From 96dbdd6a9ec709290e822d3e8f15e628c1f415dd Mon Sep 17 00:00:00 2001
From: Eman Resu <78693624+quatquatt@users.noreply.github.com>
Date: Sun, 7 Jun 2026 16:28:24 -0400
Subject: [PATCH] lib.modules: inline `head defs` variable

Each value passed to a function or primop is passed as a thunk, so `head
defs` will only be evaluated twice if we're throwing an error. Validated
with `builtins.trace`.
---
 lib/modules.nix | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/lib/modules.nix b/lib/modules.nix
index f953b9e62a68..a84ffd2d9aa6 100644
--- a/lib/modules.nix
+++ b/lib/modules.nix
@@ -1193,11 +1193,8 @@ let
       # original singleton straight to the type merge.
       if
         length defs == 1
-        && (
-          let
-            d = head defs;
-          in
-          addErrorContext "while evaluating definitions from `${d.file}':" (!d.value ? _type)
+        && addErrorContext "while evaluating definitions from `${(head defs).file}':" (
+          !(head defs).value ? _type
         )
       then
         {