The backwards tokenizer sometimes parsed not only string literals but also normal names.

jedi/parser/user_context.py

@@ -104,7 +104,8 @@ class UserContext(object):
                 # The same is true for string prefixes -> represented as a
                 # combination of string and name.
                 if tok_type == tokenize.NUMBER and tok_str[-1] == '.' \
-                        or tok_type == tokenize.NAME and last_type == tokenize.STRING:
+                        or tok_type == tokenize.NAME and last_type == tokenize.STRING \
+                        and tok_str.lower() in ('b', 'u', 'r', 'br', 'ur'):
                     force_point = False
                 else:
                     break

test/test_api/test_call_signatures.py

@@ -209,6 +209,13 @@ class TestCallSignatures(TestCase):
 
         self._run(source, 'test2', 0)
 
+    def test_return(self):
+        source = dedent('''
+        def foo():
+            return '.'.join()''')
+
+        self._run(source, 'join', 0, column=len("    return '.'.join("))
+
 
 class TestParams(TestCase):
     def params(self, source, line=None, column=None):