Python: Add __aiter__ as a recognised iterator method.

python/ql/src/semmle/python/objects/ObjectAPI.qll

@@ -350,6 +350,8 @@ class ClassValue extends Value {
     predicate isIterable() {
         this.hasAttribute("__iter__")
         or
+        this.hasAttribute("__aiter__")
+        or
         this.hasAttribute("__getitem__")
     }
 

python/ql/test/3/query-tests/Statements/iter/NonIteratorInForLoop.expected

@@ -1 +1,2 @@
+| async_iterator.py:26:11:26:34 | For | $@ of class '$@' may be used in for-loop. | async_iterator.py:26:20:26:33 | ControlFlowNode for MissingAiter() | Non-iterator | async_iterator.py:13:1:13:19 | class MissingAiter | MissingAiter |
 | statements_test.py:34:5:34:19 | For | $@ of class '$@' may be used in for-loop. | statements_test.py:34:18:34:18 | ControlFlowNode for IntegerLiteral | Non-iterator | file://:0:0:0:0 | builtin-class int | int |

python/ql/test/3/query-tests/Statements/iter/async_iterator.py

@@ -0,0 +1,27 @@
+
+class AsyncIterator:
+    def __init__(self):
+        pass
+
+    def __aiter__(self):
+        return self
+
+    async def __anext__(self):
+        await asyncio.sleep(5)
+        return 1
+
+class MissingAiter:
+    def __init__(self, delay, to):
+        pass
+
+    async def __anext__(self):
+        await asyncio.sleep(5)
+        return 1
+
+async def good():
+    async for x in AsyncIterator():
+        yield x
+
+async def bad():
+    async for x in MissingAiter():
+        yield x