From 38b51d5b7ef1655add0dedf3efb8ae013dc80236 Mon Sep 17 00:00:00 2001
From: Charles Schlosser <cs.schlosser@gmail.com>
Date: Tue, 26 Aug 2025 20:04:17 +0000
Subject: [PATCH] Mitigate setConstant regression with custom scalars

---
 Eigen/src/Core/Fill.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Eigen/src/Core/Fill.h b/Eigen/src/Core/Fill.h
index 9d4ecd445..f40d56db6 100644
--- a/Eigen/src/Core/Fill.h
+++ b/Eigen/src/Core/Fill.h
@@ -78,8 +78,9 @@ template <typename Xpr>
 struct eigen_fill_impl<Xpr, /*use_fill*/ true> {
   using Scalar = typename Xpr::Scalar;
   static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void run(Xpr& dst, const Scalar& val) {
+    const Scalar val_copy = val;
     using std::fill_n;
-    fill_n(dst.data(), dst.size(), val);
+    fill_n(dst.data(), dst.size(), val_copy);
   }
   template <typename SrcXpr>
   static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void run(Xpr& dst, const SrcXpr& src) {