E0112: too-many-star-expressions triggers on valid code

[njsmith]

Steps to reproduce

Here's some legal python code:

(a, *b), *c = ((1, 2, 3), 4, 5)
print(a)  # 1
print(b)  # (2, 3)
print(c)  # (4, 5)

For example, this can be used to unpack the complicated return value from socket.getaddrinfo.

Current behavior

Running pylint on the above code reports E0112: too-many-star-expressions:

/tmp/stars.py:1:0: E0112: More than one starred expression in assignment (too-many-star-expressions)

Expected behavior

Don't report this error on valid code.

pylint --version output

pylint 2.1.1
astroid 2.0.4
Python 3.6.5 (default, Apr  1 2018, 05:46:30) 
[GCC 7.3.0]

[njsmith]

Not that anyone asked me, but if that commit were a PR I was reviewing, I'd also have added tests for

(*a, *b), c = ...    # should trigger a message
((*a, b), *c), *d = ... # shouldn't trigger a message

And I'm pretty sure the second test would fail, because the fix as written seems to hardcode exactly one level of traversal and then revert to the old buggy behavior.

[PCManticore]

Thanks for the suggestion though! I'll take a look tomorrow for making that code handle more traversal levels.