Restore error back

Author: sterliakov

test-data/unit/check-typeguard.test

@@ -829,6 +829,7 @@ def process_model(model: Union[MODEL_A, MODEL_B]) -> int:
 
 def handle(model: Model) -> int:
     if is_model_a(model) or is_model_b(model):
-        return process_model(model)
+        # TODO: should start passing after #18896
+        return process_model(model)  # E: Argument 1 to "process_model" has incompatible type "Model"; expected "Union[Literal[Model.MODEL_A1, Model.MODEL_A2], Literal[Model.MODEL_B]]"
     return 0
 [builtins fixtures/tuple.pyi]