From b58efb6b0f50d4fe03cb48426b79a08b93d3017a Mon Sep 17 00:00:00 2001
From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Wed, 14 Aug 2024 10:18:02 -0600
Subject: [PATCH] Improve an error message.

---
 source/fe/fe_system.cc | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/source/fe/fe_system.cc b/source/fe/fe_system.cc
index 8a4bcc7aca..a54f8cf290 100644
--- a/source/fe/fe_system.cc
+++ b/source/fe/fe_system.cc
@@ -2422,7 +2422,14 @@ FESystem<dim, spacedim>::compare_for_domination(
         dynamic_cast<const FESystem<dim, spacedim> *>(&fe_other))
     {
       Assert(this->n_components() == fe_sys_other->n_components(),
-             ExcNotImplemented());
+             ExcMessage("You can only compare two elements for domination "
+                        "that have the same number of vector components. The "
+                        "current element has " +
+                        std::to_string(this->n_components()) +
+                        " vector components, and you are comparing it "
+                        "against an element with " +
+                        std::to_string(fe_sys_other->n_components()) +
+                        " vector components."));
       Assert(this->n_base_elements() == fe_sys_other->n_base_elements(),
              ExcNotImplemented());
 
-- 
2.39.5