pylint-dev/pylint

Using return value of a function that returns None is not always reported.

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#10,476 建立於 2025年8月5日

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 (4 留言) (0 反應) (1 負責人)Python (4,978 star) (1,059 fork)batch import
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描述

Bug description

def f1(i: int) -> None:
    print(i)


def f2() -> None:
    r = f1(2)  # assignment-from-no-return
    if not r:
        print("error")
    if not f1(2):  # no error
        print("error")

Configuration

Command used

pylint experiments/type_test.py -E

Pylint output

experiments/type_test.py:6:4: E1111: Assigning result of a function call, where the function has no return (assignment-from-no-return)

Expected behavior

In the code snippet, line 6 will report an error, but line 9 doesn't. I'd expect to see an error on line 9, since the code essentially does the same thing. Not sure whether this is by design or a bug. If it's by design, feel free to change this issue to a feature request.

Pylint version

pylint 3.3.7
astroid 3.3.10
Python 3.13.5 (main, Jun 11 2025, 15:36:57) [Clang 17.0.0 (clang-1700.0.13.3)]

OS / Environment

MacOS 15.5

Additional dependencies

貢獻者指南

技術棧
python
領域
developer experience
議題類型
bug
難度面向新貢獻者的預計實作難度，1 表示很小改動，5 表示專家級工作。
2
預計時間有經驗貢獻者完成調查、實作、測試並準備 pull request 的粗略時間範圍。
1-3 hours
活動狀態議題目前的可參與程度：新鮮、活躍、陳舊、阻塞或等待維護者輸入。
blocked
清晰度議題是否清楚說明預期改動、驗收標準和下一步。
clear
前置要求
Python programmingFamiliarity with pylint internals
新手友善度1-100 的估計分數，表示該議題對首次貢獻者的友善程度。
70
研究方向
Start by examining the checker that raises 'assignment from no return' (likely in pylint/checkers/typecheck.py). Look at the detection logic: it currently catches assignments (e.g., `r = f1(2)`) but misses cases where the function call is used directly in a condition (e.g., `if not f1(2):`). Search for existing tests related to this warning and understand how the checker processes function call expressions. Consider extending the check to cover any expression that uses the return value of a None returning function, not just explicit assignments.