No, it's the other way around. Concepts are pretty useless at the moment for error messages, but they're super easy and convenient when you need to disambiguat

No, it's the other way around. Concepts are pretty useless at the moment for error messages, but they're super easy and convenient when you need to disambiguate something like void do_it(auto& x) { // x is a vector void do_it(auto& x) { // x is nlohmann::json Just stick a 'requires' in there and it works.