From 208981d85889981286060dc1fffad826ab356562 Mon Sep 17 00:00:00 2001
From: Bruno Turcksin <bruno.turcksin@gmail.com>
Date: Mon, 28 Oct 2024 11:16:32 -0400
Subject: [PATCH] Fix C++20 Tensor initialization

---
 include/deal.II/base/tensor.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/deal.II/base/tensor.h b/include/deal.II/base/tensor.h
index 40ba24ba1c..b7f2c0e530 100644
--- a/include/deal.II/base/tensor.h
+++ b/include/deal.II/base/tensor.h
@@ -1292,7 +1292,11 @@ Tensor<rank_, dim, Number>::Tensor()
       // returning a zero instead.
       []<std::size_t... I>(
         const std::index_sequence<I...> &) constexpr -> decltype(values) {
-        if constexpr (rank_ == 1)
+        if constexpr (dim == 0)
+          {
+            return {};
+          }
+        else if constexpr (rank_ == 1)
           {
             auto get_zero_and_ignore_argument = [](int) {
               return internal::NumberType<Number>::value(0.0);
-- 
2.39.5