Handle dict subclasses for dict-not-iterating checks

2 files changed, 27 insertions, 9 deletions

diff --git a/pylint/checkers/python3.py b/pylint/checkers/python3.py
index 315d2d7da..e1835a142 100644
--- a/pylint/checkers/python3.py
+++ b/pylint/checkers/python3.py
@@ -53,6 +53,12 @@ def _is_old_octal(literal):
     return None
 
 
+def _inferred_value_is_dict(value):
+    if isinstance(value, astroid.Dict):
+        return True
+    return isinstance(value, astroid.Instance) and 'dict' in value.basenames
+
+
 def _check_dict_node(node):
     inferred_types = set()
     try:
@@ -65,12 +71,7 @@ def _check_dict_node(node):
 
     if not inferred_types:
         return True
-    for elem in inferred_types:
-        if isinstance(elem, astroid.Dict):
-            return True
-        if isinstance(elem, astroid.Instance) and 'dict' in elem.basenames:
-            return True
-    return False
+    return any(_inferred_value_is_dict(value) for value in inferred_types)
 
 
 def _is_builtin(node):
@@ -802,7 +803,7 @@ class Python3Checker(checkers.BaseChecker):
                         self._warn_if_deprecated(node, inferred_receiver.name,
                                                  {node.func.attrname},
                                                  report_on_modules=False)
-                    if (isinstance(inferred_receiver, astroid.Dict)
+                    if (_inferred_value_is_dict(inferred_receiver)
                             and node.func.attrname in DICT_METHODS):
                         if not _in_iterating_context(node):
                             checker = 'dict-{}-not-iterating'.format(node.func.attrname)
diff --git a/pylint/test/unittest_checker_python3.py b/pylint/test/unittest_checker_python3.py
index 76b8adff7..327677ea0 100644
--- a/pylint/test/unittest_checker_python3.py
+++ b/pylint/test/unittest_checker_python3.py
@@ -181,17 +181,34 @@ class TestPython3Checker(testutils.CheckerTestCase):
             self.as_argument_to_callable_constructor_test(fxn, func)
 
     @python2_only
+    def test_dict_subclasses_methods_in_iterating_context(self):
+        iterating, not_iterating = astroid.extract_node('''
+        from __future__ import absolute_import
+        from collections import defaultdict
+        d = defaultdict(list)
+        a, b = d.keys() #@
+        x = d.keys() #@
+        ''')
+
+        with self.assertNoMessages():
+            self.checker.visit_call(iterating.value)
+
+        message = testutils.Message('dict-keys-not-iterating', node=not_iterating.value)
+        with self.assertAddsMessages(message):
+            self.checker.visit_call(not_iterating.value)
+
+    @python2_only
     def test_dict_methods_in_iterating_context(self):
         iterating_code = [
             'for x in {}: pass',
             '(x for x in {})',
             '[x for x in {}]',
             'func({})',
-            'a, b = {}'
+            'a, b = {}',
         ]
         non_iterating_code = [
             'x = __({}())',
-            '__({}())[0]'
+            '__({}())[0]',
         ]
 
         for method in ('keys', 'items', 'values'):