Confusing parsing error message when trying to use True as keyword argument

[cfbolz]

BPO	45716
Nosy	@cfbolz, @aroberge, @lysnikolaou, @pablogsal
PRs	bpo-45716: Improve the error message when using True/False/None as keywords in a call #29413 [3.10] bpo-45716: Improve the error message when using True/False/None as keywords in a call (GH-29413) #29428

^{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 2021-11-05.13:57:15.486>
created_at = <Date 2021-11-04.17:45:48.986>
labels = ['interpreter-core']
title = 'Confusing parsing error message when trying to use True as keyword argument'
updated_at = <Date 2021-11-16.22:31:49.761>
user = 'https://github.com/cfbolz'

bugs.python.org fields:

activity = <Date 2021-11-16.22:31:49.761>
actor = 'pablogsal'
assignee = 'none'
closed = True
closed_date = <Date 2021-11-05.13:57:15.486>
closer = 'pablogsal'
components = ['Parser']
creation = <Date 2021-11-04.17:45:48.986>
creator = 'Carl.Friedrich.Bolz'
dependencies = []
files = []
hgrepos = []
issue_num = 45716
keywords = ['patch']
message_count = 3.0
messages = ['405741', '405798', '406439']
nosy_count = 4.0
nosy_names = ['Carl.Friedrich.Bolz', 'aroberge', 'lys.nikolaou', 'pablogsal']
pr_nums = ['29413', '29428']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue45716'
versions = []

[cfbolz]

A bit of a nitpick, but the following SyntaxError message is a bit confusing:

>>> f(True=1)
  File "<stdin>", line 1
    f(True=1)
      ^^^^^
SyntaxError: expression cannot contain assignment, perhaps you meant "=="?

The problem with that line is not that it contains an assignment, it's almost a valid keyword argument after all. The problem is that the name of the keyword is True, which is no longer a name you can assign to. It would be better to produce the same error as with __debug__:

>>> f(__debug__=1)
  File "<stdin>", line 1
SyntaxError: cannot assign to __debug__

The latter error message is however produced by the compiler, not the parser I think?

[pablogsal]

New changeset e2d6563 by Pablo Galindo Salgado in branch 'main':
bpo-45716: Improve the error message when using True/False/None as keywords in a call (GH-29413)
e2d6563

[pablogsal]

New changeset 5618c81 by Pablo Galindo Salgado in branch '3.10':
[3.10] bpo-45716: Improve the error message when using True/False/None as keywords in a call (GH-29413). (GH-29428)
5618c81