proxy: Handle all let underscore instances (#8898)

* Most can be simply replaced
* One instance renamed to _rtchk (return-type check)

proxy/src/cache/endpoints.rs

@@ -242,6 +242,6 @@ mod tests {
     #[test]
     fn test() {
         let s = "{\"branch_created\":null,\"endpoint_created\":{\"endpoint_id\":\"ep-rapid-thunder-w0qqw2q9\"},\"project_created\":null,\"type\":\"endpoint_created\"}";
-        let _: ControlPlaneEventKey = serde_json::from_str(s).unwrap();
+        serde_json::from_str::<ControlPlaneEventKey>(s).unwrap();
     }
 }

proxy/src/console/messages.rs

@@ -395,7 +395,7 @@ mod tests {
                 }
             }
         });
-        let _: KickSession<'_> = serde_json::from_str(&json.to_string())?;
+        serde_json::from_str::<KickSession<'_>>(&json.to_string())?;
 
         Ok(())
     }
@@ -403,7 +403,7 @@ mod tests {
     #[test]
     fn parse_db_info() -> anyhow::Result<()> {
         // with password
-        let _: DatabaseInfo = serde_json::from_value(json!({
+        serde_json::from_value::<DatabaseInfo>(json!({
             "host": "localhost",
             "port": 5432,
             "dbname": "postgres",
@@ -413,7 +413,7 @@ mod tests {
         }))?;
 
         // without password
-        let _: DatabaseInfo = serde_json::from_value(json!({
+        serde_json::from_value::<DatabaseInfo>(json!({
             "host": "localhost",
             "port": 5432,
             "dbname": "postgres",
@@ -422,7 +422,7 @@ mod tests {
         }))?;
 
         // new field (forward compatibility)
-        let _: DatabaseInfo = serde_json::from_value(json!({
+        serde_json::from_value::<DatabaseInfo>(json!({
             "host": "localhost",
             "port": 5432,
             "dbname": "postgres",
@@ -441,7 +441,7 @@ mod tests {
             "address": "0.0.0.0",
             "aux": dummy_aux(),
         });
-        let _: WakeCompute = serde_json::from_str(&json.to_string())?;
+        serde_json::from_str::<WakeCompute>(&json.to_string())?;
         Ok(())
     }
 
@@ -451,18 +451,18 @@ mod tests {
         let json = json!({
             "role_secret": "secret",
         });
-        let _: GetRoleSecret = serde_json::from_str(&json.to_string())?;
+        serde_json::from_str::<GetRoleSecret>(&json.to_string())?;
         let json = json!({
             "role_secret": "secret",
             "allowed_ips": ["8.8.8.8"],
         });
-        let _: GetRoleSecret = serde_json::from_str(&json.to_string())?;
+        serde_json::from_str::<GetRoleSecret>(&json.to_string())?;
         let json = json!({
             "role_secret": "secret",
             "allowed_ips": ["8.8.8.8"],
             "project_id": "project",
         });
-        let _: GetRoleSecret = serde_json::from_str(&json.to_string())?;
+        serde_json::from_str::<GetRoleSecret>(&json.to_string())?;
 
         Ok(())
     }

proxy/src/context.rs

@@ -6,7 +6,7 @@ use pq_proto::StartupMessageParams;
 use smol_str::SmolStr;
 use std::net::IpAddr;
 use tokio::sync::mpsc;
-use tracing::{field::display, info, info_span, Span};
+use tracing::{debug, field::display, info, info_span, Span};
 use try_lock::TryLock;
 use uuid::Uuid;
 
@@ -362,7 +362,9 @@ impl RequestMonitoringInner {
                 });
         }
         if let Some(tx) = self.sender.take() {
-            let _: Result<(), _> = tx.send(RequestData::from(&*self));
+            tx.send(RequestData::from(&*self))
+                .inspect_err(|e| debug!("tx send failed: {e}"))
+                .ok();
         }
     }
 
