test also custom key+getitem class

Author: randolf-scholz

test-data/unit/check-kwargs.test

@@ -572,13 +572,29 @@ main:41: error: Argument 1 to "foo" has incompatible type "**dict[str, str]"; ex
 [builtins fixtures/dict.pyi]
 
 [case testLiteralKwargs]
-from typing import Literal
+from typing import Literal, Mapping, Iterable
 def func(a: int, b: int) -> None: ...
 
+class GOOD_KW:
+    def keys(self) -> Iterable[Literal["a", "b"]]: ...
+    def __getitem__(self, key: str) -> int: ...
+
+class BAD_KW:
+    def keys(self) -> Iterable[Literal["one", 1]]: ...
+    def __getitem__(self, key: str) -> int: ...
+
 def test(
-    good_kw: dict[Literal["a", "b"], int],
-    bad_kw: dict[Literal["one", 1], int],
+    good_kw: GOOD_KW,
+    bad_kw: BAD_KW,
+    good_dict: dict[Literal["a", "b"], int],
+    bad_dict: dict[Literal["one", 1], int],
+    good_mapping: Mapping[Literal["a", "b"], int],
+    bad_mapping: Mapping[Literal["one", 1], int],
 ) -> None:
     func(**good_kw)
     func(**bad_kw)  # E: Argument after ** must have string keys
+    func(**good_dict)
+    func(**bad_dict)  # E: Argument after ** must have string keys
+    func(**good_mapping)
+    func(**bad_mapping)  # E: Argument after ** must have string keys
 [builtins fixtures/dict.pyi]