Fix newly found linter issues (#3099)

Fixes the issues found in
https://github.com/matrix-org/dendrite/actions/runs/5155539352/jobs/9285342056#step:5:22.
Only naked returns in longer functions.

syncapi/routing/messages.go

@@ -314,11 +314,12 @@ func (r *messagesReq) retrieveEvents() (
 	clientEvents []synctypes.ClientEvent, start,
 	end types.TopologyToken, err error,
 ) {
+	emptyToken := types.TopologyToken{}
 	// Retrieve the events from the local database.
 	streamEvents, err := r.snapshot.GetEventsInTopologicalRange(r.ctx, r.from, r.to, r.roomID, r.filter, r.backwardOrdering)
 	if err != nil {
 		err = fmt.Errorf("GetEventsInRange: %w", err)
-		return
+		return []synctypes.ClientEvent{}, emptyToken, emptyToken, err
 	}
 
 	var events []*rstypes.HeaderedEvent
@@ -333,11 +334,11 @@ func (r *messagesReq) retrieveEvents() (
 	// on the ordering), or we've reached a backward extremity.
 	if len(streamEvents) == 0 {
 		if events, err = r.handleEmptyEventsSlice(); err != nil {
-			return
+			return []synctypes.ClientEvent{}, emptyToken, emptyToken, err
 		}
 	} else {
 		if events, err = r.handleNonEmptyEventsSlice(streamEvents); err != nil {
-			return
+			return []synctypes.ClientEvent{}, emptyToken, emptyToken, err
 		}
 	}
 

syncapi/streams/stream_pdu.go

@@ -489,7 +489,7 @@ func (p *PDUStreamProvider) getJoinResponseForCompleteSync(
 
 	stateEvents, err := snapshot.CurrentState(ctx, roomID, stateFilter, excludingEventIDs)
 	if err != nil {
-		return
+		return jr, err
 	}
 
 	jr.Summary, err = snapshot.GetRoomSummary(ctx, roomID, device.UserID)
@@ -542,7 +542,7 @@ func (p *PDUStreamProvider) getJoinResponseForCompleteSync(
 		}
 		backwardTopologyPos, backwardStreamPos, err = snapshot.PositionInTopology(ctx, event.EventID())
 		if err != nil {
-			return
+			return jr, err
 		}
 		prevBatch = &types.TopologyToken{
 			Depth:       backwardTopologyPos,