♻️ improve dependent structure (#1227)

nonebot/dependencies/__init__.py

@@ -6,15 +6,19 @@ FrontMatter:
 """
 
 import abc
+import asyncio
 import inspect
+from dataclasses import field, dataclass
 from typing import (
     Any,
     Dict,
     List,
     Type,
+    Tuple,
     Generic,
     TypeVar,
     Callable,
+    Iterable,
     Optional,
     Awaitable,
     cast,
@@ -25,7 +29,6 @@ from pydantic.schema import get_annotation_from_field_info
 from pydantic.fields import Required, FieldInfo, Undefined, ModelField
 
 from nonebot.log import logger
-from nonebot.exception import TypeMisMatch
 from nonebot.typing import _DependentCallable
 from nonebot.utils import run_sync, is_coroutine_callable
 
@@ -43,25 +46,29 @@ class Param(abc.ABC, FieldInfo):
 
     @classmethod
     def _check_param(
-        cls, dependent: "Dependent", name: str, param: inspect.Parameter
+        cls, param: inspect.Parameter, allow_types: Tuple[Type["Param"], ...]
     ) -> Optional["Param"]:
-        return None
+        return
 
     @classmethod
     def _check_parameterless(
-        cls, dependent: "Dependent", value: Any
+        cls, value: Any, allow_types: Tuple[Type["Param"], ...]
     ) -> Optional["Param"]:
-        return None
+        return
 
     @abc.abstractmethod
     async def _solve(self, **kwargs: Any) -> Any:
         raise NotImplementedError
 
+    async def _check(self, **kwargs: Any) -> None:
+        return
+
 
 class CustomConfig(BaseConfig):
     arbitrary_types_allowed = True
 
 
+@dataclass(frozen=True)
 class Dependent(Generic[R]):
     """依赖注入容器
 
@@ -73,76 +80,34 @@ class Dependent(Generic[R]):
         allow_types: 允许的参数类型
     """
 
-    def __init__(
-        self,
-        *,
-        call: _DependentCallable[R],
-        pre_checkers: Optional[List[Param]] = None,
-        params: Optional[List[ModelField]] = None,
-        parameterless: Optional[List[Param]] = None,
-        allow_types: Optional[List[Type[Param]]] = None,
-    ) -> None:
-        self.call = call
-        self.pre_checkers = pre_checkers or []
-        self.params = params or []
-        self.parameterless = parameterless or []
-        self.allow_types = allow_types or []
+    call: _DependentCallable[R]
+    params: Tuple[ModelField] = field(default_factory=tuple)
+    parameterless: Tuple[Param] = field(default_factory=tuple)
 
     def __repr__(self) -> str:
-        return (
-            f"<Dependent call={self.call}, params={self.params},"
-            f" parameterless={self.parameterless}>"
-        )
-
-    def __str__(self) -> str:
-        return self.__repr__()
+        return f"<Dependent call={self.call}>"
 
     async def __call__(self, **kwargs: Any) -> R:
+        # do pre-check
+        await self.check(**kwargs)
+
+        # solve param values
         values = await self.solve(**kwargs)
 
+        # call function
         if is_coroutine_callable(self.call):
             return await cast(Callable[..., Awaitable[R]], self.call)(**values)
         else:
             return await run_sync(cast(Callable[..., R], self.call))(**values)
 
-    def parse_param(self, name: str, param: inspect.Parameter) -> Param:
-        for allow_type in self.allow_types:
-            if field_info := allow_type._check_param(self, name, param):
-                return field_info
-        raise ValueError(
-            f"Unknown parameter {name} for function {self.call} with type {param.annotation}"
-        )
+    @staticmethod
+    def parse_params(
+        call: _DependentCallable[R], allow_types: Tuple[Type[Param], ...]
+    ) -> Tuple[ModelField]:
+        fields: List[ModelField] = []
+        params = get_typed_signature(call).parameters.values()
 
