Expose Py_tp_vectorcall in the limited API #41
Description
tp_vectorcall is somewhat tricky to understand, but can bring significant speedups to wrapper code.
In python/cpython#100554, pybind11 and PyO3 maintainers ask to expose it for use with PyType_FromSpec/PyType_GetSlot and in limited API, and Wenzel sent a PR recently.
tp_vectorcall needs to match the behavior of a metaclass call, so exposing tp_vectorcall limits future changes to PyType_Type->tp_call. But, I think that's already something we can't really change.
Does a Py_tp_vectorcall slot sound reasonable?