From 8b9dbcdaaf668d39ace2757f5d91860036a8e738 Mon Sep 17 00:00:00 2001
From: Tyler Veness <calcmogul@gmail.com>
Date: Thu, 7 Aug 2025 00:03:33 +0000
Subject: [PATCH] Fix numext::bit_cast() compilation failure in C++20

---
 Eigen/src/Core/NumTraits.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/Eigen/src/Core/NumTraits.h b/Eigen/src/Core/NumTraits.h
index b93faae26..bf41c3bb6 100644
--- a/Eigen/src/Core/NumTraits.h
+++ b/Eigen/src/Core/NumTraits.h
@@ -98,7 +98,10 @@ namespace numext {
 
 /** \internal bit-wise cast without changing the underlying bit representation. */
 #if defined(__cpp_lib_bit_cast) && __cpp_lib_bit_cast >= 201806L
-EIGEN_STRONG_INLINE EIGEN_DEVICE_FUNC constexpr Tgt bit_cast(const Src& src) { return std::bit_cast<Tgt>(src); }
+template <typename Tgt, typename Src>
+EIGEN_STRONG_INLINE EIGEN_DEVICE_FUNC constexpr Tgt bit_cast(const Src& src) {
+  return std::bit_cast<Tgt>(src);
+}
 #elif EIGEN_HAS_BUILTIN(__builtin_bit_cast)
 template <typename Tgt, typename Src>
 EIGEN_STRONG_INLINE EIGEN_DEVICE_FUNC constexpr Tgt bit_cast(const Src& src) {