Make sure that tp_as_xxx methods are never NULL in PyType_Ready()

PyType_Ready() now sets type tp_as_xxx members to a structure filled
of NULL if a member is NULL. It avoids checking if tp_as_xxx is NULL
in Objects/abstract.c functions.

Author: vstinner

Include/internal/pycore_abstract.h

@@ -12,8 +12,7 @@ extern "C" {
 static inline int
 _PyIndex_Check(PyObject *obj)
 {
-    PyNumberMethods *tp_as_number = Py_TYPE(obj)->tp_as_number;
-    return (tp_as_number != NULL && tp_as_number->nb_index != NULL);
+    return (Py_TYPE(obj)->tp_as_number->nb_index != NULL);
 }
 
 // Exported for external JIT support

Include/internal/pycore_slots_generated.h

@@ -35,11 +35,11 @@ get_sq_item(PyObject *s)
     // The parts of PySequence_GetItem that we only need to do once
     PyTypeObject *tp = Py_TYPE(s);
     PySequenceMethods *m = tp->tp_as_sequence;
-    if (m && m->sq_item) {
+    if (m->sq_item) {
         return m->sq_item;
     }
     const char *msg;
-    if (tp->tp_as_mapping && tp->tp_as_mapping->mp_subscript) {
+    if (tp->tp_as_mapping->mp_subscript) {
         msg = "%.200s is not a sequence";
     }
     else {