Make more miscellaneous fields read-only, annotate _json.make_encoder (#7439)

stdlib/asyncio/futures.pyi

@@ -2,7 +2,7 @@ import sys
 from _typeshed import Self
 from concurrent.futures._base import Error, Future as _ConcurrentFuture
 from typing import Any, Awaitable, Callable, Generator, Iterable, TypeVar
-from typing_extensions import TypeGuard
+from typing_extensions import Literal, TypeGuard
 
 from .events import AbstractEventLoop
 
@@ -42,9 +42,13 @@ if sys.version_info < (3, 7):
 
 class Future(Awaitable[_T], Iterable[_T]):
     _state: str
-    _exception: BaseException
+    @property
+    def _exception(self) -> BaseException: ...
     _blocking: bool
-    _log_traceback: bool
+    @property
+    def _log_traceback(self) -> bool: ...
+    @_log_traceback.setter
+    def _log_traceback(self, val: Literal[False]) -> None: ...
     _asyncio_future_blocking: bool  # is a part of duck-typing contract for `Future`
     def __init__(self, *, loop: AbstractEventLoop | None = ...) -> None: ...
     def __del__(self) -> None: ...