View source for cpp/error/rethrow if nested

===Possible implementation===
{{eq fun|1=
namespace details
{
    template<class E>
    struct can_dynamic_cast
        : std::integral_constant<bool,
              std::is_polymorphic<E>::value &&
              (!std::is_base_of<std::nested_exception, E>::value {{!!}} 
                std::is_convertible<E*, std::nested_exception*>::value)
          > {};

    template<class T>
    void rethrow_if_nested_impl(const T& e, std::true_type)
    {
        if (auto nep = dynamic_cast<const std::nested_exception*>(std::addressof(e)))
            nep->rethrow_nested();
    }

    template<class T>
    void rethrow_if_nested_impl(const T&, std::false_type) {}
}

template<class T>
void rethrow_if_nested(const T& t)
{
    details::rethrow_if_nested_impl(t, details::can_dynamic_cast<T>());
}
}}