[flxamartinez]

Before:

>>> lambda x: foo := 2
  File "<python-input-0>", line 1
    lambda x: foo := 2
    ^^^^^^^^^^^^^
SyntaxError: cannot use assignment expressions with lambda

After:

>>> lambda x: foo := 2
  File "<python-input-0>", line 1
    lambda x: foo := 2
              ^^^^^^^^
SyntaxError: cannot use named expression without parentheses here

The old message makes it look like you can't use := in a lambda, but you can if you add parentheses: lambda x: (foo := 2).

I added a rule for lambda ...: name := ... before the general one, so now it gives the same message as assert x := 1.

I also changed test_named_expression_invalid_15 because it was checking the old message.

This only fixes the lambda case. f(lambda: x := 1) still says "invalid syntax", and lambda x: foo.bar := 2 keeps the old message because parentheses don't fix that one. I saw that @brianschubert's idea in #146601 also covers this case.

• Issue: Misleading SyntaxError: cannot use assignment expressions with lambda #137570

[python-cla-bot]

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