{"id":"cf83c0b4cd8c4c48","repo":"pydantic/pydantic","slug":"expected-a-class-got-type-param-r","errorCode":null,"errorMessage":"Expected a class, got {type_param!r}","messagePattern":"Expected a class, got (.+?)","errorType":"exception","errorClass":"TypeError","httpStatus":null,"severity":"error","filePath":"pydantic/_internal/_generate_schema.py","lineNumber":1757,"sourceCode":"            else:\n                return self._type_schema()\n        elif is_union_origin(get_origin(type_param)):\n            return self._union_is_subclass_schema(type_param)\n        else:\n            if typing_objects.is_self(type_param):\n                type_param = self._resolve_self_type(type_param)\n            if _typing_extra.is_generic_alias(type_param):\n                raise PydanticUserError(\n                    'Subscripting `type[]` with an already parametrized type is not supported. '\n                    f'Instead of using type[{type_param!r}], use type[{_repr.display_as_type(get_origin(type_param))}].',\n                    code=None,\n                )\n            if not inspect.isclass(type_param):\n                # when using type[None], this doesn't type convert to type[NoneType], and None isn't a class\n                # so we handle it manually here\n                if type_param is None:\n                    return core_schema.is_subclass_schema(NoneType)\n                raise TypeError(f'Expected a class, got {type_param!r}')\n            return core_schema.is_subclass_schema(type_param)\n\n    def _sequence_schema(self, items_type: Any) -> core_schema.CoreSchema:\n        \"\"\"Generate schema for a Sequence, e.g. `Sequence[int]`.\"\"\"\n        from ._serializers import serialize_sequence_via_list\n\n        item_type_schema = self.generate_schema(items_type)\n        list_schema = core_schema.list_schema(item_type_schema)\n\n        json_schema = smart_deepcopy(list_schema)\n        python_schema = core_schema.is_instance_schema(typing.Sequence, cls_repr='Sequence')\n        if not typing_objects.is_any(items_type):\n            from ._validators import sequence_validator\n\n            python_schema = core_schema.chain_schema(\n                [python_schema, core_schema.no_info_wrap_validator_function(sequence_validator, list_schema)],\n            )\n","sourceCodeStart":1739,"sourceCodeEnd":1775,"githubUrl":"https://github.com/pydantic/pydantic/blob/2e5f0e2b4218de31709f1cf9c5bc61ea97a68835/pydantic/_internal/_generate_schema.py#L1739-L1775","documentation":"Error \"Expected a class, got {type_param!r}\" thrown in pydantic/pydantic.","triggerScenarios":"Thrown at pydantic/_internal/_generate_schema.py:1757 when the library encounters an invalid state.","commonSituations":"See trigger scenarios.","solutions":[],"exampleFix":null,"handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"analyzedSha":"2e5f0e2b4218de31709f1cf9c5bc61ea97a68835","analyzedAt":"2026-08-04T19:54:21.281Z","schemaVersion":2}