inconsistent bahaviour of functools.partial python and C

[dg-pb]

Bug report

Bug description:

    def __new__(cls, func, /, *args, **keywords):
        ...
        if hasattr(func, "func"):

static PyObject *
partial_new(PyTypeObject *type, PyObject *args, PyObject *kw)
{
    int res = PyObject_TypeCheck(func, state->partial_type);
    ...
    if (res == 1) {

I believe python implementation should do:

if isinstance(func, cls):

Or were there any good reasons to check attribute instead?

CPython versions tested on:

3.11, 3.12

Operating systems tested on:

macOS

[sobolevn]

Thanks for the report!

But, I think that this is duplicate of #100242