update generic type params

Author: eternal-sorrow

i3ipc/aio/connection.py

@@ -36,10 +36,12 @@ def ensure_future(obj):
 _BaseEvent = TypeVar('_BaseEvent', bound=IpcBaseEvent, contravariant=True)
 
 
-Handler: TypeAlias = Union[
-    Callable[['Connection', _BaseEvent], None], Callable[['Connection', _BaseEvent], Coroutine]
+_Handler: TypeAlias = Union[
+    Callable[['Connection', _BaseEvent], None], Callable[['Connection', _BaseEvent], Coroutine[None, None, None]]
 ]
 
+Handler: TypeAlias = _Handler[IpcBaseEvent]
+
 
 class _Subscription(TypedDict):
     event: str
@@ -530,8 +532,8 @@ async def subscribe(self, events: Union[list[Event], list[str]], force: bool = F
 
         await self._loop.sock_sendall(self._sub_socket, _pack(MessageType.SUBSCRIBE, payload))
 
-    def on(self, event: Union[Event, str], handler: Optional[Handler] = None):
-        def on_wrapped(handler):
+    def on(self, event: Union[Event, str], handler: Optional[Handler] = None) ->Handler|Callable[[Handler], Handler]:
+        def on_wrapped(handler: Handler) -> Handler:
             self._on(event, handler)
             return handler