Update src/frequenz/channels/_receiver.py

Co-authored-by: Sahas Subramanian <[email protected]>
Signed-off-by: Leandro Lucarella <[email protected]>

src/frequenz/channels/_receiver.py

@@ -316,15 +316,14 @@ def filter(
         """
         ...  # pylint: disable=unnecessary-ellipsis
 
-    # We need to use Any here because otherwise _Filter would have to deal with two
-    # different signatures. We can create two filter classes, one for regular functions
-    # and one for type guards, but then there is no way to tell at runtime which
-    # function is a type guard and which isn't to instantiate the correct class.
-    # Using Any here has no impact though, as thanks to the overloads, only the
-    # overloaded types will be accepted.
     def filter(
-        self, filter_function: Callable[[ReceiverMessageT_co], Any], /
-    ) -> Receiver[Any]:
+        self,
+        filter_function: (
+            Callable[[ReceiverMessageT_co], bool]
+            | Callable[[ReceiverMessageT_co], TypeGuard[FilteredMessageT_co]]
+        ),
+        /,
+    ) -> Receiver[ReceiverMessageT_co] | Receiver[FilteredMessageT_co]:
         """Apply a filter function on the messages on a receiver.
 
         Note: