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used-before-assignment false positive when walrus / assignment expression assigned and used in same expression #3953

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OJFord opened this issue Nov 23, 2020 · 2 comments · Fixed by #4064
Closed

used-before-assignment false positive when walrus / assignment expression assigned and used in same expression #3953

OJFord opened this issue Nov 23, 2020 · 2 comments · Fixed by #4064
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Assignment expression Related to the walrus operator / assignment expression Bug 🪲 False Positive 🦟 A message is emitted but nothing is wrong with the code

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@OJFord
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OJFord commented Nov 23, 2020

Similar to #3249

Steps to reproduce

  1. assert (n := len(stuff)) == 123, f"Expected length 123, but got {n}"
  2. pylint

Current behavior

E0601: Using variable 'n' before assignment (used-before-assignment)

Expected behavior

Pass.

pylint --version output

v2.6.0
@OJFord
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OJFord commented Nov 24, 2020

Another example (not using assert):

dict({"options": (d := json.loads(data))}, data=d["data"])

@OJFord OJFord changed the title used-before-assignment false positive with assert walrus / assignment expression, using assigned var used in second arg used-before-assignment false positive with walrus / assignment expression assigned and used in fn arguments Nov 24, 2020
@OJFord
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OJFord commented Nov 26, 2020

Also in ternaries, e.g.:

foo = m.group("foo") if (m := FOO_PATT.match(bar)) else "bar"

@OJFord OJFord changed the title used-before-assignment false positive with walrus / assignment expression assigned and used in fn arguments used-before-assignment false positive when walrus / assignment expression assigned and used in same expression Nov 26, 2020
@DakshChan DakshChan mentioned this issue Nov 29, 2020
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@hippo91 hippo91 added Bug 🪲 False Positive 🦟 A message is emitted but nothing is wrong with the code Assignment expression Related to the walrus operator / assignment expression labels Dec 1, 2020
@cdce8p cdce8p mentioned this issue Feb 3, 2021
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Labels
Assignment expression Related to the walrus operator / assignment expression Bug 🪲 False Positive 🦟 A message is emitted but nothing is wrong with the code
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Fix multiple false positives with assignment expressions
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@OJFord @hippo91