Rename types.Union to types.UnionType

[serhiy-storchaka]

BPO	44732
Nosy	@gvanrossum, @ambv, @serhiy-storchaka, @JelleZijlstra, @pablogsal, @miss-islington, @AliyevH, @Fidget-Spinner
PRs	bpo-44732: Rename types.Union to types.UnionType #27342 [3.10] bpo-44732: Rename types.Union to types.UnionType (GH-27342) #27365

^{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 2021-07-26.19:03:15.666>
created_at = <Date 2021-07-24.09:24:20.429>
labels = ['interpreter-core', '3.10', '3.11']
title = 'Rename types.Union to types.UnionType'
updated_at = <Date 2021-07-26.19:03:15.666>
user = 'https://github.com/serhiy-storchaka'

bugs.python.org fields:

activity = <Date 2021-07-26.19:03:15.666>
actor = 'pablogsal'
assignee = 'none'
closed = True
closed_date = <Date 2021-07-26.19:03:15.666>
closer = 'pablogsal'
components = ['Interpreter Core']
creation = <Date 2021-07-24.09:24:20.429>
creator = 'serhiy.storchaka'
dependencies = []
files = []
hgrepos = []
issue_num = 44732
keywords = ['patch']
message_count = 8.0
messages = ['398128', '398130', '398177', '398185', '398190', '398210', '398238', '398247']
nosy_count = 8.0
nosy_names = ['gvanrossum', 'lukasz.langa', 'serhiy.storchaka', 'JelleZijlstra', 'pablogsal', 'miss-islington', 'AliyevH', 'kj']
pr_nums = ['27342', '27365']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue44732'
versions = ['Python 3.10', 'Python 3.11']

[serhiy-storchaka]

There are differences between typing.Union and types.Union:

• typing.Union is indexable, types.Union is not.
• types.Union is a class, typing.Union is not.

types.Union corresponds to typing._UnionGenericAlias, not typing.Union. It is confusing that typing.Union and types.Union have the same name. Note also that most classes in the types module have the "Type" suffix: FunctionType, MethodType, ModuleType, etc. I think that it would be better to rename types.Union to types.UnionType.

[AliyevH]

If nobody works on it i would like to fix it

[AliyevH]

should have a deprecation period and if so, how long?

[pablogsal]

This is a feature added to 3.10 so if we change it before the release there is no deprecation period needed. On the other hand if we don't get it to 3.10 is going to be much difficult to rename.

[gvanrossum]

Agreed. I think we should do it, Serhiy’s reasoning makes sense.

We should just update the PEP and add a note that this was changed during the beta period.

[JelleZijlstra]

I agree that UnionType is marginally better so we should rename it. It doesn't seem worth doing if this doesn't make it in in time for 3.10, though. With the advent of PEP-604 typing.Union will hopefully become irrelevant.

[ambv]

New changeset 2b8ad9e by Hasan in branch 'main':
bpo-44732: Rename types.Union to types.UnionType (bpo-27342)
2b8ad9e

[miss-islington]

New changeset 8a37e8c by Miss Islington (bot) in branch '3.10':
bpo-44732: Rename types.Union to types.UnionType (GH-27342)
8a37e8c