bpo-38978: Implement __class_getitem__ for asyncio objects (GH-17491)

https://bugs.python.org/issue38978

Lib/asyncio/futures.py

@@ -103,6 +103,9 @@ class Future:
             context['source_traceback'] = self._source_traceback
         self._loop.call_exception_handler(context)
 
+    def __class_getitem__(cls, type):
+        return cls
+
     @property
     def _log_traceback(self):
         return self.__log_traceback

Lib/asyncio/queues.py

@@ -76,6 +76,9 @@ class Queue:
     def __str__(self):
         return f'<{type(self).__name__} {self._format()}>'
 
+    def __class_getitem__(cls, type):
+        return cls
+
     def _format(self):
         result = f'maxsize={self._maxsize!r}'
         if getattr(self, '_queue', None):

Lib/asyncio/tasks.py

@@ -175,6 +175,9 @@ class Task(futures._PyFuture):  # Inherit Python Task implementation
             self._loop.call_exception_handler(context)
         super().__del__()
 
+    def __class_getitem__(cls, type):
+        return cls
+
     def _repr_info(self):
         return base_tasks._task_repr_info(self)