Add `constexpr` to type check.

diff --git a/include/deal.II/base/utilities.h b/include/deal.II/base/utilities.h
index 2d3b81b6f0013f4714a7fdc5aa69d33bbe0681c3..0643eec0c26ff26fb1f6499b78a970433c3c75fc 100644 (file)
--- a/include/deal.II/base/utilities.h
+++ b/include/deal.II/base/utilities.h
@@ -1334,7 +1334,11 @@ namespace Utilities
     // see if the object is small and copyable via memcpy. if so, use
     // this fast path. otherwise, we have to go through the BOOST
     // serialization machinery
+#ifdef DEAL_II_HAVE_CXX17
+    if constexpr (std::is_trivially_copyable<T>() && sizeof(T) * N < 256)
+#else
     if (std::is_trivially_copyable<T>() && sizeof(T) * N < 256)
+#endif
       {
         Assert(std::distance(cbegin, cend) == sizeof(T) * N,
                ExcInternalError());