Support weakref on the Future class.

src/async_kernel/caller.py

@@ -53,6 +53,7 @@ class Future(Awaitable[T]):
     """
 
     __slots__ = [
+        "__weakref__",
         "_anyio_event_done",
         "_cancel_scope",
         "_cancelled",
@@ -64,6 +65,8 @@ class Future(Awaitable[T]):
         "thread",
     ]
     _result: T
+    thread: threading.Thread
+    "The thread in which the result is targeted to run."
 
     def __init__(self, thread: threading.Thread | None = None) -> None:
         self._event_done = threading.Event()

tests/test_caller.py

@@ -3,6 +3,7 @@
 import inspect
 import threading
 import time
+import weakref
 from contextvars import ContextVar
 from random import random
 from typing import Literal, cast
@@ -30,6 +31,10 @@ def transport(request):
 
 @pytest.mark.anyio
 class TestFuture:
+    def test_weakref(self):
+        f = Future()
+        assert weakref.ref(f)() is f
+
     async def test_set_and_wait_result(self):
         fut = Future[int]()
         assert inspect.isawaitable(fut)