bpo-39474: Fix AST pos for expressions like (a)(b), (a)[b] and (a).b.

[serhiy-storchaka]

https://bugs.python.org/issue39474

[codecov]

Codecov Report

Merging #18477 into master will increase coverage by 0.00%.
The diff coverage is n/a.

@@ Coverage Diff @@ ## master #18477 +/- ## ========================================= Coverage 82.11% 82.12% ========================================= Files 1956 1955 -1 Lines 589067 583729 -5338 Branches 44436 44437 +1 ========================================= - Hits 483723 479376 -4347  + Misses 95690 94708 -982  + Partials 9654 9645 -9 

Impacted Files	Coverage Δ
Lib/distutils/tests/test_bdist_rpm.py	30.00% <0.00%> (-65.00%)	⬇️
Lib/distutils/command/bdist_rpm.py	7.63% <0.00%> (-56.88%)	⬇️
Lib/test/test_urllib2net.py	76.92% <0.00%> (-13.85%)	⬇️
Lib/test/test_smtpnet.py	78.57% <0.00%> (-7.15%)	⬇️
Lib/ftplib.py	63.85% <0.00%> (-6.06%)	⬇️
Lib/test/test_ftplib.py	87.11% <0.00%> (-4.72%)	⬇️
Tools/scripts/db2pickle.py	17.82% <0.00%> (-3.97%)	⬇️
Tools/scripts/pickle2db.py	16.98% <0.00%> (-3.78%)	⬇️
Lib/test/test_socket.py	71.94% <0.00%> (-3.77%)	⬇️
Lib/test/test_asyncio/test_base_events.py	91.84% <0.00%> (-3.30%)	⬇️
... and 327 more

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[lysnikolaou]

LGTM!

[gvanrossum]

From a quick glance LG.

Would it make sense to add a test for e.g. ((a)).b?

[serhiy-storchaka]

We can add complex examples like ((((a+b).c)[d])(e))().f, but it would not cover anything that was not already covered by the minimal example (a).b.

[gvanrossum]

I don't need complex example, but I'd like a single example showing ((a)).b, since IIRC there's some special code involved in removing redundant parentheses, and I feel that that special case was involved in the bug in the first place.

[gvanrossum]

Honestly I take it back, you can land.

[miss-islington]

Thanks @serhiy-storchaka for the PR 🌮🎉.. I'm working now to backport this PR to: 3.8.
🐍🍒⛏🤖

[bedevere-bot]

GH-18491 is a backport of this pull request to the 3.8 branch.