Minor typing fixes (#12034)

These started failing in
https://github.com/matrix-org/synapse/pull/12031... I'm a bit mystified by how
they ever worked.

changelog.d/12034.misc

@@ -0,0 +1 @@
+Minor typing fixes.

synapse/federation/sender/per_destination_queue.py

@@ -381,7 +381,9 @@ class PerDestinationQueue:
                 )
             )
 
-        if self._last_successful_stream_ordering is None:
+        last_successful_stream_ordering = self._last_successful_stream_ordering
+
+        if last_successful_stream_ordering is None:
             # if it's still None, then this means we don't have the information
             # in our database ­ we haven't successfully sent a PDU to this server
             # (at least since the introduction of the feature tracking
@@ -394,8 +396,7 @@ class PerDestinationQueue:
         # get at most 50 catchup room/PDUs
         while True:
             event_ids = await self._store.get_catch_up_room_event_ids(
-                self._destination,
-                self._last_successful_stream_ordering,
+                self._destination, last_successful_stream_ordering
             )
 
             if not event_ids:
@@ -403,7 +404,7 @@ class PerDestinationQueue:
                 # of a race condition, so we check that no new events have been
                 # skipped due to us being in catch-up mode
 
-                if self._catchup_last_skipped > self._last_successful_stream_ordering:
+                if self._catchup_last_skipped > last_successful_stream_ordering:
                     # another event has been skipped because we were in catch-up mode
                     continue
 
@@ -470,7 +471,7 @@ class PerDestinationQueue:
                         # offline
                         if (
                             p.internal_metadata.stream_ordering
-                            < self._last_successful_stream_ordering
+                            < last_successful_stream_ordering
                         ):
                             continue
 
@@ -513,12 +514,11 @@ class PerDestinationQueue:
                 # from the *original* PDU, rather than the PDU(s) we actually
                 # send. This is because we use it to mark our position in the
                 # queue of missed PDUs to process.
-                self._last_successful_stream_ordering = (
-                    pdu.internal_metadata.stream_ordering
-                )
+                last_successful_stream_ordering = pdu.internal_metadata.stream_ordering
 
+                self._last_successful_stream_ordering = last_successful_stream_ordering
                 await self._store.set_destination_last_successful_stream_ordering(
-                    self._destination, self._last_successful_stream_ordering
+                    self._destination, last_successful_stream_ordering
                 )
 
     def _get_rr_edus(self, force_flush: bool) -> Iterable[Edu]:

synapse/handlers/message.py

@@ -550,10 +550,11 @@ class EventCreationHandler:
 
         if event_dict["type"] == EventTypes.Create and event_dict["state_key"] == "":
             room_version_id = event_dict["content"]["room_version"]
-            room_version_obj = KNOWN_ROOM_VERSIONS.get(room_version_id)
-            if not room_version_obj:
+            maybe_room_version_obj = KNOWN_ROOM_VERSIONS.get(room_version_id)
+            if not maybe_room_version_obj:
                 # this can happen if support is withdrawn for a room version
                 raise UnsupportedRoomVersionError(room_version_id)
+            room_version_obj = maybe_room_version_obj
         else:
             try:
                 room_version_obj = await self.store.get_room_version(
@@ -1145,12 +1146,13 @@ class EventCreationHandler:
             room_version_id = event.content.get(
                 "room_version", RoomVersions.V1.identifier
             )
-            room_version_obj = KNOWN_ROOM_VERSIONS.get(room_version_id)
-            if not room_version_obj:
+            maybe_room_version_obj = KNOWN_ROOM_VERSIONS.get(room_version_id)
+            if not maybe_room_version_obj:
                 raise UnsupportedRoomVersionError(
                     "Attempt to create a room with unsupported room version %s"
                     % (room_version_id,)
                 )
+            room_version_obj = maybe_room_version_obj
         else:
             room_version_obj = await self.store.get_room_version(event.room_id)
 

synapse/handlers/register.py

@@ -320,12 +320,12 @@ class RegistrationHandler:
                 if fail_count > 10:
                     raise SynapseError(500, "Unable to find a suitable guest user ID")
 
-                localpart = await self.store.generate_user_id()
-                user = UserID(localpart, self.hs.hostname)
+                generated_localpart = await self.store.generate_user_id()
+                user = UserID(generated_localpart, self.hs.hostname)
                 user_id = user.to_string()
                 self.check_user_id_not_appservice_exclusive(user_id)
                 if generate_display_name:
-                    default_display_name = localpart
+                    default_display_name = generated_localpart
                 try:
                     await self.register_with_store(
                         user_id=user_id,