-    def parse_parameterless(self, value: Any) -> Param:
-        for allow_type in self.allow_types:
-            if field_info := allow_type._check_parameterless(self, value):
-                return field_info
-        raise ValueError(
-            f"Unknown parameterless {value} for function {self.call} with type {type(value)}"
-        )
-
-    def prepend_parameterless(self, value: Any) -> None:
-        self.parameterless.insert(0, self.parse_parameterless(value))
-
-    def append_parameterless(self, value: Any) -> None:
-        self.parameterless.append(self.parse_parameterless(value))
-
-    @classmethod
-    def parse(
-        cls,
-        *,
-        call: _DependentCallable[R],
-        parameterless: Optional[List[Any]] = None,
-        allow_types: Optional[List[Type[Param]]] = None,
-    ) -> "Dependent[R]":
-        signature = get_typed_signature(call)
-        params = signature.parameters
-        dependent = cls(
-            call=call,
-            allow_types=allow_types,
-        )
-
-        for param_name, param in params.items():
+        for param in params:
             default_value = Required
             if param.default != param.empty:
                 default_value = param.default
@@ -150,7 +115,13 @@ class Dependent(Generic[R]):
             if isinstance(default_value, Param):
                 field_info = default_value
             else:
-                field_info = dependent.parse_param(param_name, param)
+                for allow_type in allow_types:
+                    if field_info := allow_type._check_param(param, allow_types):
+                        break
+                else:
+                    raise ValueError(
+                        f"Unknown parameter {param.name} for function {call} with type {param.annotation}"
+                    )
 
             default_value = field_info.default
 
@@ -159,11 +130,12 @@ class Dependent(Generic[R]):
             if param.annotation != param.empty:
                 annotation = param.annotation
             annotation = get_annotation_from_field_info(
-                annotation, field_info, param_name
+                annotation, field_info, param.name
             )
-            dependent.params.append(
+
+            fields.append(
                 ModelField(
-                    name=param_name,
+                    name=param.name,
                     type_=annotation,
                     class_validators=None,
                     model_config=CustomConfig,
@@ -173,49 +145,69 @@ class Dependent(Generic[R]):
                 )
             )
 
-        parameterless_params = [
-            dependent.parse_parameterless(param) for param in (parameterless or [])
-        ]
-        dependent.parameterless.extend(parameterless_params)
+        return tuple(fields)
+
+    @staticmethod
+    def parse_parameterless(
+        parameterless: Tuple[Any, ...], allow_types: Tuple[Type[Param], ...]
+    ) -> Tuple[Param, ...]:
+        parameterless_params: List[Param] = []
+        for value in parameterless:
+            for allow_type in allow_types:
+                if param := allow_type._check_parameterless(value, allow_types):
+                    break
+            else:
+                raise ValueError(f"Unknown parameterless {value}")
+            parameterless_params.append(param)
+        return tuple(parameterless_params)
+
+    @classmethod
+    def parse(
+        cls,
+        *,
+        call: _DependentCallable[R],
+        parameterless: Optional[Iterable[Any]] = None,
+        allow_types: Iterable[Type[Param]],
+    ) -> "Dependent[R]":
+        allow_types = tuple(allow_types)
+
+        params = cls.parse_params(call, allow_types)
+        parameterless_params = (
+            tuple()
+            if parameterless is None
+            else cls.parse_parameterless(tuple(parameterless), allow_types)
+        )
 
         logger.trace(
             f"Parsed dependent with call={call}, "
-            f"params={[param.field_info for param in dependent.params]}, "
-            f"parameterless={dependent.parameterless}"
+            f"params={params}, "
+            f"parameterless={parameterless_params}"
         )
 
-        return dependent
+        return cls(call, params, parameterless_params)
 
-    async def solve(
-        self,
-        **params: Any,
-    ) -> Dict[str, Any]:
-        values: Dict[str, Any] = {}
+    async def check(self, **params: Any) -> None:
+        await asyncio.gather(*(param._check(**params) for param in self.parameterless))
+        await asyncio.gather(
+            *(cast(Param, param.field_info)._check(**params) for param in self.params)
+        )
 
-        for checker in self.pre_checkers:
-            await checker._solve(**params)
+    async def _solve_field(self, field: ModelField, params: Dict[str, Any]) -> Any:
+        value = await cast(Param, field.field_info)._solve(**params)
+        if value is Undefined:
+            value = field.get_default()
+        return check_field_type(field, value)
 
+    async def solve(self, **params: Any) -> Dict[str, Any]:
+        # solve parameterless
         for param in self.parameterless:
             await param._solve(**params)
 
