Use `dynamic_cast` to a reference type when failure to find the required class is considered an error

Reason

Casting to a reference expresses that you intend to end up with a valid object, so the cast must succeed. dynamic_cast will then throw if it does not succeed.

Example

std::string f(Base& b)
{
    return dynamic_cast<Derived&>(b).to_string();
}

Enforcement

???