Failed to cast std::optional to None in C++[Done]

[devsave]

Hello, this is a very easy scenario when I wrote below code, an assert raised:

terminate called after throwing an instance of 'pybind11::cast_error'
what(): Unable to convert call argument '0' of type 'std::optional' to Python object

I am using C++17, so std::optional is supported.

#include <pybind11/pybind11.h>
#include <pybind11/embed.h>
#include <optional>

namespace py=pybind11;

int main() {
    py::scoped_interpreter guard{};
    std::optional<int> a;
    py::print(a);
}

It looks I need to copy the optional caster from stl.h to cast.h and it works, is there a better solution?

Similar issues happened when I put a customer type whose bind have been defined.

struct Range
{
    BrRange(int a, int b):start(a), end(b){}
    int start = 0;
    int end = 0;
};

py::class_<Range>(m, "range")
    .def(py::init<int, int>())
    .def_readwrite("start", &Range::start)
    .def_readwrite("end", &Range::end);

The range instance can be casted to a python object while the std::vector<Range> failed to cast.

Hope any one can help, thanks so much!

[devsave]

Resolved.