-        for field in self.params:
-            field_info = field.field_info
-            assert isinstance(field_info, Param), "Params must be subclasses of Param"
-            value = await field_info._solve(**params)
-            if value is Undefined:
-                value = field.get_default()
-
-            try:
-                values[field.name] = check_field_type(field, value)
-            except TypeMisMatch:
-                logger.debug(
-                    f"{field_info} "
-                    f"type {type(value)} not match depends {self.call} "
-                    f"annotation {field._type_display()}, ignored"
-                )
-                raise
-
-        return values
+        # solve param values
+        values = await asyncio.gather(
+            *(self._solve_field(field, params) for field in self.params)
+        )
+        return {field.name: value for field, value in zip(self.params, values)}
 
 
 __autodoc__ = {"CustomConfig": False}

nonebot/internal/matcher.py

@@ -12,6 +12,7 @@ from typing import (
     Union,
     TypeVar,
     Callable,
+    Iterable,
     NoReturn,
     Optional,
     overload,
@@ -133,7 +134,7 @@ class Matcher(metaclass=MatcherMeta):
     _default_permission_updater: Optional[Dependent[Permission]] = None
     """事件响应器权限更新函数"""
 
-    HANDLER_PARAM_TYPES = [
+    HANDLER_PARAM_TYPES = (
         DependParam,
         BotParam,
         EventParam,
@@ -141,7 +142,7 @@ class Matcher(metaclass=MatcherMeta):
         ArgParam,
         MatcherParam,
         DefaultParam,
-    ]
+    )
 
     def __init__(self):
         self.handlers = self.handlers.copy()
@@ -153,9 +154,6 @@ class Matcher(metaclass=MatcherMeta):
             f"priority={self.priority}, temp={self.temp}>"
         )
 
-    def __str__(self) -> str:
-        return repr(self)
-
     @classmethod
     def new(
         cls,
@@ -219,27 +217,35 @@ class Matcher(metaclass=MatcherMeta):
                 "temp": temp,
                 "expire_time": (
                     expire_time
-                    if isinstance(expire_time, datetime)
-                    else expire_time and datetime.now() + expire_time
+                    and (
+                        expire_time
+                        if isinstance(expire_time, datetime)
+                        else datetime.now() + expire_time
+                    )
                 ),
                 "priority": priority,
                 "block": block,
                 "_default_state": default_state or {},
                 "_default_type_updater": (
                     default_type_updater
-                    if isinstance(default_type_updater, Dependent)
-                    else default_type_updater
-                    and Dependent[str].parse(
-                        call=default_type_updater, allow_types=cls.HANDLER_PARAM_TYPES
+                    and (
+                        default_type_updater
+                        if isinstance(default_type_updater, Dependent)
+                        else Dependent[str].parse(
+                            call=default_type_updater,
+                            allow_types=cls.HANDLER_PARAM_TYPES,
+                        )
                     )
                 ),
                 "_default_permission_updater": (
                     default_permission_updater
-                    if isinstance(default_permission_updater, Dependent)
-                    else default_permission_updater
-                    and Dependent[Permission].parse(
-                        call=default_permission_updater,
-                        allow_types=cls.HANDLER_PARAM_TYPES,
+                    and (
+                        default_permission_updater
+                        if isinstance(default_permission_updater, Dependent)
+                        else Dependent[Permission].parse(
+                            call=default_permission_updater,
+                            allow_types=cls.HANDLER_PARAM_TYPES,
+                        )
                     )
                 ),
             },
@@ -327,7 +333,7 @@ class Matcher(metaclass=MatcherMeta):
 
     @classmethod
     def append_handler(
-        cls, handler: T_Handler, parameterless: Optional[List[Any]] = None
+        cls, handler: T_Handler, parameterless: Optional[Iterable[Any]] = None
     ) -> Dependent[Any]:
         handler_ = Dependent[Any].parse(
             call=handler,
@@ -339,7 +345,7 @@ class Matcher(metaclass=MatcherMeta):
 
     @classmethod
     def handle(
-        cls, parameterless: Optional[List[Any]] = None
+        cls, parameterless: Optional[Iterable[Any]] = None
     ) -> Callable[[T_Handler], T_Handler]:
         """装饰一个函数来向事件响应器直接添加一个处理函数
 
@@ -355,7 +361,7 @@ class Matcher(metaclass=MatcherMeta):
 
