enable let_underscore_must_use lint

src/api/client_server/membership.rs

@@ -1400,7 +1400,9 @@ pub(crate) async fn leave_all_rooms(user_id: &UserId) -> Result<()> {
             Err(_) => continue,
         };
 
-        let _ = leave_room(user_id, &room_id, None).await;
+        if let Err(error) = leave_room(user_id, &room_id, None).await {
+            warn!(%user_id, %room_id, %error, "failed to leave room");
+        }
     }
 
     Ok(())

src/api/client_server/profile.rs

@@ -13,6 +13,7 @@ use ruma::{
 };
 use serde_json::value::to_raw_value;
 use std::sync::Arc;
+use tracing::warn;
 
 /// # `PUT /_matrix/client/r0/profile/{userId}/displayname`
 ///
@@ -84,11 +85,14 @@ pub(crate) async fn set_displayname_route(
         );
         let state_lock = mutex_state.lock().await;
 
-        let _ = services()
+        if let Err(error) = services()
             .rooms
             .timeline
             .build_and_append_pdu(pdu_builder, sender_user, &room_id, &state_lock)
-            .await;
+            .await
+        {
+            warn!(%error, "failed to add PDU");
+        }
     }
 
     Ok(set_display_name::v3::Response {})
@@ -198,11 +202,14 @@ pub(crate) async fn set_avatar_url_route(
         );
         let state_lock = mutex_state.lock().await;
 
-        let _ = services()
+        if let Err(error) = services()
             .rooms
             .timeline
             .build_and_append_pdu(pdu_builder, sender_user, &room_id, &state_lock)
-            .await;
+            .await
+        {
+            warn!(%error, "failed to add PDU");
+        };
     }
 
     Ok(set_avatar_url::v3::Response {})

src/api/client_server/room.rs

@@ -480,7 +480,11 @@ pub(crate) async fn create_room_route(
     // 8. Events implied by invite (and TODO: invite_3pid)
     drop(state_lock);
     for user_id in &body.invite {
-        let _ = invite_helper(sender_user, user_id, &room_id, None, body.is_direct).await;
+        if let Err(error) =
+            invite_helper(sender_user, user_id, &room_id, None, body.is_direct).await
+        {
+            warn!(%error, "invite helper failed");
+        };
     }
 
     // Homeserver specific stuff

src/api/client_server/sync.rs

@@ -29,7 +29,7 @@ use std::{
     time::Duration,
 };
 use tokio::sync::watch::Sender;
-use tracing::{error, info};
+use tracing::{debug, error, info};
 
 /// # `GET /_matrix/client/r0/sync`
 ///
@@ -164,7 +164,8 @@ async fn sync_helper_wrapper(
         }
     }
 
-    let _ = tx.send(Some(r.map(|(r, _)| r)));
+    tx.send(Some(r.map(|(r, _)| r)))
+        .expect("receiver should not be dropped");
 }
 
 async fn sync_helper(
@@ -543,7 +544,10 @@ async fn sync_helper(
         if duration.as_secs() > 30 {
             duration = Duration::from_secs(30);
         }
-        let _ = tokio::time::timeout(duration, watcher).await;
+        match tokio::time::timeout(duration, watcher).await {
+            Ok(x) => x.expect("watcher should succeed"),
+            Err(error) => debug!(%error, "timed out"),
+        };
         Ok((response, false))
     } else {
         Ok((response, since != next_batch)) // Only cache if we made progress
@@ -1681,7 +1685,10 @@ pub(crate) async fn sync_events_v4_route(
         if duration.as_secs() > 30 {
             duration = Duration::from_secs(30);
         }
-        let _ = tokio::time::timeout(duration, watcher).await;
+        match tokio::time::timeout(duration, watcher).await {
+            Ok(x) => x.expect("watcher should succeed"),
+            Err(error) => debug!(%error, "timed out"),
+        };
     }
 
     Ok(sync_events::v4::Response {