[#method_override]
## method::override

### Synopsis

```c++
namespace boost::openmethod {

template<typename Signature, typename ReturnType, class Policy>
template<auto... Functions>
struct method<Signature, ReturnType, Policy>::override {
    override();
    ~override();
};

}
```

Usage:
```c++
method<Signature, ReturnType, Policy>::override<Functions...> some_unique_name;
  // at file scope
```

### Description

`override`, instantiated as a static object, add one or more overriders to an
open-method.

_Functions_ must fulfill the following requirements:

* Have the same number of formal parameters as the method.

* Each parameter in the same position as a `virtual_ptr<T>` in the method's
parameter list must be a `virtual_ptr<U>`, where _U_ is covariant with _T_. The
_Policy_ of the `virtual_ptr`{empty}s must be the same as the method's _Policy_.

* Each formal parameter in the same position as a `virtual_` parameter must have
a type that is covariant with the type of the method's parameter.

* All other formal parameters must have the same type as the method's
  corresponding parameters.

* The return type of the overrider must be the same as the method's return type
  or, if it is a polymorphic type, covariant with the method's return type.

### Members

#### constructor

```c++
override<Functions>::override();
```

Add _Functions_ to the overriders of `method`.

#### Destructor

```c++
override<Functions>::~method();
```

Remove _Functions_ from the overriders of `method`.