Use the parent of the node when inferring aug assign nodes instead of the statement

In 19b5af02304e3339fdd2a26cfafc337960eeebce we added a check for `AugAssign` nodes
when inferring `Assign` values. Unfortunately the `infer_assign` function was also
used by `infer_assignname`, which meant that when trying to infer an `AssignName` node,
we were inferring its value as the result of the `AugAssign` inference, leading
to spurious false positives.

Close PyCQA/pylint#2911
Close PyCQA/pylint#3214

3 files changed, 25 insertions, 3 deletions

diff --git a/ChangeLog b/ChangeLog
index e1419a79..c54d321a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -12,6 +12,11 @@ Release Date: TBA
 
   Close #666
 
+* Use the parent of the node when inferring aug assign nodes instead of the statement
+
+  Close PyCQA/pylint#2911
+  Close PyCQA/pylint#3214
+
 * Added some functions to the ``brain_numpy_core_umath`` module
 
   Close PyCQA/pylint#3319
diff --git a/astroid/inference.py b/astroid/inference.py
index a563287d..9c613cfe 100644
--- a/astroid/inference.py
+++ b/astroid/inference.py
@@ -837,9 +837,8 @@ def infer_assign(self, context=None):
     """infer a AssignName/AssignAttr: need to inspect the RHS part of the
     assign node
     """
-    stmt = self.statement()
-    if isinstance(stmt, nodes.AugAssign):
-        return stmt.infer(context)
+    if isinstance(self.parent, nodes.AugAssign):
+        return self.parent.infer(context)
 
     stmts = list(self.assigned_stmts(context=context))
     return bases._infer_stmts(stmts, context)
diff --git a/tests/unittest_inference.py b/tests/unittest_inference.py
index a5ed96b1..008e3d1f 100644
--- a/tests/unittest_inference.py
+++ b/tests/unittest_inference.py
@@ -5516,5 +5516,23 @@ def test_recursion_error_inferring_builtin_containers():
     helpers.safe_infer(node.targets[0])
 
 
+def test_inferaugassign_picking_parent_instead_of_stmt():
+    code = """
+    from collections import namedtuple
+    SomeClass = namedtuple('SomeClass', ['name'])
+    items = [SomeClass(name='some name')]
+
+    some_str = ''
+    some_str += ', '.join(__(item) for item in items)
+    """
+    # item needs to be inferrd as `SomeClass` but it was inferred
+    # as a string because the entire `AugAssign` node was inferred
+    # as a string.
+    node = extract_node(code)
+    inferred = next(node.infer())
+    assert isinstance(inferred, Instance)
+    assert inferred.name == "SomeClass"
+
+
 if __name__ == "__main__":
     unittest.main()