Separate check for possibly unused arguments if locals() is used

[Stealthii]

Current problem

• I have a long list of keywords to a method, that I want to define for type hints
• I need to pass these to another method as a dictionary, using locals()
• pylint detects possibly unused variables, but not arguments

Desired solution

• pylint should extend the logic used around unused argument and variable definitions to consider arguments as potentially unused as well

Additional context

Here is an example function that makes use of local scope variables and arguments.

def example(arg_a='a', arg_b='b'):  # unused-argument
    """An example function."""
    var_c = 'c'  # potentially-unused-variable
    return locals()  # {'arg_a': 'a', 'arg_b': 'b', 'var_c': 'c'}

[Stealthii]

This is related to #1909, which implemented a check for potentially unused variables. Arguments to a function/method do not fall under this check.

I believe for consistency that a 'possibly-unused-argument' check should exist similar to 'potentially-unused-variable', regardless of opinion about locals() use.

[Pierre-Sassoulas]

It makes sense thank you for opening the issue.

[bersbersbers]

Here's an example summarizing the missing consistency with (possibly-)unused-variable:

"""Demonstrate use case of *possibly* unused argument."""

def _fun1():
    var = 1  # pylint:disable=unused-variable

def _fun2():
    var = 1  # pylint:disable=possibly-unused-variable # note "possibly"!
    return locals()

def _fun3(arg=1):  # pylint:disable=unused-argument
    pass

def _fun4(arg=1):  # this should be a *possibly*-unused-argument
    return locals()