Add rule to detect potential bug caused by unheld references to asyncio.create_task

Feature

Hi there,

I wanted to suggest adding a rule to MyPy to help detect a potential bug that can occur when using asyncio.create_task. If a developer doesn't hold a reference to the task object returned by create_task, the task may disappear without warning when Python runs garbage collection. This can lead to unpredictable failures in the code, which can be extremely difficult to debug.

References:
https://textual.textualize.io/blog/2023/02/11/the-heisenbug-lurking-in-your-async-code/
https://news.ycombinator.com/item?id=34754276

Pitch

I think adding a rule to MyPy that flags code which creates an asyncio task but doesn't hold a reference to it would be very helpful in preventing this bug from occurring. It would alert developers to the fact that they need to make sure they're holding a reference to the task object if they want to avoid this problem.

Commencez par examiner la gestion actuelle de asyncio.create_task par mypy ainsi que les rapports liés décrivant des tâches qui ne sont pas conservées. Définissez quels modèles de références non conservées la règle proposée doit signaler, comment les diagnostics doivent apparaître et quels cas de test établissent que la règle est complète.