Mappings aren't accepted by reversed().

3 files changed, 82 insertions, 11 deletions

diff --git a/checkers/base.py b/checkers/base.py
index 12bc8b3..2ec6fe9 100644
--- a/checkers/base.py
+++ b/checkers/base.py
@@ -700,18 +700,33 @@ functions, methods
         except NoSuchArgumentError:
             self.add_message('missing-reversed-argument', node=node)
         else:
-            if not argument:
-                return
-
-            for methods in REVERSED_METHODS:
-                for meth in methods:
-                    try:
-                        argument.getattr(meth)
-                    except astroid.NotFoundError:
+            if argument is None:
+                # nothing was infered
+                return 
+
+            if isinstance(argument, astroid.Instance):
+                if (argument._proxied.name == 'dict' and 
+                    is_builtin_object(argument._proxied)):
+                     self.add_message('bad-reversed-sequence', node=node)
+                     return
+                elif any(ancestor.name == 'dict' and is_builtin_object(ancestor)
+                       for ancestor in argument._proxied.ancestors()):
+                    # mappings aren't accepted by reversed()
+                    self.add_message('bad-reversed-sequence', node=node)
+                    return
+
+                for methods in REVERSED_METHODS:
+                    for meth in methods:
+                        try:
+                            argument.getattr(meth)
+                        except astroid.NotFoundError:
+                            break
+                    else:
                         break
-                else:
-                    break
-            else:                 
+                else:                 
+                    self.add_message('bad-reversed-sequence', node=node)
+            elif not isinstance(argument, (astroid.List, astroid.Tuple)):
+                # everything else is not a proper sequence for reversed()
                 self.add_message('bad-reversed-sequence', node=node)
 
 class NameChecker(_BasicChecker):
diff --git a/test/input/func_bad_reversed_sequence.py b/test/input/func_bad_reversed_sequence.py
new file mode 100644
index 0000000..3bab9b9
--- /dev/null
+++ b/test/input/func_bad_reversed_sequence.py
@@ -0,0 +1,48 @@
+""" Checks that reversed() receive proper argument """
+
+# pylint: disable-msg=too-few-public-methods,no-self-use,incomplete-protocol
+__revision__ = 0
+
+class GoodReversed(object):
+    """ Implements __reversed__ """
+    def __reversed__(self):
+        return [1, 2, 3]
+
+class SecondGoodReversed(object):
+    """ Implements __len__ and __getitem__ """
+    def __len__(self):
+        return 3
+
+    def __getitem__(self, index):
+        return index
+
+class BadReversed(object):
+    """ implements only len() """
+    def __len__(self):
+        return 3
+
+class SecondBadReversed(object):
+    """ implements only __getitem__ """
+    def __getitem__(self, index):
+        return index
+
+class ThirdBadReversed(dict):
+    """ dict subclass """
+
+def test():
+    """ test function """
+    seq = reversed()
+    seq = reversed(None)
+    seq = reversed([1, 2, 3])
+    seq = reversed((1, 2, 3))
+    seq = reversed(set())
+    seq = reversed({'a': 1, 'b': 2})
+    seq = reversed(iter([1, 2, 3]))
+    seq = reversed(GoodReversed())
+    seq = reversed(SecondGoodReversed())
+    seq = reversed(BadReversed())
+    seq = reversed(SecondBadReversed())
+    seq = reversed(range(100))
+    seq = reversed(ThirdBadReversed())
+    seq = reversed(lambda: None)
+    return seq
diff --git a/test/messages/func_bad_reversed_sequence.txt b/test/messages/func_bad_reversed_sequence.txt
new file mode 100644
index 0000000..87771ac
--- /dev/null
+++ b/test/messages/func_bad_reversed_sequence.txt
@@ -0,0 +1,8 @@
+E: 34:test: Missing argument to reversed()

+E: 35:test: The first reversed() argument is not a sequence

+E: 38:test: The first reversed() argument is not a sequence

+E: 39:test: The first reversed() argument is not a sequence

+E: 43:test: The first reversed() argument is not a sequence

+E: 44:test: The first reversed() argument is not a sequence

+E: 46:test: The first reversed() argument is not a sequence

+E: 47:test: The first reversed() argument is not a sequence
\ No newline at end of file