From 449624f910b5081de9d93d98209b862d5d42b5e1 Mon Sep 17 00:00:00 2001
From: Valentin Balaschenko <13349202+vlntb@users.noreply.github.com>
Date: Tue, 7 Jul 2026 13:13:41 +0100
Subject: [PATCH] added static_assert to prevent future misuse

---
 include/xrpl/basics/TaggedCache.ipp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/xrpl/basics/TaggedCache.ipp b/include/xrpl/basics/TaggedCache.ipp
index af3fff04a9..972c5c5289 100644
--- a/include/xrpl/basics/TaggedCache.ipp
+++ b/include/xrpl/basics/TaggedCache.ipp
@@ -663,6 +663,9 @@ TaggedCache<Key, T, IsKeyCache, SharedWeakUnionPointer, SharedPointerType, Hash,
 {
     static_assert(
         !IsKeyCache, "fetchAndModify is only supported for value caches, not key-only caches");
+    static_assert(
+        std::is_same_v<Mutex, std::recursive_mutex>,
+        "fetchAndModify requires a recursive mutex because canonicalize re-acquires mutex_ internally");
 
     std::scoped_lock const lock(mutex_);