@@ -371,7 +373,9 @@ impl RequestMonitoringInner {
         // Here we log the length of the session.
         self.disconnect_timestamp = Some(Utc::now());
         if let Some(tx) = self.disconnect_sender.take() {
-            let _: Result<(), _> = tx.send(RequestData::from(&*self));
+            tx.send(RequestData::from(&*self))
+                .inspect_err(|e| debug!("tx send failed: {e}"))
+                .ok();
         }
     }
 }

proxy/src/context/parquet.rs

@@ -290,7 +290,7 @@ async fn worker_inner(
     }
 
     if !w.flushed_row_groups().is_empty() {
-        let _: Writer<BytesMut> = upload_parquet(w, len, &storage).await?;
+        let _rtchk: Writer<BytesMut> = upload_parquet(w, len, &storage).await?;
     }
 
     Ok(())

proxy/src/lib.rs

@@ -3,7 +3,7 @@
 #![deny(
     deprecated,
     future_incompatible,
-    // TODO: consider let_underscore
+    let_underscore,
     nonstandard_style,
     rust_2024_compatibility
 )]

proxy/src/proxy/tests.rs

@@ -268,7 +268,7 @@ async fn keepalive_is_inherited() -> anyhow::Result<()> {
         anyhow::Ok(keepalive)
     });
 
-    let _ = TcpStream::connect(("127.0.0.1", port)).await?;
+    TcpStream::connect(("127.0.0.1", port)).await?;
     assert!(t.await??, "keepalive should be inherited");
 
     Ok(())

proxy/src/redis/connection_with_credentials_provider.rs

@@ -6,7 +6,7 @@ use redis::{
     ConnectionInfo, IntoConnectionInfo, RedisConnectionInfo, RedisResult,
 };
 use tokio::task::JoinHandle;
-use tracing::{error, info};
+use tracing::{debug, error, info};
 
 use super::elasticache::CredentialsProvider;
 
@@ -109,7 +109,10 @@ impl ConnectionWithCredentialsProvider {
             let credentials_provider = credentials_provider.clone();
             let con2 = con.clone();
             let f = tokio::spawn(async move {
-                let _ = Self::keep_connection(con2, credentials_provider).await;
+                Self::keep_connection(con2, credentials_provider)
+                    .await
+                    .inspect_err(|e| debug!("keep_connection failed: {e}"))
+                    .ok();
             });
             self.refresh_token_task = Some(f);
         }

proxy/src/stream.rs

@@ -12,6 +12,7 @@ use std::{io, task};
 use thiserror::Error;
 use tokio::io::{AsyncRead, AsyncWrite, ReadBuf};
 use tokio_rustls::server::TlsStream;
+use tracing::debug;
 
 /// Stream wrapper which implements libpq's protocol.
 ///
@@ -138,9 +139,10 @@ impl<S: AsyncWrite + Unpin> PqStream<S> {
         );
 
         // already error case, ignore client IO error
-        let _: Result<_, std::io::Error> = self
-            .write_message(&BeMessage::ErrorResponse(msg, None))
-            .await;
+        self.write_message(&BeMessage::ErrorResponse(msg, None))
+            .await
+            .inspect_err(|e| debug!("write_message failed: {e}"))
+            .ok();
 
         Err(ReportedError {
             source: anyhow::anyhow!(msg),
@@ -164,9 +166,10 @@ impl<S: AsyncWrite + Unpin> PqStream<S> {
         );
 
         // already error case, ignore client IO error
-        let _: Result<_, std::io::Error> = self
-            .write_message(&BeMessage::ErrorResponse(&msg, None))
-            .await;
+        self.write_message(&BeMessage::ErrorResponse(&msg, None))
+            .await
+            .inspect_err(|e| debug!("write_message failed: {e}"))
+            .ok();
 
         Err(ReportedError {
             source: anyhow::anyhow!(error),

proxy/src/url.rs

@@ -57,7 +57,7 @@ mod tests {
     fn bad_url() {
         let url = "test:foobar";
         url.parse::<url::Url>().expect("unexpected parsing failure");
-        let _ = url.parse::<ApiUrl>().expect_err("should not parse");
+        url.parse::<ApiUrl>().expect_err("should not parse");
     }
 
     #[test]