Make use of new `py::buffer_info::item_type_is_equivalent_to<T>()`

The new member function was added with https://github.com/pybind/pybind11/pull/4674

PiperOrigin-RevId: 534952040

pybind11_abseil/absl_casters.h

@@ -386,8 +386,6 @@ template <>
 struct type_caster<absl::CivilYear>
     : public absl_civil_date_caster<absl::CivilYear> {};
 
-// Using internal namespace to avoid name collisons in case this code is
-// accepted upsteam (pybind11).
 namespace internal {
 
 template <typename T>
@@ -397,33 +395,6 @@ static constexpr bool is_buffer_interface_compatible_type =
     std::is_same<T, std::complex<float>>::value ||
     std::is_same<T, std::complex<double>>::value;
 
-template <typename T, typename SFINAE = void>
-struct format_descriptor_char1 : format_descriptor<T> {};
-
-template <typename T>
-struct format_descriptor_char1<
-    T,
-    detail::enable_if_t<detail::is_same_ignoring_cvref<T, PyObject*>::value>> {
-  static constexpr const char c = 'O';
-  static constexpr const char value[2] = {c, '\0'};
-  static std::string format() { return std::string(1, c); }
-};
-
-template <typename T, typename SFINAE = void>
-struct format_descriptor_char2 {
-  static constexpr const char c = '\0';
-};
-
-template <typename T>
-struct format_descriptor_char2<std::complex<T>> : format_descriptor<T> {};
-
-template <typename T>
-inline bool buffer_view_matches_format_descriptor(const char* view_format) {
-  return view_format[0] == format_descriptor_char1<T>::c ||
-         (view_format[0] == 'Z' &&
-          view_format[1] == format_descriptor_char2<T>::c);
-}
-
 }  // namespace internal
 
 // Returns {true, a span referencing the data contained by src} without copying
@@ -438,7 +409,7 @@ std::tuple<bool, absl::Span<T>> LoadSpanFromBuffer(handle src) {
   if (PyObject_GetBuffer(src.ptr(), &view, flags) == 0) {
     auto cleanup = absl::MakeCleanup([&view] { PyBuffer_Release(&view); });
     if (view.ndim == 1 && view.strides[0] == sizeof(T) &&
-        internal::buffer_view_matches_format_descriptor<T>(view.format)) {
+        buffer_info(&view, /*ownview=*/false).item_type_is_equivalent_to<T>()) {
       return {true, absl::MakeSpan(static_cast<T*>(view.buf), view.shape[0])};
     }
   } else {