gh-149534: Fix unification of defaultdict and frozendict with |

[sobolevn]

I have a lot of free time today 😆

[JelleZijlstra]

Can you also test what frozendict | defaultdict does?

[sobolevn]

@JelleZijlstra you were right, there's a big behavior difference here.

>>> from collections import OrderedDict
>>> dict() | OrderedDict()
OrderedDict()
>>> frozendict() | OrderedDict()
frozendict()

Since OrderedDict and defaultdict are direct subtypes of dict, _PyDict_Or is never called for the first case.

cpython/Objects/typeobject.c

Lines 10531 to 10539 in 354ef33

	#define SLOT1BINFULL(FUNCNAME, TESTFUNC, SLOTNAME, DUNDER, RDUNDER) \
	static PyObject * \
	FUNCNAME(PyObject *self, PyObject *other) \
	{ \
	PyObject* stack[2]; \
	PyThreadState *tstate = _PyThreadState_GET(); \
	int do_other = !Py_IS_TYPE(self, Py_TYPE(other)) && \
	Py_TYPE(other)->tp_as_number != NULL && \
	Py_TYPE(other)->tp_as_number->SLOTNAME == TESTFUNC; \

While it is called for frozendict.

I am not sure that this is a bug, though. It works as expected,, if you know all the little details. But, it might be unexpected for people who just want to swap dict to frozendict. The end result might be different.

@vstinner, what do you think?

[JelleZijlstra]

I don't have a strong opinion on what the right behavior is, but let's make sure that OrderedDict and defaultdict behave consistently at least.