[Fix error] C417 and walrus statements

[zeevox]

Applying fixes for rule C417 introduces a syntax error when the second map argument is a walrus assignment operator.

Minimal example below.
I'm using ruff 0.8.2 and Python 3.12.7 to test this.
For a more complete example, this issue first arose in my solution to Advent of Code 2019 Day 3.

a = [1, 2, 3]
b = map(lambda x: x, c := a)
print(c)

Fix applied by ruff check test.py --select C417 --fix --unsafe-fixes

-b = map(lambda x: x, c := a)
+b = (x for x in c := a)

is syntactically incorrect

  File "/home/zeevox/test.py", line 2
    b = (x for x in c := a)
                      ^^
SyntaxError: invalid syntax

You would think wrapping the walrus statement in parentheses would suffice, like

b = (x for x in (c := a))

And indeed, ruff believes all is well

% ruff check test.py --select C417
All checks passed!

but this too, in fact, raises a syntax error

  File "/home/zeevox/test.py", line 2
    b = (x for x in (c := a))
                     ^^^^^^
SyntaxError: assignment expression cannot be used in a comprehension iterable expression

I wonder whether the real solution is to extract the assignment onto the previous line, or not show the warning in the first place.