`used-before-assignment` false positive on multiple-target assignment

[xmo-odoo]

Bug description

When assigning to multiple target, and target n is used in target n+1, pylint flags the the line as E0601 "used-before-assignment", despite the statement being entirely correct per Python semantics:

# pylint: disable=missing-module-docstring, invalid-name
b = {}
a = b[id(a)] = 0

Even if there's an argument for flagging it (it's not great style), I don't think E0601 is valid.

Configuration

No response

Command used

`pylint <file>.py`

Pylint output

************* Module <file>
<file>.py:3:9: E0601: Using variable 'a' before assignment (used-before-assignment)

-----------------------------------------------------------------------
Your code has been rated at -15.00/10 (previous run: -25.00/10, +10.00)

Expected behavior

That the code passes, possibly triggers some sort of code style warning at most.

Pylint version

pylint 2.12.2
astroid 2.9.0
Python 3.8.12 (default, Sep 27 2021, 09:39:37)

OS / Environment

No response

Additional dependencies

No response

[Pierre-Sassoulas]

Thank you for opening the issue. I can reproduce on the main branch.

[tushar-deepsource]

Similar case:

x = [10]
y = 20
z, z[0] = x.copy(), y

[tushar-deepsource]

Do you think it's sufficient to suppress it if that variable is present before the current invocation in the assign targets in that same assign statements?

[Pierre-Sassoulas]

Could you provide an example @tushar-deepsource ?

[tusharsadhwani]

@Pierre-Sassoulas

where we are doing self.add_message("used-before-assignment"), we can check if there exists an AssignName node for the same variable in the same statement before it, and only raise the issue if there isn't one.

[Pierre-Sassoulas]

I meant a python example of what should raise or not :) (something that could become a functional tests if you will)

[tusharsadhwani]

@Pierre-Sassoulas

items = [10]
x = y = items[x] = 0  # Don't raise here

a, items[a] = 0, 20  # Don't raise here

print(b, c)  # Raise for `b` here

b = 10