 2026 13:49:52 +0800
Subject: [PATCH 1/2] lib/modules: Improve errors involving pushDownProperties

If an attrset option was given a definition like:

    { system = lib.mkIf true false; }

Before this change, we get the non-explanatory error message:

    error: expected a set but found a Boolean: true

With the stack trace having nothing to do with the module involved.
After this change, we get the better:

    error: In module `[...]', you're trying to define a value of type `bool' [...]

Which names the actual module involved.
---
 lib/modules.nix | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/lib/modules.nix b/lib/modules.nix
index c67ea2247ca7..054f18a004f3 100644
--- a/lib/modules.nix
+++ b/lib/modules.nix
@@ -1320,13 +1320,24 @@ let
     : 1\. Function argument
   */
   pushDownProperties =
+    let
+      mapAttrsIfAttrs =
+        f: val:
+        if isAttrs val then
+          mapAttrs f val
+        else
+          # This does not actually work, since arriving here means we have e.g.
+          # (lib.mkIf cond nonAttrs), while an attrset is expected. However,
+          # avoiding the mapAttrs call here gives better errors later.
+          val;
+    in
     cfg:
     if cfg._type or "" == "merge" then
       concatMap pushDownProperties cfg.contents
     else if cfg._type or "" == "if" then
-      map (mapAttrs (n: v: mkIf cfg.condition v)) (pushDownProperties cfg.content)
+      map (mapAttrsIfAttrs (n: v: mkIf cfg.condition v)) (pushDownProperties cfg.content)
     else if cfg._type or "" == "override" then
-      map (mapAttrs (n: v: mkOverride cfg.priority v)) (pushDownProperties cfg.content)
+      map (mapAttrsIfAttrs (n: v: mkOverride cfg.priority v)) (pushDownProperties cfg.content)
     # FIXME: handle mkOrder?
     else
       [ cfg ];

From d48a370de11ccfd407d12ee3f15ac6e7ceedc5cc Mon Sep 17 00:00:00 2001
From: dramforever <dramforever@live.com>
Date: Sun, 22 Mar 2026 14:11:01 +0800
Subject: [PATCH 2/2] lib/modules: Add error message test for pushing down
 non-attrsets

---
 lib/tests/modules.sh                           | 2 ++
 lib/tests/modules/test-push-down-non-attrs.nix | 5 +++++
 2 files changed, 7 insertions(+)
 create mode 100644 lib/tests/modules/test-push-down-non-attrs.nix

diff --git a/lib/tests/modules.sh b/lib/tests/modules.sh
index aa9d3443fb6a..bf309a604f26 100755
--- a/lib/tests/modules.sh
+++ b/lib/tests/modules.sh
@@ -171,6 +171,8 @@ checkConfigError() {
 # Shorthand meta attribute does not duplicate the config
 checkConfigOutput '^"one two"$' config.result ./shorthand-meta.nix
 
+checkConfigError "In module .*test-push-down-non-attrs.nix., you're trying to define a value of type \`bool'\n\s*rather than an attribute set for the option" config ./test-push-down-non-attrs.nix
+
 checkConfigOutput '^true$' config.result ./test-mergeAttrDefinitionsWithPrio.nix
 
 # Check that a module argument is passed, also when a default is available
diff --git a/lib/tests/modules/test-push-down-non-attrs.nix b/lib/tests/modules/test-push-down-non-attrs.nix
new file mode 100644
index 000000000000..ce9222ca3cfd
--- /dev/null
+++ b/lib/tests/modules/test-push-down-non-attrs.nix
@@ -0,0 +1,5 @@
+{ lib, ... }:
+
+{
+  config = lib.mkIf true true;
+}