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Fix false positive used-before-assignment in pattern matching with a guard #7793

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Fix false positive used-before-assignment in pattern matching with a guard #7793

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b38da73
Fix false positive `used-before-assignment` in pattern matching with …
Nov 18, 2022
c7e0122
Typo fix
Nov 18, 2022
b6bfabe
Added whatsnew
Nov 18, 2022
2e5baef
[pre-commit.ci] auto fixes from pre-commit.com hooks
pre-commit-ci[bot] Nov 18, 2022
5a0e6ee
Whatsnew format fix
Nov 18, 2022
727feaa
Py10 and up only
Nov 18, 2022
cd31a5a
Catch up with main
Nov 18, 2022
6103fa7
Merge branch 'main' of github.com:i-likecheese/pylint
Nov 18, 2022
0b3276b
[pre-commit.ci] auto fixes from pre-commit.com hooks
pre-commit-ci[bot] Nov 18, 2022
be2bffe
Merge branch 'PyCQA:main' into main
i-likecheese Nov 22, 2022
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3 changes: 3 additions & 0 deletions doc/whatsnew/fragments/5327.false_positive
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@@ -0,0 +1,3 @@
Don't emit ``used-before-assignment`` in pattern matching with a guard.

Closes #5327
5 changes: 5 additions & 0 deletions pylint/checkers/variables.py
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Expand Up @@ -30,6 +30,7 @@
)
from pylint.constants import (
PY39_PLUS,
PY310_PLUS,
TYPING_NEVER,
TYPING_NORETURN,
TYPING_TYPE_CHECKS_GUARDS,
Expand Down Expand Up @@ -1641,6 +1642,10 @@ def _check_consumer(
if not (
self._postponed_evaluation_enabled
and isinstance(stmt, (nodes.AnnAssign, nodes.FunctionDef))
) and not (
PY310_PLUS
and isinstance(stmt, nodes.Match)
and isinstance(node.parent, nodes.Compare)
Comment on lines +1698 to +1701
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This doesn't solve this false positive, because the .parent is nodes.Name:

match ("example", "one"):
    case (x, y) if x:  # <-- pylint complains about 'x' here
        print("woo!")
    case _:
        print("boo...")

):
self.add_message(
"used-before-assignment",
Expand Down
1 change: 1 addition & 0 deletions pylint/constants.py
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Expand Up @@ -18,6 +18,7 @@

PY38_PLUS = sys.version_info[:2] >= (3, 8)
PY39_PLUS = sys.version_info[:2] >= (3, 9)
PY310_PLUS = sys.version_info[:2] >= (3, 10)

IS_PYPY = platform.python_implementation() == "PyPy"

Expand Down