remove type_slot_callbacks feature, minor fixes

docs/api_core.rst

@@ -1876,24 +1876,6 @@ declarations in generated :ref:`stubs <stubs>`,
    zero-initialized ``PyType_Slot`` element. See :ref:`Customizing type creation
    <typeslots>` for more information about this feature.
 
-.. cpp:struct:: type_slots_callback
-
-   .. cpp:function:: type_slots_callback(void (* callback)(detail::type_init_data * , PyType_Slot * &slots, size_t max_slots) noexcept)
-
-   This is an alternative to `type_slots` that provides a callback
-   which will be invoked during type creation to populate the type's
-   list of slots. It is used by `enum_`. It can be used in addition to
-   the `type_slots` annotation; if both are provided,
-   `type_slots_callback` runs first (so `type_slots` can override its choices).
-
-   The callback should execute ``*slots++ = {Py_tp_foo, (void *) handle_foo};``
-   at most *max_slots* times.
-
-   Information about the type under construction is available via the first
-   parameter received by the callback, but be aware that this is an internal
-   type which is not subject to nanobind's usual semantic versioning guarantees.
-   See ``include/nanobind/nb_class.h`` for more details.
-
 .. cpp:struct:: template <typename T> intrusive_ptr
 
    nanobind provides a custom interface for intrusive reference-counted C++

include/nanobind/nb_class.h

@@ -85,8 +85,7 @@ enum class type_init_flags : uint32_t {
     /// Is the 'base_py' field of the type_init_data structure set?
     has_base_py              = (1 << 22),
 
-    /// This type provides extra PyType_Slot fields via the 'type_slots'
-    /// and/or 'type_slots_callback' members of type_init_data
+    /// This type provides extra PyType_Slot fields
     has_type_slots           = (1 << 23),
 
     all_init_flags           = (0x1f << 19)
@@ -135,7 +134,6 @@ struct type_init_data : type_data {
     PyTypeObject *base_py;
     const char *doc;
     const PyType_Slot *type_slots;
-    void (*type_slots_callback)(const type_init_data *d, PyType_Slot *&slots, size_t max_slots);
     size_t supplement;
 };
 
@@ -150,21 +148,10 @@ NB_INLINE void type_extra_apply(type_init_data &t, const char *doc) {
 }
 
 NB_INLINE void type_extra_apply(type_init_data &t, type_slots c) {
-    if ((t.flags & (uint32_t) type_init_flags::has_type_slots) == 0) {
-        t.flags |= (uint32_t) type_init_flags::has_type_slots;
-        t.type_slots_callback = nullptr;
-    }
+    t.flags |= (uint32_t) type_init_flags::has_type_slots;
     t.type_slots = c.value;
 }
 
-NB_INLINE void type_extra_apply(type_init_data &t, type_slots_callback c) {
-    if ((t.flags & (uint32_t) type_init_flags::has_type_slots) == 0) {
-        t.flags |= (uint32_t) type_init_flags::has_type_slots;
-        t.type_slots = nullptr;
-    }
-    t.type_slots_callback = c.callback;
-}
-
 template <typename T>
 NB_INLINE void type_extra_apply(type_init_data &t, intrusive_ptr<T> ip) {
     t.flags |= (uint32_t) type_flags::intrusive_ptr;

src/nb_type.cpp

@@ -359,7 +359,6 @@ void nb_type_unregister(type_data *t) noexcept {
         }
     }
 
-
     check(!fail,
           "nanobind::detail::nb_type_unregister(\"%s\"): could not "
           "find type!", t->name);
@@ -980,22 +979,12 @@ PyObject *nb_type_new(const type_init_data *t) noexcept {
 
     if (has_type_slots) {
         size_t num_avail = nb_extra_slots;
-        if (t->type_slots_callback) {
-            PyType_Slot* first_new = s;
-            t->type_slots_callback(t, s, num_avail);
-            check(first_new + num_avail >= s,
-                  "nanobind::detail::nb_type_new(\"%s\"): type_slots_callback "
-                  "overflowed the slots array!", t_name);
-            num_avail -= (s - first_new);
-        }
-        if (t->type_slots) {
-            size_t i = 0;
-            while (t->type_slots[i].slot) {
-                check(i != num_avail,
-                      "nanobind::detail::nb_type_new(\"%s\"): ran out of "
-                      "type slots!", t_name);
-                *s++ = t->type_slots[i++];
-            }
+        size_t i = 0;
+        while (t->type_slots[i].slot) {
+            check(i != num_avail,
+                  "nanobind::detail::nb_type_new(\"%s\"): ran out of "
+                  "type slots!", t_name);
+            *s++ = t->type_slots[i++];
         }
     }