Fix a crash when inferring subscripts which returned the same object all the time.

2 files changed, 20 insertions, 4 deletions

diff --git a/astroid/inference.py b/astroid/inference.py
index 148c8cd..db80e43 100644
--- a/astroid/inference.py
+++ b/astroid/inference.py
@@ -227,6 +227,7 @@ def _slice_value(index, context=None):
     return _SLICE_SENTINEL
 
 
+@bases.raise_if_nothing_inferred
 def infer_subscript(self, context=None):
     """Inference for subscripts
 
@@ -276,7 +277,7 @@ def infer_subscript(self, context=None):
         yield inferred
 
 nodes.Subscript._infer = bases.path_wrapper(infer_subscript)
-nodes.Subscript.infer_lhs = bases.raise_if_nothing_inferred(infer_subscript)
+nodes.Subscript.infer_lhs = infer_subscript
 
 
 @bases.raise_if_nothing_inferred
@@ -388,6 +389,7 @@ def _infer_unaryop(self, context=None):
                     yield util.YES
 
 
+@bases.raise_if_nothing_inferred
 @bases.path_wrapper
 def infer_unaryop(self, context=None):
     """Infer what an UnaryOp should return when evaluated."""
@@ -395,7 +397,7 @@ def infer_unaryop(self, context=None):
                                     exceptions.UnaryOperationError)
 
 nodes.UnaryOp._infer_unaryop = _infer_unaryop
-nodes.UnaryOp._infer = bases.raise_if_nothing_inferred(infer_unaryop)
+nodes.UnaryOp._infer = infer_unaryop
 
 
 def _is_not_implemented(const):
@@ -600,13 +602,14 @@ def _infer_binop(self, context):
                 yield result
 
 
+@bases.yes_if_nothing_inferred
 @bases.path_wrapper
 def infer_binop(self, context=None):
     return _filter_operation_errors(self, _infer_binop, context,
                                     exceptions.BinaryOperationError)
 
 nodes.BinOp._infer_binop = _infer_binop
-nodes.BinOp._infer = bases.yes_if_nothing_inferred(infer_binop)
+nodes.BinOp._infer = infer_binop
 
 
 def _infer_augassign(self, context=None):
diff --git a/astroid/tests/unittest_inference.py b/astroid/tests/unittest_inference.py
index bc75f9d..ef0886f 100644
--- a/astroid/tests/unittest_inference.py
+++ b/astroid/tests/unittest_inference.py
@@ -30,6 +30,7 @@ from astroid.builder import parse
 from astroid.inference import infer_end as inference_infer_end
 from astroid.bases import Instance, BoundMethod, UnboundMethod,\
                                 path_wrapper, BUILTINS
+from astroid import helpers
 from astroid import objects
 from astroid import test_utils
 from astroid import util
@@ -2961,7 +2962,19 @@ class InferenceTest(resources.SysPathSetup, unittest.TestCase):
        author = next(inferred.igetattr('author'))
        self.assertIsInstance(author, nodes.Const)
        self.assertEqual(author.value, 'Rushdie')
-        
+
+    def test_subscript_inference_error(self):
+       # Used to raise StopIteration
+       ast_node = test_utils.extract_node('''
+       class AttributeDict(dict):
+           def __getitem__(self, name):
+               return self
+       flow = AttributeDict()
+       flow['app'] = AttributeDict()
+       flow['app']['config'] = AttributeDict()
+       flow['app']['config']['doffing'] = AttributeDict() #@
+       ''')
+       self.assertIsNone(helpers.safe_infer(ast_node.targets[0]))
 
 
 class GetattrTest(unittest.TestCase):