     @classmethod
     def receive(
-        cls, id: str = "", parameterless: Optional[List[Any]] = None
+        cls, id: str = "", parameterless: Optional[Iterable[Any]] = None
     ) -> Callable[[T_Handler], T_Handler]:
         """装饰一个函数来指示 NoneBot 在接收用户新的一条消息后继续运行该函数
 
@@ -373,14 +379,21 @@ class Matcher(metaclass=MatcherMeta):
                 return
             await matcher.reject()
 
-        _parameterless = [Depends(_receive), *(parameterless or [])]
+        _parameterless = (Depends(_receive), *(parameterless or tuple()))
 
         def _decorator(func: T_Handler) -> T_Handler:
 
             if cls.handlers and cls.handlers[-1].call is func:
                 func_handler = cls.handlers[-1]
-                for depend in reversed(_parameterless):
-                    func_handler.prepend_parameterless(depend)
+                new_handler = Dependent(
+                    call=func_handler.call,
+                    params=func_handler.params,
+                    parameterless=Dependent.parse_parameterless(
+                        tuple(_parameterless), cls.HANDLER_PARAM_TYPES
+                    )
+                    + func_handler.parameterless,
+                )
+                cls.handlers[-1] = new_handler
             else:
                 cls.append_handler(func, parameterless=_parameterless)
 
@@ -393,7 +406,7 @@ class Matcher(metaclass=MatcherMeta):
         cls,
         key: str,
         prompt: Optional[Union[str, Message, MessageSegment, MessageTemplate]] = None,
-        parameterless: Optional[List[Any]] = None,
+        parameterless: Optional[Iterable[Any]] = None,
     ) -> Callable[[T_Handler], T_Handler]:
         """装饰一个函数来指示 NoneBot 获取一个参数 `key`
 
@@ -414,17 +427,21 @@ class Matcher(metaclass=MatcherMeta):
                 return
             await matcher.reject(prompt)
 
-        _parameterless = [
-            Depends(_key_getter),
-            *(parameterless or []),
-        ]
+        _parameterless = (Depends(_key_getter), *(parameterless or tuple()))
 
         def _decorator(func: T_Handler) -> T_Handler:
 
             if cls.handlers and cls.handlers[-1].call is func:
                 func_handler = cls.handlers[-1]
-                for depend in reversed(_parameterless):
-                    func_handler.prepend_parameterless(depend)
+                new_handler = Dependent(
+                    call=func_handler.call,
+                    params=func_handler.params,
+                    parameterless=Dependent.parse_parameterless(
+                        tuple(_parameterless), cls.HANDLER_PARAM_TYPES
+                    )
+                    + func_handler.parameterless,
+                )
+                cls.handlers[-1] = new_handler
             else:
                 cls.append_handler(func, parameterless=_parameterless)
 

nonebot/internal/params.py

@@ -1,8 +1,7 @@
 import asyncio
 import inspect
-import warnings
-from typing import TYPE_CHECKING, Any, Literal, Callable, Optional, cast
 from contextlib import AsyncExitStack, contextmanager, asynccontextmanager
+from typing import TYPE_CHECKING, Any, Type, Tuple, Literal, Callable, Optional, cast
 
 from pydantic.fields import Required, Undefined, ModelField
 
@@ -76,10 +75,7 @@ class DependParam(Param):
 
     @classmethod
     def _check_param(
-        cls,
-        dependent: Dependent,
-        name: str,
-        param: inspect.Parameter,
+        cls, param: inspect.Parameter, allow_types: Tuple[Type[Param], ...]
     ) -> Optional["DependParam"]:
         if isinstance(param.default, DependsInner):
             dependency: T_Handler
@@ -90,22 +86,20 @@ class DependParam(Param):
                 dependency = param.default.dependency
             sub_dependent = Dependent[Any].parse(
                 call=dependency,
-                allow_types=dependent.allow_types,
+                allow_types=allow_types,
             )
-            dependent.pre_checkers.extend(sub_dependent.pre_checkers)
-            sub_dependent.pre_checkers.clear()
             return cls(
                 Required, use_cache=param.default.use_cache, dependent=sub_dependent
             )
 
     @classmethod
     def _check_parameterless(
-        cls, dependent: "Dependent", value: Any
+        cls, value: Any, allow_types: Tuple[Type[Param], ...]
     ) -> Optional["Param"]:
         if isinstance(value, DependsInner):
             assert value.dependency, "Dependency cannot be empty"
             dependent = Dependent[Any].parse(
-                call=value.dependency, allow_types=dependent.allow_types
+                call=value.dependency, allow_types=allow_types
             )
             return cls(Required, use_cache=value.use_cache, dependent=dependent)
 
