Pylint incorrectly flags as `unused-import` things that are used in string literal type annotations

[sanyassh]

Steps to reproduce

pylint_example.py:

class Class:
    pass

pylint_example2.py:

from pylint_example import Class


class Class2:
    cls: 'Class'

pylint pylint_example2.py

************* Module pylint_example2
pylint_example2.py:4:0: R0903: Too few public methods (0/2) (too-few-public-methods)
pylint_example2.py:1:0: W0611: Unused Class imported from pylint_example (unused-import)

------------------------------------------------------------------
Your code has been rated at 3.33/10 (previous run: 3.33/10, +0.00)

Current behavior

String literal in type annotation is considered "unused" and warning is emitted.

Expected behavior

There should not be any warning about unused import.

pylint --version output

pylint 2.4.4
astroid 2.3.3
Python 3.6.9 (default, Nov 7 2019, 10:44:02)
[GCC 8.3.0]

[jnsnow]

I have some additional information related to this issue.

Even though there are workarounds by using e.g.

from __future__ import annotations

there are some type definitions that actually still require you to use string quoting, because typeshed expresses some types as subscriptable generics, e.g. os.PathLike must be expressed as 'os.PathLike[str]' -- the quotes are a requirement, because this type cannot be subscripted at runtime.

Sadly, every other CQA tool also fails here: pyflakes and pycharm both do not understand this annotation and all three tools have different silencing methods.

[vbraun]

Flake8 can do it for the record, and does not emit an F401 on the example:

# flake8 pylint_example2.py
# echo $?
0

[dmtucker]

#4315 also reproduces when the type is a string.