Concatenated namespaces require C++17, but we still support C++11.
@@ -29,6 +29,7 @@ misc-*,\
-misc-use-internal-linkage,\
modernize-*,\
-modernize-avoid-c-arrays,\
+-modernize-concat-nested-namespaces,\
-modernize-macro-to-enum,\
-modernize-return-braced-init-list,\
-modernize-type-traits,\
Brad King