Also using getter_cpp_function for def_property_readonly.

Author: rwgk

include/pybind11/pybind11.h

@@ -1614,8 +1614,11 @@ class class_ : public detail::generic_type {
     template <typename C, typename D, typename... Extra>
     class_ &def_readonly(const char *name, const D C::*pm, const Extra& ...extra) {
         static_assert(std::is_same<C, type>::value || std::is_base_of<C, type>::value, "def_readonly() requires a class member (or base class member)");
-        cpp_function fget([pm](const type &c) -> const D &{ return c.*pm; }, is_method(*this));
-        def_property_readonly(name, fget, return_value_policy::reference_internal, extra...);
+        def_property_readonly(
+            name,
+            getter_cpp_function<type, D>::make(pm, is_method(*this)),
+            return_value_policy::reference_internal,
+            extra...);
         return *this;
     }