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RUF057 fix introduces an error when the argument contains a newline #15598

@dscorbett

Description

@dscorbett

The fix for unnecessary-round (RUF057) in Ruff 0.9.2 can introduce a syntax error or change behavior when the argument to round contains a newline.

Here is a crash:

$ cat ruf057_1.py
round(-
1)

$ ruff --isolated check --fix --preview --select RUF057 ruf057_1.py

error: Fix introduced a syntax error. Reverting all changes.

This indicates a bug in Ruff. If you could open an issue at:

    https://github.com/astral-sh/ruff/issues/new?title=%5BFix%20error%5D

...quoting the contents of `ruf057_1.py`, the rule codes RUF057, along with the `pyproject.toml` settings and executed command, we'd be very appreciative!

ruf057_1.py:1:1: RUF057 Value being rounded is already an integer
  |
1 | / round(-
2 | | 1)
  | |__^ RUF057
  |
  = help: Remove unnecessary `round` call

Found 1 error.
[*] 1 fixable with the `--fix` option.

Here is a syntax error:

$ cat ruf057_2.py
round(1
* 1)

$ ruff --isolated check --fix --preview --select RUF057 ruf057_2.py
Found 1 error (1 fixed, 0 remaining).

$ cat ruf057_2.py
1
* 1

$ python ruf057_2.py
  File "ruf057_2.py", line 2
    * 1
    ^^^
SyntaxError: can't use starred expression here

Here is a runtime behavior change:

$ cat ruf057_3.py
x = round(1
+ 1)
print(x)

$ python ruf057_3.py
2

$ ruff --isolated check --fix --preview --select RUF057 ruf057_3.py
Found 1 error (1 fixed, 0 remaining).

$ cat ruf057_3.py
x = 1
+ 1
print(x)

$ python ruf057_3.py
1

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