Fix typing for MapKeysView

Summary: Addressing the `pyre-ignore` for `.keys()`.

Reviewed By: createdbysk

Differential Revision: D66439015

fbshipit-source-id: 2a06cf0ae8e63229311b9efd0e1f48774ddfc356

third-party/thrift/src/thrift/lib/python/mutable_containers.pyi

@@ -17,7 +17,8 @@
 import typing
 from collections.abc import (
     Iterator,
-    MutableMapping as MutableMappingAbc,
+    KeysView,
+    MutableMapping,
     MutableSequence,
     MutableSet as MutableSetAbc,
 )
@@ -203,7 +204,7 @@ class SupportsKeysAndGetItem(Protocol[K, V]):
     def keys(self) -> Iterable[K]: ...
     def __getitem__(self, k: K) -> V: ...
 
-class MutableMap(MutableMappingAbc[K, V]):
+class MutableMap(MutableMapping[K, V]):
     def __init__(
         self,
         key_typeinfo: object,
@@ -255,7 +256,6 @@ class MutableMap(MutableMappingAbc[K, V]):
     def pop(self, key: K, /, default: T) -> V | T: ...
     def popitem(self) -> Tuple[K, V]: ...
     def clear(self) -> None: ...
-    # pyre-ignore[15]: Inconsistent override
     def keys(self) -> MapKeysView[K]: ...
     # pyre-ignore[15]: Inconsistent override
     def items(self) -> MapItemsView[K, V]: ...
@@ -283,10 +283,13 @@ class MutableMap(MutableMappingAbc[K, V]):
         /,
     ) -> V: ...
 
-class MapKeysView(Generic[K]):
+class MapKeysView(KeysView[K]):
     def __len__(self) -> int: ...
     def __contains__(self, key: object) -> bool: ...
-    def __iter__(self) -> ValueIterator[K]: ...
+    @overload
+    def __iter__(self) -> Iterator[K]: ...
+    @overload
+    def __iter__(self: MapKeysView[K]) -> Iterator[K]: ...
 
 class MapItemsView(Generic[K, V]):
     def __len__(self) -> int: ...

third-party/thrift/src/thrift/lib/python/test/mutable_map_test.py

@@ -19,7 +19,7 @@
 import string
 import unittest
 
-from typing import cast, Optional
+from typing import cast, KeysView, Optional
 
 from thrift.python.mutable_containers import (
     MapItemsView,
@@ -126,6 +126,19 @@ def test_type_hints(self) -> None:
             # to silence F841: not used variable
             _ = (v6, v7, v8, v9, v10)
 
+            ###################################################################
+
+            ### keys() ####
+
+            v11: MapKeysView[str] = mutable_map.keys()
+            v12: KeysView[str] = mutable_map.keys()
+
+            # pyre-ignore[9]: v13 is type `MapKeysView[int]` but is used as type `MapKeysView[str]`
+            v13: MapKeysView[int] = mutable_map.keys()
+
+            # to silence F841: not used variable
+            _ = (v11, v12, v13)
+
         except Exception:
             pass