std::error_code::operator bool
From cppreference.com
                    
                                        
                    < cpp | error | error code
                    
                                                            
                    | explicit operator bool() const noexcept; | (since C++11) | |
Checks if the error value is valid, i.e. non-zero.
Parameters
(none)
Return value
false if value() == 0, true otherwise.