Use PEP 604 syntax wherever possible (#7493)

stdlib/multiprocessing/__init__.pyi

@@ -20,7 +20,7 @@ from multiprocessing.process import active_children as active_children, current_
 # multiprocessing.queues or the aliases defined below. See #4266 for discussion.
 from multiprocessing.queues import JoinableQueue as JoinableQueue, Queue as Queue, SimpleQueue as SimpleQueue
 from multiprocessing.spawn import freeze_support as freeze_support
-from typing import Any, Union, overload
+from typing import Any, overload
 from typing_extensions import Literal
 
 if sys.version_info >= (3, 8):
@@ -134,7 +134,7 @@ _SemaphoreType = synchronize.Semaphore
 # be identical (modulo self).
 
 # Synchronization primitives
-_LockLike = Union[synchronize.Lock, synchronize.RLock]
+_LockLike = synchronize.Lock | synchronize.RLock
 RawValue = context._default_context.RawValue
 RawArray = context._default_context.RawArray
 Value = context._default_context.Value

stdlib/multiprocessing/context.pyi

@@ -8,7 +8,7 @@ from multiprocessing import queues, synchronize
 from multiprocessing.pool import Pool as _Pool
 from multiprocessing.process import BaseProcess
 from multiprocessing.sharedctypes import SynchronizedArray, SynchronizedBase
-from typing import Any, ClassVar, TypeVar, Union, overload
+from typing import Any, ClassVar, TypeVar, overload
 from typing_extensions import Literal
 
 if sys.version_info >= (3, 8):
@@ -16,7 +16,7 @@ if sys.version_info >= (3, 8):
 else:
     __all__: list[str] = []
 
-_LockLike = Union[synchronize.Lock, synchronize.RLock]
+_LockLike = synchronize.Lock | synchronize.RLock
 _CT = TypeVar("_CT", bound=_CData)
 
 class ProcessError(Exception): ...

stdlib/multiprocessing/synchronize.pyi

@@ -3,11 +3,11 @@ import threading
 from contextlib import AbstractContextManager
 from multiprocessing.context import BaseContext
 from types import TracebackType
-from typing import Any, Callable, Union
+from typing import Any, Callable
 
 __all__ = ["Lock", "RLock", "Semaphore", "BoundedSemaphore", "Condition", "Event"]
 
-_LockLike = Union[Lock, RLock]
+_LockLike = Lock | RLock
 
 class Barrier(threading.Barrier):
     def __init__(