“在非静态数据成员之前需要构造函数”-我是否使用“ boost :: variant”达到c ++核心问题1360？

有了这个代码

#include <boost/variant.hpp>
#include <string>

struct Outer
{
    struct StateA
    {
        std::size_t index = std::string::npos;
    };

    struct StateB {};

    using State = boost::variant<StateA, StateB>;

    struct Inner
    {
        State state = StateB{};
    };
};

int main() {
    Outer o;
    (void)o;
}

我收到以下编译错误

/usr/include/boost/variant/variant.hpp:1301:17:   required from ‘class boost::variant<Outer::StateA, Outer::StateB>’
inner_class.cpp:18:30:   required from here
/usr/include/boost/type_traits/has_nothrow_constructor.hpp:27:84: error: constructor required before non-static data member for ‘Outer::StateA::index’ has been parsed
 template <class T> struct has_nothrow_constructor : public integral_constant<bool, BOOST_HAS_NOTHROW_CONSTRUCTOR(T)>{};

关于这个问题，看来我正在解决这个核心问题，但是我想检查一下我的理解。

具体来说，我在打吗

当前文本中未指定的订单依存关系

什么时候初始化了我typedef的？还是有关inner的其他问题导致此编译错误？variantInnerstruct