bpo-43770: _PyTypes_Init() inits _PyAnextAwaitable_Type (GH-25266)

* Rename PyAnextAwaitable_Type to _PyAnextAwaitable_Type.
* Expose the type in the internal C API.

Author: vstinner

Include/iterobject.h

@@ -7,6 +7,9 @@ extern "C" {
 
 PyAPI_DATA(PyTypeObject) PySeqIter_Type;
 PyAPI_DATA(PyTypeObject) PyCallIter_Type;
+#ifdef Py_BUILD_CORE
+extern PyTypeObject _PyAnextAwaitable_Type;
+#endif
 
 #define PySeqIter_Check(op) Py_IS_TYPE(op, &PySeqIter_Type)
 

Objects/iterobject.c

@@ -333,7 +333,7 @@ static PyAsyncMethods anextawaitable_as_async = {
     0,                                          /* am_send  */
 };
 
-PyTypeObject PyAnextAwaitable_Type = {
+PyTypeObject _PyAnextAwaitable_Type = {
     PyVarObject_HEAD_INIT(&PyType_Type, 0)
     "anext_awaitable",                          /* tp_name */
     sizeof(anextawaitableobject),               /* tp_basicsize */
@@ -369,7 +369,7 @@ PyObject *
 PyAnextAwaitable_New(PyObject *awaitable, PyObject *default_value)
 {
     anextawaitableobject *anext = PyObject_GC_New(
-            anextawaitableobject, &PyAnextAwaitable_Type);
+            anextawaitableobject, &_PyAnextAwaitable_Type);
     if (anext == NULL) {
         return NULL;
     }

Objects/object.c

@@ -1833,6 +1833,7 @@ _PyTypes_Init(void)
     INIT_TYPE(PyUnicode_Type);
     INIT_TYPE(PyWrapperDescr_Type);
     INIT_TYPE(Py_GenericAliasType);
+    INIT_TYPE(_PyAnextAwaitable_Type);
     INIT_TYPE(_PyAsyncGenASend_Type);
     INIT_TYPE(_PyAsyncGenAThrow_Type);
     INIT_TYPE(_PyAsyncGenWrappedValue_Type);