dataclasses InitVar does not maintain any type info

[reinhrst]

BPO	33569
Nosy	@ericvsmith, @ilevkivskyi, @reinhrst, @hackaugusto
PRs	bpo-33569 Preserve type information with InitVar #8927

^{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 = 'https://github.com/ericvsmith'
closed_at = <Date 2019-06-03.02:15:21.610>
created_at = <Date 2018-05-18.12:39:55.384>
labels = ['type-bug', '3.7']
title = 'dataclasses InitVar does not maintain any type info'
updated_at = <Date 2019-06-03.02:15:21.610>
user = 'https://github.com/reinhrst'

bugs.python.org fields:

activity = <Date 2019-06-03.02:15:21.610>
actor = 'eric.smith'
assignee = 'eric.smith'
closed = True
closed_date = <Date 2019-06-03.02:15:21.610>
closer = 'eric.smith'
components = []
creation = <Date 2018-05-18.12:39:55.384>
creator = 'reinhrst'
dependencies = []
files = []
hgrepos = []
issue_num = 33569
keywords = ['patch']
message_count = 7.0
messages = ['317026', '317343', '323804', '324001', '324025', '344367', '344368']
nosy_count = 4.0
nosy_names = ['eric.smith', 'levkivskyi', 'reinhrst', 'hack.augusto']
pr_nums = ['8927']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue33569'
versions = ['Python 3.7']

[reinhrst]

Right now dataclasses.InitVar[something] is dataclasses.InitVar. This means that any type-information is removed, and it will (for instance) be impossible to do (runtime) type info checks on the generated __init__, or find out anything about the type of the variable.

[ericvsmith]

This seems like a reasonable request.

[hackaugusto]

I have made some changes to expose the InitVar type, they are available here:

https://github.com/hackaugusto/dataclasses/tree/initvar_type

Are these changes sufficient?

[ericvsmith]

Can you create a pull request? It's easier to review that way.

[ericvsmith]

test message, please ignore

[ericvsmith]

New changeset 01ee12b by Eric V. Smith (Augusto Hack) in branch 'master':
bpo-33569 Preserve type information with dataclasses.InitVar (GH-8927)
01ee12b

[ericvsmith]

Thanks for the PR!