perf: Squash weird mutable variable

src/service/rooms/event_handler/fetch_state.rs

@@ -26,9 +26,6 @@ impl super::Service {
 	/// to requesting the full state in PDU format from the remote (`GET
 	/// /_matrix/federation/v1/state, very slow in large rooms), and persists
 	/// them directly.
-	///
-	/// The end result is a result containing a map of shortstatekeys to event
-	/// IDs. The underlying `Option` is always `Some`.
 	#[tracing::instrument(skip_all)]
 	pub(super) async fn fetch_state(
 		&self,
@@ -36,7 +33,7 @@ impl super::Service {
 		create_event: &PduEvent,
 		room_id: &RoomId,
 		event_id: &EventId,
-	) -> Result<Option<HashMap<u64, OwnedEventId>>> {
+	) -> Result<HashMap<u64, OwnedEventId>> {
 		let start = Instant::now();
 		trace!(%origin, "Asking remote for state_ids");
 		let res: get_room_state_ids::v1::Response = match self
@@ -209,7 +206,7 @@ impl super::Service {
 			}
 		}
 		if state_events.is_empty() {
-			return Ok(Some(HashMap::new()));
+			return Ok(HashMap::new());
 		}
 
 		let mut state: HashMap<ShortStateKey, OwnedEventId> =
@@ -242,7 +239,7 @@ impl super::Service {
 			}
 		}
 		trace!(elapsed=?start.elapsed(), "fetch_state finished");
-		Ok(Some(state))
+		Ok(state)
 	}
 
 	async fn fetch_state_ids_from_backfill_servers(

src/service/rooms/event_handler/upgrade_outlier_pdu.rs

@@ -73,25 +73,24 @@ impl super::Service {
 			event_id = %incoming_pdu.event_id,
 			"Resolving state at event"
 		);
-		let mut state_at_incoming_event = if incoming_pdu.prev_events().count() == 1 {
+		let state_at_incoming_event = if incoming_pdu.prev_events().count() == 1 {
 			self.state_at_incoming_degree_one(&incoming_pdu).await?
 		} else {
 			self.state_at_incoming_resolved(&incoming_pdu, room_id, &room_version_rules)
 				.await?
 		};
+		let state_at_incoming_event = match state_at_incoming_event {
+			| Some(s) => s,
+			| None => {
+				trace!("Could not calculate incoming state, asking remote {origin} for it");
+				self.fetch_state(origin, create_event, room_id, incoming_pdu.event_id())
+					.await
+					.debug_inspect_err(|e| {
+						debug_error!("Could not fetch state from {origin}: {e}");
+					})?
+			},
+		};
 
-		if state_at_incoming_event.is_none() {
-			trace!("Could not calculate incoming state, asking remote {origin} for it");
-			state_at_incoming_event = self
-				.fetch_state(origin, create_event, room_id, incoming_pdu.event_id())
-				.await
-				.debug_inspect_err(|e| {
-					debug_error!("Could not fetch state from {origin}: {e}");
-				})?;
-		}
-
-		let state_at_incoming_event =
-			state_at_incoming_event.expect("we always set this to some above");
 		if state_at_incoming_event.is_empty()
 			&& *incoming_pdu.event_type() != StateEventType::RoomCreate.into()
 		{