@@ -119,8 +113,7 @@ class DependParam(Param):
         dependency_cache = {} if dependency_cache is None else dependency_cache
 
         sub_dependent: Dependent = self.extra["dependent"]
-        sub_dependent.call = cast(Callable[..., Any], sub_dependent.call)
-        call = sub_dependent.call
+        call = cast(Callable[..., Any], sub_dependent.call)
 
         # solve sub dependency with current cache
         sub_values = await sub_dependent.solve(
@@ -132,7 +125,7 @@ class DependParam(Param):
         # run dependency function
         task: asyncio.Task[Any]
         if use_cache and call in dependency_cache:
-            solved = await dependency_cache[call]
+            return await dependency_cache[call]
         elif is_gen_callable(call) or is_async_gen_callable(call):
             assert isinstance(
                 stack, AsyncExitStack
@@ -143,30 +136,20 @@ class DependParam(Param):
                 cm = asynccontextmanager(call)(**sub_values)
             task = asyncio.create_task(stack.enter_async_context(cm))
             dependency_cache[call] = task
-            solved = await task
+            return await task
         elif is_coroutine_callable(call):
             task = asyncio.create_task(call(**sub_values))
             dependency_cache[call] = task
-            solved = await task
+            return await task
         else:
             task = asyncio.create_task(run_sync(call)(**sub_values))
             dependency_cache[call] = task
-            solved = await task
+            return await task
 
-        return solved
-
-
-class _BotChecker(Param):
-    async def _solve(self, bot: "Bot", **kwargs: Any) -> Any:
-        field: ModelField = self.extra["field"]
-        try:
-            return check_field_type(field, bot)
-        except TypeMisMatch:
-            logger.debug(
-                f"Bot type {type(bot)} not match "
-                f"annotation {field._type_display()}, ignored"
-            )
-            raise
+    async def _check(self, **kwargs: Any) -> None:
+        # run sub dependent pre-checkers
+        sub_dependent: Dependent = self.extra["dependent"]
+        await sub_dependent.check(**kwargs)
 
 
 class BotParam(Param):
@@ -174,45 +157,32 @@ class BotParam(Param):
 
     @classmethod
     def _check_param(
-        cls, dependent: Dependent, name: str, param: inspect.Parameter
+        cls, param: inspect.Parameter, allow_types: Tuple[Type[Param], ...]
     ) -> Optional["BotParam"]:
         from nonebot.adapters import Bot
 
         if param.default == param.empty:
             if generic_check_issubclass(param.annotation, Bot):
+                checker: Optional[ModelField] = None
                 if param.annotation is not Bot:
-                    dependent.pre_checkers.append(
-                        _BotChecker(
-                            Required,
-                            field=ModelField(
-                                name=name,
-                                type_=param.annotation,
-                                class_validators=None,
-                                model_config=CustomConfig,
-                                default=None,
-                                required=True,
-                            ),
-                        )
+                    checker = ModelField(
+                        name=param.name,
+                        type_=param.annotation,
+                        class_validators=None,
+                        model_config=CustomConfig,
+                        default=None,
+                        required=True,
                     )
-                return cls(Required)
-            elif param.annotation == param.empty and name == "bot":
+                return cls(Required, checker=checker)
+            elif param.annotation == param.empty and param.name == "bot":
                 return cls(Required)
 
     async def _solve(self, bot: "Bot", **kwargs: Any) -> Any:
         return bot
 
-
-class _EventChecker(Param):
-    async def _solve(self, event: "Event", **kwargs: Any) -> Any:
-        field: ModelField = self.extra["field"]
-        try:
-            return check_field_type(field, event)
-        except TypeMisMatch:
-            logger.debug(
-                f"Event type {type(event)} not match "
-                f"annotation {field._type_display()}, ignored"
-            )
-            raise
+    async def _check(self, bot: "Bot", **kwargs: Any) -> None:
+        if checker := self.extra.get("checker", None):
+            check_field_type(checker, bot)
 
 
 class EventParam(Param):
@@ -220,33 +190,33 @@ class EventParam(Param):
 
