Add test for async list comprehension

Author: markshannon

Lib/test/test_coroutines.py

@@ -2265,6 +2265,30 @@ def c():
         # before fixing, visible stack from throw would be shorter than from send.
         self.assertEqual(len_send, len_throw)
 
+    def test_call_aiter_once_in_comprehension(self):
+
+        class Iterator:
+
+            def __init__(self):
+                self.val = 0
+
+            async def __anext__(self):
+                if self.val == 2:
+                    raise StopAsyncIteration
+                self.val += 1
+                return self.val
+
+            # No __aiter__ method
+
+        class C:
+
+            def __aiter__(self):
+                return Iterator()
+
+        async def run():
+            return [i async for i in C()]
+
+        self.assertEqual(run_async(run()), ([], [1,2]))
 
 @unittest.skipIf(
     support.is_emscripten or support.is_wasi,