Prevent assigned global variables from being marked and treated as closure...

Prevent assigned global variables from being marked and treated as closure variables in generators and coroutines.
Closes #2613.

Cython/Compiler/ParseTreeTransforms.py

@@ -2677,7 +2677,7 @@ class CreateClosureClasses(CythonTransform):
         if node.is_generator:
             for scope in node.local_scope.iter_local_scopes():
                 for entry in scope.entries.values():
-                    if not entry.from_closure:
+                    if not (entry.from_closure or entry.is_pyglobal or entry.is_cglobal):
                         entry.in_closure = True
 
         from_closure, in_closure = self.find_entries_used_in_closures(node)

tests/run/async_globals.pyx

+# mode: run
+# tag: pep492, asyncfor, await, gh2613
+
+# Using C-globals in coroutines.
+
+
+cdef object py_retval
+
+
+async def test():
+    """
+    >>> t = test()
+    >>> try: t.send(None)
+    ... except StopIteration as ex:
+    ...     print(ex.args[0] if ex.args else None)
+    ... else: print("NOT STOPPED!")
+    None
+    """
+    global py_retval
+    py_retval = {'foo': 42}