WeakKeyDictionary should support lookup by id instead of hash

[conchylicultor]

BPO	44140
Nosy	@MojoVampire, @youtux, @brandtbucher, @Conchylicultor, @akulakov

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-05-15.08:42:51.954>
labels = ['3.7', '3.8', '3.9', '3.10', '3.11', 'type-feature', 'library']
title = 'WeakKeyDictionary should support lookup by id instead of hash'
updated_at = <Date 2021-08-26.22:27:51.360>
user = 'https://github.com/conchylicultor'

bugs.python.org fields:

activity = <Date 2021-08-26.22:27:51.360>
actor = 'youtux'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2021-05-15.08:42:51.954>
creator = 'conchylicultor'
dependencies = []
files = []
hgrepos = []
issue_num = 44140
keywords = []
message_count = 4.0
messages = ['393707', '396362', '396451', '396452']
nosy_count = 5.0
nosy_names = ['josh.r', 'youtux', 'brandtbucher', 'conchylicultor', 'andrei.avk']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue44140'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8', 'Python 3.9', 'Python 3.10', 'Python 3.11']

[conchylicultor]

WeakKeyDictionary are great to "associate additional data with an object owned by other parts of an application", as quoted from the doc: https://docs.python.org/3/library/weakref.html#weakref.WeakKeyDictionary

However, this currently only works for hashable types. Non-hashables are not supported:

@dataclass
class A:
  pass

a = A()

d = weakref.WeakKeyDictionary()
d[a] = 3  # TypeError: unhashable type: 'A'

With regular dict, this could be easilly solved by using d[id(a)] = 3, but WeakKeyDictionary don't accept int of course. I cannot wrap the object either as the weakref would not be attached to the original object, but the wrapper.

It would be great to be able to force WeakKeyDictionary to perform lookup on id internally. Like d = WeakKeyDictionary(use_id_lookup=True)