From cbdd358ae845b8295a85d416a22c93f64a48cd03 Mon Sep 17 00:00:00 2001
From: Jonathan G Rennison <j.g.rennison@gmail.com>
Date: Sat, 19 Jul 2025 10:32:09 +0100
Subject: [PATCH] Codechange: Allow SmallStack Titem type to be non-structural

---
 src/core/smallstack_type.hpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/core/smallstack_type.hpp b/src/core/smallstack_type.hpp
index 1a88f0df1a..3b26951453 100644
--- a/src/core/smallstack_type.hpp
+++ b/src/core/smallstack_type.hpp
@@ -113,13 +113,14 @@ struct SmallStackItem {
  *    index types of the same length.
  * @tparam Titem Value type to be used.
  * @tparam Tindex Index type to use for the pool.
- * @tparam Tinvalid Invalid item to keep at the bottom of each stack.
+ * @tparam Tinvalid_value Value to construct invalid item to keep at the bottom of each stack.
  * @tparam Tgrowth_step Growth step for pool.
  * @tparam Tmax_size Maximum size for pool.
  */
-template <typename Titem, typename Tindex, Titem Tinvalid, Tindex Tgrowth_step, Tindex Tmax_size>
+template <typename Titem, typename Tindex, auto Tinvalid_value, Tindex Tgrowth_step, Tindex Tmax_size>
 class SmallStack : public SmallStackItem<Titem, Tindex> {
 public:
+	static constexpr Titem Tinvalid{Tinvalid_value};
 
 	typedef SmallStackItem<Titem, Tindex> Item;