add test for some cell confusion problems

Author: timfel

graalpython/com.oracle.graal.python.test/src/tests/test_generators.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2018, Oracle and/or its affiliates.
+# Copyright (c) 2018, 2019 Oracle and/or its affiliates.
 # Copyright (C) 1996-2017 Python Software Foundation
 #
 # Licensed under the PYTHON SOFTWARE FOUNDATION LICENSE VERSION 2
@@ -178,3 +178,46 @@ def func(*args):
     gen = (x for x in range(10))
     assert func(*lst) == set(lst)
     assert func(*gen) == set(lst)
+
+
+def test_generator_cell_confusion():
+    # tfel: this demonstrates various errors we can get when we get confused
+    # about the generator scopes and their parents for eager iterator
+    # evaluation. In fact, all of these should work
+    def unbound_local_l2():
+        l1 = []
+        l2 = []
+        return [
+            link for link in (
+                (url for url in l1),
+                (url for url in l2)
+            )
+        ]
+
+    assert len(unbound_local_l2()) == 2
+
+    def assertion_error_getting_closure_from_locals():
+        l1 = []
+        l2 = []
+        l3 = []
+        return [
+            link for link in (
+                (url for url in l1),
+                (url for url in l2),
+                (url for url in l3),
+            )
+        ]
+
+    assert len(assertion_error_getting_closure_from_locals()) == 3
+
+    def illegal_state_expected_cell_got_list():
+        l11, l1 = [], []
+        l22, l2 = [], []
+        return [
+            link for link in (
+                (url for url in l1),
+                (url for url in l2),
+            )
+        ]
+
+    assert len(illegal_state_expected_cell_got_list()) == 2