[BUG]: Warning on MSVC when defining functions that accept raw function pointers

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Problem description

I have a C function that I'm binding to Python that excepts a raw function pointer. On MSVC I get warning 4180 when compiling.
I'm pretty sure that raw function pointers aren't supported, but it should probably give either an error or do nothing, not a warning.
Compile the example code with something like:
cl /nologo -IC:\python\include -IC:\py\git\pybind11\include /EHsc /Febug.pyd /LD /MDd C:\python\libs\python39.lib

Reproducible example code

#include "pybind11/pybind11.h"
using namespace pybind11;
typedef int (* callback)(int a, int b);


int add_with_callback(callback callback, int a, int b) {
	return callback(a, b);
}
PYBIND11_MODULE(bug, m) {
	m.def("add_with_callback", &add_with_callback);
}

Start with the reproducible C++ example and the provided MSVC command, then trace the binding path reached by m.def for a raw function pointer. Determine whether the supported outcome is warning-free handling or an explicit error; done means rebuilding the example produces that deliberate outcome without warning 4180.