bpo-34100: Partially revert merge_consts_recursive() (GH-10743)

Partically revert commit c2e1607 to fix a reference leak.

Author: vstinner

Lib/test/test_compile.py

@@ -615,16 +615,6 @@ def check_same_constant(const):
  self.check_constant(f1, Ellipsis)
  self.assertEqual(repr(f1()), repr(Ellipsis))
 
- # Merge constants in tuple or frozenset
- # NOTE: frozenset can't reuse previous const, but frozenset
- # item can be reused later.
- f3 = lambda x: x in {("not a name",)}
- f1, f2 = lambda: "not a name", lambda: ("not a name",)
- self.assertIs(next(iter(f3.__code__.co_consts[1])),
- f2.__code__.co_consts[1])
- self.assertIs(f1.__code__.co_consts[1],
- f2.__code__.co_consts[1][0])
-
  # {0} is converted to a constant frozenset({0}) by the peephole
  # optimizer
  f1, f2 = lambda x: x in {0}, lambda x: x in {0}

Python/compile.c

@@ -1240,56 +1240,6 @@ merge_consts_recursive(struct compiler *c, PyObject *o)
  Py_DECREF(u);
  }
  }
- else if (PyFrozenSet_CheckExact(o)) {
- // We register items in the frozenset, but don't rewrite
- // the frozenset when the item is already registered
- // because frozenset is rare and difficult.
-
- // *key* is tuple. And it's first item is frozenset of
- // constant keys.
- // See _PyCode_ConstantKey() for detail.
- assert(PyTuple_CheckExact(key));
- assert(PyTuple_GET_SIZE(key) == 2);
-
- Py_ssize_t len = PySet_GET_SIZE(o);
- if (len == 0) {
- return key;
- }
- PyObject *tuple = PyTuple_New(len);
- if (tuple == NULL) {
- Py_DECREF(key);
- return NULL;
- }
- Py_ssize_t i = 0, pos = 0;
- PyObject *item;
- Py_hash_t hash;
- while (_PySet_NextEntry(o, &pos, &item, &hash)) {
- PyObject *k = merge_consts_recursive(c, item);
- if (k == NULL) {
- Py_DECREF(tuple);
- Py_DECREF(key);
- return NULL;
- }
- PyObject *u;
- if (PyTuple_CheckExact(k)) {
- u = PyTuple_GET_ITEM(k, 1);
- }
- else {
- u = k;
- }
- Py_INCREF(u);
- PyTuple_SET_ITEM(tuple, i, u);
- i++;
- }
-
- PyObject *new = PyFrozenSet_New(tuple);
- Py_DECREF(tuple);
- if (new == NULL) {
- Py_DECREF(key);
- return NULL;
- }
- PyTuple_SET_ITEM(key, 1, new);
- }
 
  return key;
 }