SQ: Fix test on Python 3.14+

Author: davidfstr

tests.py

@@ -2122,30 +2122,60 @@ class MaybePoint1D(mypy_extensions.TypedDict, total=False):  # type: ignore[repo
 
         class TaggedMaybePoint1D(MaybePoint1D):
             name: str
-
-        self.assertTryCastSuccess(Point2D, {"x": 1, "y": 2}, strict=False)
-        self.assertTryCastFailure(Point2D, {"x": 1, "y": "string"}, strict=False)
-        self.assertTryCastFailure(Point2D, {"x": 1}, strict=False)
-
-        self.assertTryCastSuccess(Point3D, {"x": 1, "y": 2, "z": 3}, strict=False)
-        self.assertTryCastFailure(
-            Point3D, {"x": 1, "y": 2, "z": "string"}, strict=False
-        )
-        self.assertTryCastSuccess(Point3D, {"x": 1, "y": 2}, strict=False)
-        self.assertTryCastSuccess(Point3D, {"x": 1}, strict=False)  # surprise!
-        self.assertTryCastSuccess(Point3D, {"q": 1}, strict=False)  # surprise!
-
-        self.assertTryCastSuccess(MaybePoint1D, {"x": 1}, strict=False)
-        self.assertTryCastFailure(MaybePoint1D, {"x": "string"}, strict=False)
-        self.assertTryCastSuccess(MaybePoint1D, {}, strict=False)
-        self.assertTryCastSuccess(MaybePoint1D, {"q": 1}, strict=False)  # surprise!
-
-        self.assertTryCastSuccess(
-            TaggedMaybePoint1D, {"x": 1, "name": "one"}, strict=False
-        )
-        self.assertTryCastFailure(
-            TaggedMaybePoint1D, {"name": "one"}, strict=False
-        )  # surprise!
+        
+        @contextmanager
+        def assert_raises_if_python_3_14_or_later() -> Iterator[None]:
+            try:
+                yield
+            except TypeNotSupportedError as e:
+                if 'cannot determine which keys exist on a mypy_extensions.TypedDict' in str(e):
+                    if sys.version_info[:2] >= (3, 14):
+                        pass  # expected
+                    else:
+                        raise
+                else:
+                    raise
+            else:
+                if sys.version_info[:2] >= (3, 14):
+                    raise AssertionError('Expected TypeNotSupportedError to be raised')
+
+        with assert_raises_if_python_3_14_or_later():
+            self.assertTryCastSuccess(Point2D, {"x": 1, "y": 2}, strict=False)
+        with assert_raises_if_python_3_14_or_later():
+            self.assertTryCastFailure(Point2D, {"x": 1, "y": "string"}, strict=False)
+        with assert_raises_if_python_3_14_or_later():
+            self.assertTryCastFailure(Point2D, {"x": 1}, strict=False)
+
+        with assert_raises_if_python_3_14_or_later():
+            self.assertTryCastSuccess(Point3D, {"x": 1, "y": 2, "z": 3}, strict=False)
+        with assert_raises_if_python_3_14_or_later():
+            self.assertTryCastFailure(
+                Point3D, {"x": 1, "y": 2, "z": "string"}, strict=False
+            )
+        with assert_raises_if_python_3_14_or_later():
+            self.assertTryCastSuccess(Point3D, {"x": 1, "y": 2}, strict=False)
+        with assert_raises_if_python_3_14_or_later():
+            self.assertTryCastSuccess(Point3D, {"x": 1}, strict=False)  # surprise!
+        with assert_raises_if_python_3_14_or_later():
+            self.assertTryCastSuccess(Point3D, {"q": 1}, strict=False)  # surprise!
+
+        with assert_raises_if_python_3_14_or_later():
+            self.assertTryCastSuccess(MaybePoint1D, {"x": 1}, strict=False)
+        with assert_raises_if_python_3_14_or_later():
+            self.assertTryCastFailure(MaybePoint1D, {"x": "string"}, strict=False)
+        with assert_raises_if_python_3_14_or_later():
+            self.assertTryCastSuccess(MaybePoint1D, {}, strict=False)
+        with assert_raises_if_python_3_14_or_later():
+            self.assertTryCastSuccess(MaybePoint1D, {"q": 1}, strict=False)  # surprise!
+
+        with assert_raises_if_python_3_14_or_later():
+            self.assertTryCastSuccess(
+                TaggedMaybePoint1D, {"x": 1, "name": "one"}, strict=False
+            )
+        with assert_raises_if_python_3_14_or_later():
+            self.assertTryCastFailure(
+                TaggedMaybePoint1D, {"name": "one"}, strict=False
+            )  # surprise!
 
     # NOTE: Cannot combine the following two if-checks with an `and`
     #       because that is too complicated for Pyre to understand.

trycast/__init__.py

@@ -147,7 +147,7 @@ def __class_getitem__(cls, key):
 
     _typed_dict_meta_list.append(_MypyExtensionsTypedDictMeta)  # type: ignore[16]  # pyre
 except ImportError:
-    pass
+    _MypyExtensionsTypedDictMeta = None
 
 _typed_dict_metas = tuple(_typed_dict_meta_list)
 
@@ -156,6 +156,13 @@ def _is_typed_dict(tp: object) -> bool:
     return isinstance(tp, _typed_dict_metas)
 
 
+def _is_mypy_extensions_typed_dict(tp: object) -> bool:
+    return (
+        _MypyExtensionsTypedDictMeta is not None and
+        isinstance(tp, _MypyExtensionsTypedDictMeta)
+    )
+
+
 # _is_newtype
 if NewType.__class__.__name__ == "function":  # type: ignore[reportGeneralTypeIssues]  # pyright
     # Python 3.8 - 3.9
@@ -858,6 +865,16 @@ def _checkcast_typeddict(
         )  # resolve ForwardRefs in typed_dict_class.__annotations__
     else:
         resolved_annotations = typed_dict_class.__annotations__  # type: ignore[attr-defined]  # mypy
+    if (resolved_annotations == {} and 
+            _is_mypy_extensions_typed_dict(typed_dict_class) and
+            sys.version_info[:2] >= (3, 14)):
+        # NOTE: This is probably a bug in mypy_extensions.TypedDict or Python 3.14+.
+        #       But it is unlikely to be fixed because mypy_extensions.TypedDict is
+        #       deprecated.
+        raise TypeNotSupportedError(
+            f"{options.funcname} cannot determine which keys exist on a "
+            f"mypy_extensions.TypedDict in Python 3.14+"
+        )
 
     try:
         # {typing in Python 3.9+, typing_extensions}.TypedDict