Unnamed namespaces should not be nested within each other

Very similar to https://rules.sonarsource.com/cpp/RSPEC-3609 When you already inside an unnamed namespace, opening another unnamed namespace is redundant.

namespace { // Outer namespace begin
namespace { // Redundant namespace
} // Redundant namespae end
} // Outer namespace end

Hello @torgeir.skogen.

Thanks for this other interesting idea. I’ve raised [CPP-4026] - Jira for this purpose.