     @classmethod
     def _check_param(
-        cls, dependent: Dependent, name: str, param: inspect.Parameter
+        cls, param: inspect.Parameter, allow_types: Tuple[Type[Param], ...]
     ) -> Optional["EventParam"]:
         from nonebot.adapters import Event
 
         if param.default == param.empty:
             if generic_check_issubclass(param.annotation, Event):
+                checker: Optional[ModelField] = None
                 if param.annotation is not Event:
-                    dependent.pre_checkers.append(
-                        _EventChecker(
-                            Required,
-                            field=ModelField(
-                                name=name,
-                                type_=param.annotation,
-                                class_validators=None,
-                                model_config=CustomConfig,
-                                default=None,
-                                required=True,
-                            ),
-                        )
+                    checker = ModelField(
+                        name=param.name,
+                        type_=param.annotation,
+                        class_validators=None,
+                        model_config=CustomConfig,
+                        default=None,
+                        required=True,
                     )
-                return cls(Required)
-            elif param.annotation == param.empty and name == "event":
+                return cls(Required, checker=checker)
+            elif param.annotation == param.empty and param.name == "event":
                 return cls(Required)
 
     async def _solve(self, event: "Event", **kwargs: Any) -> Any:
         return event
 
+    async def _check(self, event: "Event", **kwargs: Any) -> Any:
+        if checker := self.extra.get("checker", None):
+            check_field_type(checker, event)
+
 
 class StateInner(T_State):
     ...
@@ -257,14 +227,14 @@ class StateParam(Param):
 
     @classmethod
     def _check_param(
-        cls, dependent: Dependent, name: str, param: inspect.Parameter
+        cls, param: inspect.Parameter, allow_types: Tuple[Type[Param], ...]
     ) -> Optional["StateParam"]:
         if isinstance(param.default, StateInner):
             return cls(Required)
         elif param.default == param.empty:
             if param.annotation is T_State:
                 return cls(Required)
-            elif param.annotation == param.empty and name == "state":
+            elif param.annotation == param.empty and param.name == "state":
                 return cls(Required)
 
     async def _solve(self, state: T_State, **kwargs: Any) -> Any:
@@ -276,12 +246,12 @@ class MatcherParam(Param):
 
     @classmethod
     def _check_param(
-        cls, dependent: Dependent, name: str, param: inspect.Parameter
+        cls, param: inspect.Parameter, allow_types: Tuple[Type[Param], ...]
     ) -> Optional["MatcherParam"]:
         from nonebot.matcher import Matcher
 
         if generic_check_issubclass(param.annotation, Matcher) or (
-            param.annotation == param.empty and name == "matcher"
+            param.annotation == param.empty and param.name == "matcher"
         ):
             return cls(Required)
 
@@ -317,10 +287,12 @@ class ArgParam(Param):
 
     @classmethod
     def _check_param(
-        cls, dependent: Dependent, name: str, param: inspect.Parameter
+        cls, param: inspect.Parameter, allow_types: Tuple[Type[Param], ...]
     ) -> Optional["ArgParam"]:
         if isinstance(param.default, ArgInner):
-            return cls(Required, key=param.default.key or name, type=param.default.type)
+            return cls(
+                Required, key=param.default.key or param.name, type=param.default.type
+            )
 
     async def _solve(self, matcher: "Matcher", **kwargs: Any) -> Any:
         message = matcher.get_arg(self.extra["key"])
@@ -339,10 +311,10 @@ class ExceptionParam(Param):
 
     @classmethod
     def _check_param(
-        cls, dependent: Dependent, name: str, param: inspect.Parameter
+        cls, param: inspect.Parameter, allow_types: Tuple[Type[Param], ...]
     ) -> Optional["ExceptionParam"]:
         if generic_check_issubclass(param.annotation, Exception) or (
-            param.annotation == param.empty and name == "exception"
+            param.annotation == param.empty and param.name == "exception"
         ):
             return cls(Required)
 
@@ -355,7 +327,7 @@ class DefaultParam(Param):
 
     @classmethod
     def _check_param(
-        cls, dependent: Dependent, name: str, param: inspect.Parameter
+        cls, param: inspect.Parameter, allow_types: Tuple[Type[Param], ...]
     ) -> Optional["DefaultParam"]:
         if param.default != param.empty:
             return cls(param.default)