ast.Slice is no longer a subclass of ast.slice

[asottile]

BPO	40430
Nosy	@serhiy-storchaka, @asottile, @isidentical, @iritkatriel

^{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 = <Date 2020-10-05.16:54:12.316>
created_at = <Date 2020-04-28.22:48:03.631>
labels = ['type-bug', 'library', '3.9']
title = 'ast.Slice is no longer a subclass of ast.slice'
updated_at = <Date 2020-10-05.16:54:12.316>
user = 'https://github.com/asottile'

bugs.python.org fields:

activity = <Date 2020-10-05.16:54:12.316>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2020-10-05.16:54:12.316>
closer = 'serhiy.storchaka'
components = ['Library (Lib)']
creation = <Date 2020-04-28.22:48:03.631>
creator = 'Anthony Sottile'
dependencies = []
files = []
hgrepos = []
issue_num = 40430
keywords = []
message_count = 4.0
messages = ['367571', '367584', '377185', '378066']
nosy_count = 4.0
nosy_names = ['serhiy.storchaka', 'Anthony Sottile', 'BTaskaya', 'iritkatriel']
pr_nums = []
priority = 'normal'
resolution = 'wont fix'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue40430'
versions = ['Python 3.9']

[asottile]

unclear if this is intentional or not, I noticed this while seeing that ast.Subscript.slice is no longer Index / Slice / ExtSlice

# python3.8

>>> isinstance(ast.Slice(), ast.slice)
True

# python3.9a6

>>> isinstance(ast.Slice(), ast.slice)
False

[isidentical]

This has been discussee and rejected (for certain reasonsons): #19056 (comment)

[iritkatriel]

Looks like the answer is: it is a deliberate change, not a bug. Should this issue be closed?

[serhiy-storchaka]

Even if make ast.Slice a (virtual) subclass of ast.slice it will not help much, because we cannot do it for ast.Index and ast.ExtSlice. ast.ExtSlice is not replaced with ast.Tuple, and any node type can now be used instead of ast.Index. The code that does isinstance() or issublass() check for ast.slice or one of its subcasses is now broken.