gh-91896: Improve visibility of ByteString deprecation warnings (#104294)

Lib/typing.py

@@ -1599,6 +1599,22 @@ class _SpecialGenericAlias(_NotIterable, _BaseGenericAlias, _root=True):
     def __ror__(self, left):
         return Union[left, self]
 
+
+class _DeprecatedGenericAlias(_SpecialGenericAlias, _root=True):
+    def __init__(
+        self, origin, nparams, *, removal_version, inst=True, name=None
+    ):
+        super().__init__(origin, nparams, inst=inst, name=name)
+        self._removal_version = removal_version
+
+    def __instancecheck__(self, inst):
+        import warnings
+        warnings._deprecated(
+            f"{self.__module__}.{self._name}", remove=self._removal_version
+        )
+        return super().__instancecheck__(inst)
+
+
 class _CallableGenericAlias(_NotIterable, _GenericAlias, _root=True):
     def __repr__(self):
         assert self._name == 'Callable'
@@ -2756,7 +2772,6 @@ Mapping = _alias(collections.abc.Mapping, 2)
 MutableMapping = _alias(collections.abc.MutableMapping, 2)
 Sequence = _alias(collections.abc.Sequence, 1)
 MutableSequence = _alias(collections.abc.MutableSequence, 1)
-ByteString = _alias(collections.abc.ByteString, 0)  # Not generic
 # Tuple accepts variable number of parameters.
 Tuple = _TupleType(tuple, -1, inst=False, name='Tuple')
 Tuple.__doc__ = \
@@ -3556,3 +3571,18 @@ def override(method: F, /) -> F:
         # read-only property, TypeError if it's a builtin class.
         pass
     return method
+
+
+def __getattr__(attr):
+    if attr == "ByteString":
+        import warnings
+        warnings._deprecated("typing.ByteString", remove=(3, 14))
+        with warnings.catch_warnings(
+            action="ignore", category=DeprecationWarning
+        ):
+            # Not generic
+            ByteString = globals()["ByteString"] = _DeprecatedGenericAlias(
+                collections.abc.ByteString, 0, removal_version=(3, 14)
+            )
+        return ByteString
+    raise AttributeError(f"module 'typing' has no attribute {attr!r}")