What's the correct `enable_if` constraint on perfect forwarding setter?

Question

Herb Sutter\'s Back to the Basics! Essentials of Modern C++ presentation at CppCon discussed different options for passing parameters and compared their performance

Answer 1

I think what you have is probably right, but in the interest of not writing an "answer" that is simply "I agree", I will propose this instead that will check assignment based on the correct types - whether it's an lval, rval, const, whatever:

template 
auto set_name(String&& name) 
-> decltype(name_ = std::forward(name), void()) {
    name_ = std::forward(name);
}