From 37dac96e7980217bd0e6cd6f736af73a741e4ac8 Mon Sep 17 00:00:00 2001
From: Sergei Lebedev <slebedev@google.com>
Date: Tue, 22 Jun 2021 11:36:58 +0100
Subject: [PATCH] VariableChecker now accounts for attribute lookups in type
 comments

Prior to this commit VariableChecker did not recurse into attribute lookups
in type comments. This lead to false positive unused-import messages in e.g.

    import collections
    d = ...  # type: collections.OrderedDict

Fixes #4603.
---
 CONTRIBUTORS.txt                     |  2 ++
 ChangeLog                            |  5 +++++
 pylint/checkers/variables.py         |  4 ++++
 tests/checkers/unittest_variables.py | 13 +++++++++++++
 4 files changed, 24 insertions(+)

diff --git a/CONTRIBUTORS.txt b/CONTRIBUTORS.txt
index b1de7ff30e3..05e4a31e18e 100644
--- a/CONTRIBUTORS.txt
+++ b/CONTRIBUTORS.txt
@@ -503,3 +503,5 @@ contributors:
 * Markus Siebenhaar: contributor
 
 * Lorena Buciu (lorena-b): contributor
+
+* Sergei Lebedev (superbobry): contributor
diff --git a/ChangeLog b/ChangeLog
index c2b1382d7a8..4ffa5a84144 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -171,6 +171,11 @@ Closes #4555
 
   Closes #4023
 
+* Fix ``unused-import`` false positive for imported modules referenced in
+  attribute lookups in type comments.
+
+  Closes #4603
+
 
 What's New in Pylint 2.8.3?
 ===========================
diff --git a/pylint/checkers/variables.py b/pylint/checkers/variables.py
index 3ddafd59942..8a46375097a 100644
--- a/pylint/checkers/variables.py
+++ b/pylint/checkers/variables.py
@@ -1826,6 +1826,10 @@ def _store_type_annotation_node(self, type_annotation):
             self._type_annotation_names.append(type_annotation.name)
             return
 
+        if isinstance(type_annotation, astroid.Attribute):
+            self._store_type_annotation_node(type_annotation.expr)
+            return
+
         if not isinstance(type_annotation, astroid.Subscript):
             return
 
diff --git a/tests/checkers/unittest_variables.py b/tests/checkers/unittest_variables.py
index 90daa8d5d10..83321994532 100644
--- a/tests/checkers/unittest_variables.py
+++ b/tests/checkers/unittest_variables.py
@@ -191,6 +191,19 @@ def my_method(self) -> MyType:
         with self.assertNoMessages():
             self.walk(module)
 
+    def test_attribute_in_type_comment(self):
+        """Ensure attribute lookups in type comments are accounted for.
+
+        https://github.com/PyCQA/pylint/issues/4603
+        """
+        module = astroid.parse(
+            """
+        import abc
+        x = ... # type: abc.ABC
+        """)
+        with self.assertNoMessages():
+            self.walk(module)
+
 
 class TestVariablesCheckerWithTearDown(CheckerTestCase):