Bug report

Bug description:

When inserting a class member during some other class member's __set_name__ call, the __set_name__ method of the newly-inserted member doesn't get called as expected.

As an example, take this snippet:

class I_Am_Altering_The_Deal:
    def __set_name__(self, owner, name):
        print(f"__set_name__({self.__class__.__name__}, {owner.__name__}, {name!r}")
        owner.han_solo = Pray_I_Dont_Alter_It_Any_Further()
        
class Pray_I_Dont_Alter_It_Any_Further:
    def __set_name__(self, owner, name):
        print(f"__set_name__({self.__class__.__name__}, {owner.__name__}, {name!r}")

class Cloud_City:
    luke_skywalker = I_Am_Altering_The_Deal()

I would expect both __set_name__ functions to be called, resulting in the output:

__set_name__(I_Am_Altering_The_Deal, Cloud_City, 'luke_skywalker')
__set_name__(Pray_I_Dont_Alter_It_Any_Further, Cloud_City, 'han_solo')

But what is actually output, is:

__set_name__(I_Am_Altering_The_Deal, Cloud_City, 'luke_skywalker')

Discovered while testing a PEP-487 implementation for Micropython: micropython/micropython#15503.

Maybe be related to #72983.

CPython versions tested on:

3.8, 3.10, 3.12

Operating systems tested on:

Linux