False positive unnecessary-comprehension when modifying a dict to a list of tuples

[martimlobao]

Steps to reproduce

Given a file a.py:

def main():
    mydict = {"foo": 1, "bar": 2}
    return [(k, v) for k, v in mydict.items()]

Pylint will complain about an unnecessary comprehension, even though the comprehension is modifying the type from a dictionary to a list of tuples.

Current behavior

Result of pylint a.py:

$ pylint a.py 
************* Module example
example.py:3:0: R1721: Unnecessary use of a comprehension (unnecessary-comprehension)

Expected behavior

No errors.

pylint --version output

Result of pylint --version output:

$ pylint --version output
pylint 2.8.2
astroid 2.5.6
Python 3.8.7 (default, Jan 22 2021, 22:54:27) 
[Clang 12.0.0 (clang-1200.0.32.28)]

EDIT: I guess alternatively it might be cleaner to use list(mydict.items()) instead. That feels like it might be a separate issue altogether, and I'm not sure if there aren't other false positives that can't be solved similarly. It's not that the comprehension is unnecessary, it's that there's a nicer way to do it. Maybe a new warning might also be a good idea?

[Pierre-Sassoulas]

Thank you for opening the issue !

[cdce8p]

I think this is more a case of a misleading error message that could be improved. As you pointed out list(mydict.items()) is indeed equivalent and IMO the better solution. So technically this is an unnecessary-comprehension.

I can't remember the exact code, but I had something similar happen a while back where it took me more than a short moment to figure out a solution.

[yushao2]

Proposing an improvement to helptext for this checker in my PR, please take a look :)

[yushao2]

@Pierre-Sassoulas is it possible to assign this to me since I've already started some work on it?

Thanks!