Add a direct converter for numpy scalars

include/pybind11/numpy.h

@@ -63,6 +63,14 @@ struct PyArray_Proxy {
     int flags;
 };
 
+struct PyVoidScalarObject_Proxy {
+    PyObject_VAR_HEAD
+    char *obval;
+    PyArrayDescr_Proxy *descr;
+    int flags;
+    PyObject *base;
+};
+
 struct npy_api {
     enum constants {
         NPY_C_CONTIGUOUS_ = 0x0001,
@@ -702,11 +710,29 @@ struct npy_format_descriptor<T, enable_if_t<is_pod_struct<T>::value>> {
         auto arr =  array(buffer_info(nullptr, sizeof(T), format(), 1));
         if (!api.PyArray_EquivTypes_(dtype_ptr, arr.dtype().ptr()))
             pybind11_fail("NumPy: invalid buffer descriptor!");
+
+        register_direct_converter();
     }
 
 private:
     static std::string format_str;
     static PyObject* dtype_ptr;
+
+    static void register_direct_converter() {
+        auto converter = [=](PyObject *obj, void*& value) {
+            auto& api = npy_api::get();
+            if (!PyObject_TypeCheck(obj, api.PyVoidArrType_Type_))
+                return false;
+            if (auto descr = object(api.PyArray_DescrFromScalar_(obj), false)) {
+                if (api.PyArray_EquivTypes_(dtype_ptr, descr.ptr())) {
+                    value = ((PyVoidScalarObject_Proxy *) obj)->obval;
+                    return true;
+                }
+            }
+            return false;
+        };
+        get_internals().direct_conversions[std::type_index(typeid(T))].push_back(converter);
+    }
 };
 
 template <typename T>