bpo-43977: Use tp_flags for collection matching (GH-25723)

* Add Py_TPFLAGS_SEQUENCE and Py_TPFLAGS_MAPPING, add to all relevant standard builtin classes.

* Set relevant flags on collections.abc.Sequence and Mapping.

* Use flags in MATCH_SEQUENCE and MATCH_MAPPING opcodes.

* Inherit Py_TPFLAGS_SEQUENCE and Py_TPFLAGS_MAPPING.

* Add NEWS

* Remove interpreter-state map_abc and seq_abc fields.

2 files changed, 8 insertions, 66 deletions

diff --git a/Python/ceval.c b/Python/ceval.c
index 326930b..866c57a 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -3889,76 +3889,20 @@ main_loop:
         }
 
         case TARGET(MATCH_MAPPING): {
-            // PUSH(isinstance(TOS, _collections_abc.Mapping))
             PyObject *subject = TOP();
-            // Fast path for dicts:
-            if (PyDict_Check(subject)) {
-                Py_INCREF(Py_True);
-                PUSH(Py_True);
-                DISPATCH();
-            }
-            // Lazily import _collections_abc.Mapping, and keep it handy on the
-            // PyInterpreterState struct (it gets cleaned up at exit):
-            PyInterpreterState *interp = PyInterpreterState_Get();
-            if (interp->map_abc == NULL) {
-                PyObject *abc = PyImport_ImportModule("_collections_abc");
-                if (abc == NULL) {
-                    goto error;
-                }
-                interp->map_abc = PyObject_GetAttrString(abc, "Mapping");
-                if (interp->map_abc == NULL) {
-                    goto error;
-                }
-            }
-            int match = PyObject_IsInstance(subject, interp->map_abc);
-            if (match < 0) {
-                goto error;
-            }
-            PUSH(PyBool_FromLong(match));
+            int match = Py_TYPE(subject)->tp_flags & Py_TPFLAGS_MAPPING;
+            PyObject *res = match ? Py_True : Py_False;
+            Py_INCREF(res);
+            PUSH(res);
             DISPATCH();
         }
 
         case TARGET(MATCH_SEQUENCE): {
-            // PUSH(not isinstance(TOS, (bytearray, bytes, str))
-            //      and isinstance(TOS, _collections_abc.Sequence))
             PyObject *subject = TOP();
-            // Fast path for lists and tuples:
-            if (PyType_FastSubclass(Py_TYPE(subject),
-                                    Py_TPFLAGS_LIST_SUBCLASS |
-                                    Py_TPFLAGS_TUPLE_SUBCLASS))
-            {
-                Py_INCREF(Py_True);
-                PUSH(Py_True);
-                DISPATCH();
-            }
-            // Bail on some possible Sequences that we intentionally exclude:
-            if (PyType_FastSubclass(Py_TYPE(subject),
-                                    Py_TPFLAGS_BYTES_SUBCLASS |
-                                    Py_TPFLAGS_UNICODE_SUBCLASS) ||
-                PyByteArray_Check(subject))
-            {
-                Py_INCREF(Py_False);
-                PUSH(Py_False);
-                DISPATCH();
-            }
-            // Lazily import _collections_abc.Sequence, and keep it handy on the
-            // PyInterpreterState struct (it gets cleaned up at exit):
-            PyInterpreterState *interp = PyInterpreterState_Get();
-            if (interp->seq_abc == NULL) {
-                PyObject *abc = PyImport_ImportModule("_collections_abc");
-                if (abc == NULL) {
-                    goto error;
-                }
-                interp->seq_abc = PyObject_GetAttrString(abc, "Sequence");
-                if (interp->seq_abc == NULL) {
-                    goto error;
-                }
-            }
-            int match = PyObject_IsInstance(subject, interp->seq_abc);
-            if (match < 0) {
-                goto error;
-            }
-            PUSH(PyBool_FromLong(match));
+            int match = Py_TYPE(subject)->tp_flags & Py_TPFLAGS_SEQUENCE;
+            PyObject *res = match ? Py_True : Py_False;
+            Py_INCREF(res);
+            PUSH(res);
             DISPATCH();
         }
 
diff --git a/Python/pystate.c b/Python/pystate.c
index 81bcf68..aeebd6f 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -308,8 +308,6 @@ interpreter_clear(PyInterpreterState *interp, PyThreadState *tstate)
     Py_CLEAR(interp->importlib);
     Py_CLEAR(interp->import_func);
     Py_CLEAR(interp->dict);
-    Py_CLEAR(interp->map_abc);
-    Py_CLEAR(interp->seq_abc);
 #ifdef HAVE_FORK
     Py_CLEAR(interp->before_forkers);
     Py_CLEAR(interp->after_forkers_parent);