Loosen Mapping.update() overloads a little (#14593)

stdlib/@tests/test_cases/builtins/check_dict.py

@@ -4,6 +4,10 @@ import os
 from typing import Any, Dict, Generic, Iterable, Mapping, TypeVar, Union
 from typing_extensions import Self, assert_type
 
+###################################################################
+# Note: tests for `dict.update()` are in `check_MutableMapping.py`.
+###################################################################
+
 # These do follow `__init__` overloads order:
 # mypy and pyright have different opinions about this one:
 # mypy raises: 'Need type annotation for "bad"'

stdlib/@tests/test_cases/typing/check_MutableMapping.py

@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-from typing import Any, Union
+from typing import Any, Hashable, Sequence, Union
 from typing_extensions import assert_type
 
 
@@ -30,6 +30,15 @@ def check_update_method__str_key() -> None:
     d.update([("", "")])  # type: ignore
 
 
+def test_keywords_allowed_on_dict_update_where_key_type_is_str_supertype(
+    a: dict[object, Any], b: dict[Hashable, Any], c: dict[Sequence[str], Any], d: dict[str, Any]
+) -> None:
+    a.update(keyword_args_are_accepted="whatever")
+    b.update(here_too="whooo")
+    c.update(and_here="hooray")
+    d.update(also_here="yay")
+
+
 def check_setdefault_method() -> None:
     d: dict[int, str] = {}
     d2: dict[int, str | None] = {}