Misleading SyntaxError: cannot use assignment expressions with lambda

Bug report

Bug description:

Python 3.12.8 (tags/v3.12.8:2dc476b, Dec  3 2024, 19:30:04) [MSC v.1942 64 bit (AMD64)] on win32
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>>> lambda x: foo := 2
  File "<stdin>", line 1
    lambda x: foo := 2
    ^^^^^^^^^^^^^
SyntaxError: cannot use assignment expressions with lambda
>>> lambda x: (foo := 2)
<function <lambda> at 0x00000229CC40E0C0>

IIRC, until today I believed that you could never use an assignment expression in a lambda. I was disabused of this notion only by reading PEP 572 itself. I believe the SyntaxError should ideally read something along the lines of "cannot use unparenthesized assignment expressions with lambda".

I wasn't sure to what category to file this under exactly, sorry if I chose wrong.

CPython versions tested on:

3.12

Operating systems tested on:

Windows

Commencez par rechercher dans CPython le diagnostic exact "cannot use assignment expressions with lambda" et examinez la gestion correspondante dans le parseur ou le compilateur, avec PEP 572 comme contexte. Reproduisez les deux exemples de lambda du rapport ; le travail est terminé lorsque la forme non parenthésée signale la restriction plus précise, tandis que la forme parenthésée continue de fonctionner.