Add @type_check_only to stub-only private classes in stdlib (#14512)

stdlib/xml/dom/minidom.pyi

@@ -3,7 +3,7 @@ from _collections_abc import dict_keys, dict_values
 from _typeshed import Incomplete, ReadableBuffer, SupportsRead, SupportsWrite
 from collections.abc import Iterable, Sequence
 from types import TracebackType
-from typing import Any, ClassVar, Generic, Literal, NoReturn, Protocol, TypeVar, overload
+from typing import Any, ClassVar, Generic, Literal, NoReturn, Protocol, TypeVar, overload, type_check_only
 from typing_extensions import Self, TypeAlias
 from xml.dom.minicompat import EmptyNodeList, NodeList
 from xml.dom.xmlbuilder import DocumentLS, DOMImplementationLS
@@ -40,9 +40,11 @@ _ImportableNodeVar = TypeVar(
     | Notation,
 )
 
+@type_check_only
 class _DOMErrorHandler(Protocol):
     def handleError(self, error: Exception) -> bool: ...
 
+@type_check_only
 class _UserDataHandler(Protocol):
     def handle(self, operation: int, key: str, data: Any, src: Node, dst: Node) -> None: ...
 

stdlib/xml/etree/ElementInclude.pyi

@@ -1,7 +1,8 @@
 from _typeshed import FileDescriptorOrPath
-from typing import Final, Literal, Protocol, overload
+from typing import Final, Literal, Protocol, overload, type_check_only
 from xml.etree.ElementTree import Element
 
+@type_check_only
 class _Loader(Protocol):
     @overload
     def __call__(self, href: FileDescriptorOrPath, parse: Literal["xml"], encoding: str | None = None) -> Element: ...

stdlib/xml/etree/ElementTree.pyi

@@ -335,6 +335,7 @@ class C14NWriterTarget:
 # The target type is tricky, because the implementation doesn't
 # require any particular attribute to be present. This documents the attributes
 # that can be present, but uncommenting any of them would require them.
+@type_check_only
 class _Target(Protocol):
     # start: Callable[str, dict[str, str], Any] | None
     # end: Callable[[str], Any] | None

stdlib/xml/sax/__init__.pyi

@@ -1,7 +1,7 @@
 import sys
 from _typeshed import ReadableBuffer, StrPath, SupportsRead, _T_co
 from collections.abc import Iterable
-from typing import Protocol
+from typing import Protocol, type_check_only
 from typing_extensions import TypeAlias
 from xml.sax._exceptions import (
     SAXException as SAXException,
@@ -13,6 +13,7 @@ from xml.sax._exceptions import (
 from xml.sax.handler import ContentHandler as ContentHandler, ErrorHandler as ErrorHandler
 from xml.sax.xmlreader import InputSource as InputSource, XMLReader
 
+@type_check_only
 class _SupportsReadClose(SupportsRead[_T_co], Protocol[_T_co]):
     def close(self) -> None: ...