Use TypeAlias where possible for type aliases (#7630)

stdlib/shutil.pyi

@@ -2,6 +2,7 @@ import os
 import sys
 from _typeshed import BytesPath, StrOrBytesPath, StrPath, SupportsRead, SupportsWrite
 from typing import Any, AnyStr, Callable, Iterable, NamedTuple, Sequence, TypeVar, overload
+from typing_extensions import TypeAlias
 
 __all__ = [
     "copyfileobj",
@@ -82,7 +83,7 @@ else:
 
 def rmtree(path: StrOrBytesPath, ignore_errors: bool = ..., onerror: Callable[[Any, Any, Any], Any] | None = ...) -> None: ...
 
-_CopyFn = Callable[[str, str], None] | Callable[[StrPath, StrPath], None]
+_CopyFn: TypeAlias = Callable[[str, str], None] | Callable[[StrPath, StrPath], None]
 
 # N.B. shutil.move appears to take bytes arguments, however,
 # this does not work when dst is (or is within) an existing directory.