Mark some 'constexpr' as 'inline'.

diff --git a/include/deal.II/base/template_constraints.h b/include/deal.II/base/template_constraints.h
index 7d635356aa98df016291c6fe2a82bcde805d96d1..0553bf6cd1e6d9efe6a656d4fc749a2d24ba1495 100644 (file)
--- a/include/deal.II/base/template_constraints.h
+++ b/include/deal.II/base/template_constraints.h
@@ -907,34 +907,34 @@ namespace parallel
 
 namespace concepts
 {
+#if defined(DEAL_II_HAVE_CXX20) || defined(DOXYGEN)
   namespace internal
   {
     template <typename T>
-    constexpr bool is_triangulation_or_dof_handler = false;
+    inline constexpr bool is_triangulation_or_dof_handler = false;
 
     template <int dim, int spacedim>
-    constexpr bool
+    inline constexpr bool
       is_triangulation_or_dof_handler<Triangulation<dim, spacedim>> = true;
 
     template <int dim, int spacedim>
-    constexpr bool is_triangulation_or_dof_handler<
+    inline constexpr bool is_triangulation_or_dof_handler<
       parallel::distributed::Triangulation<dim, spacedim>> = true;
 
     template <int dim, int spacedim>
-    constexpr bool is_triangulation_or_dof_handler<
+    inline constexpr bool is_triangulation_or_dof_handler<
       parallel::shared::Triangulation<dim, spacedim>> = true;
 
     template <int dim, int spacedim>
-    constexpr bool is_triangulation_or_dof_handler<
+    inline constexpr bool is_triangulation_or_dof_handler<
       parallel::fullydistributed::Triangulation<dim, spacedim>> = true;
 
     template <int dim, int spacedim>
-    constexpr bool is_triangulation_or_dof_handler<DoFHandler<dim, spacedim>> =
-      true;
+    inline constexpr bool
+      is_triangulation_or_dof_handler<DoFHandler<dim, spacedim>> = true;
   } // namespace internal
 
 
-#if defined(DEAL_II_HAVE_CXX20) || defined(DOXYGEN)
   /**
    * A concept that is used to check whether the `MeshType` template
    * type used in many functions in namespace GridTools and