std::nested_exception::operator=
From cppreference.com
                    
                                        
                    < cpp | error | nested exception
                    
                                                            
                    | nested_exception& operator=( const nested_exception& other ) = default; | (since C++11) | |
Replaces the stored exception with the one held in other.
Parameters
| other | - | nested exception to replace the contents with | 
Return value
*this
Exceptions
noexcept specification:  
noexcept