Don't crash when getting the string representation of BadUnaryOperationMessage

In some cases, when the operand does not have a .name attribute,
getting the string representation of a BadUnaryOperationMessage leads
to a crash.

Close PyCQA/pylint#1563

3 files changed, 41 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index 74401949..1dee67af 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,16 @@
 Change log for the astroid package (used to be astng)
 =====================================================
 
+--
+
+   * Don't crash when getting the string representation of BadUnaryOperationMessage
+
+     In some cases, when the operand does not have a .name attribute,
+     getting the string representation of a BadUnaryOperationMessage leads
+     to a crash.
+
+     Close PyCQA/pylint#1563
+
 2017-06-03 -- 1.5.3
 
     * enum34 dependency is forced to be at least version 1.1.3. Fixes spurious
diff --git a/astroid/tests/unittest_inference.py b/astroid/tests/unittest_inference.py
index 9a12e322..ebf2ece7 100644
--- a/astroid/tests/unittest_inference.py
+++ b/astroid/tests/unittest_inference.py
@@ -2334,6 +2334,15 @@ class InferenceTest(resources.SysPathSetup, unittest.TestCase):
             self.assertEqual(len(errors), 1, (expected, node))
             self.assertEqual(str(errors[0]), expected_value)
 
+    def test_unary_type_errors_for_non_instance_objects(self):
+        node = extract_node('~slice(1, 2, 3)')
+        errors = node.type_errors()
+        self.assertEqual(len(errors), 1)
+        self.assertEqual(
+            str(errors[0]),
+            'bad operand type for unary ~: slice'
+        )
+
     def test_bool_value_recursive(self):
         pairs = [
             ('{}', False),
diff --git a/astroid/util.py b/astroid/util.py
index 6d2d0177..6fd52d31 100644
--- a/astroid/util.py
+++ b/astroid/util.py
@@ -74,8 +74,29 @@ class BadUnaryOperationMessage(BadOperationMessage):
         self.op = op
         self.error = error
 
+    @property
+    def _object_type_helper(self):
+        helpers = lazy_import('helpers')
+        return helpers.object_type
+
+    def _object_type(self, obj):
+        objtype = self._object_type_helper(obj)
+        if objtype is Uninferable:
+            return None
+
+        return objtype
+
     def __str__(self):
-        operand_type = self.operand.name
+        if hasattr(self.operand, 'name'):
+            operand_type = self.operand.name
+        else:
+            object_type = self._object_type(self.operand)
+            if hasattr(object_type, 'name'):
+                operand_type = object_type.name
+            else:
+                # Just fallback to as_string
+                operand_type = object_type.as_string()
+
         msg = "bad operand type for unary {}: {}"
         return msg.format(self.op, operand_type)