False positive generalized unpacking detection with starred expression as assignment target

Starred expressions are allowed as assignment targets for Python < 3.5:

root@f1b4a742d8fc:/# python3.4
Python 3.4.10 (default, Mar 29 2019, 18:50:06)
[GCC 7.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> *x, y = [1, 2, 3]
>>> x
[1, 2]
>>> y
3
>>> z = *x, y
  File "<stdin>", line 1
SyntaxError: can use starred expression only as assignment target

Currently vermin falsely report this case as 3.5+:

>>> vermin.detect('*x, y = [1, 2, 3]')
[None, (3, 5)]

Maybe we need to mark some flags such as self.__seen_assign_target in visit_Assign and treat the targets attribute specially.

Environment

• Vermin version 1.0.3

[gousaiyang]

Three issues:

1. Assignment target with starred expression could also appear at for loops and comprehensions:

for *x, in [[1]]: pass
[x for *x, in [[1]]]  # also dict, set, generator comprehensions

1. Starred items may be deeply nested (not just direct child nodes as processed by ast.iter_child_nodes):

([x, *y], z) = ((1, 2), 3)

1. Suppressing detection for assignment targets also incorrectly suppressed detection for the expression part (right value):

*x, y = *u, *v

[netromdk]

Great. It’s merged. Thanks again!