diff --git a/chain/src/consume_orphan.rs b/chain/src/consume_orphan.rs
index 8bcedc3a76..612d7ae582 100644
--- a/chain/src/consume_orphan.rs
+++ b/chain/src/consume_orphan.rs
@@ -3,7 +3,7 @@
 use crate::utils::orphan_block_pool::OrphanBlockPool;
 use crate::{LonelyBlock, LonelyBlockHash};
 use ckb_channel::{select, Receiver, Sender};
-use ckb_error::{Error, InternalErrorKind};
+use ckb_error::Error;
 use ckb_logger::internal::trace;
 use ckb_logger::{debug, error, info};
 use ckb_shared::block_status::BlockStatus;
diff --git a/chain/src/utils/orphan_block_pool.rs b/chain/src/utils/orphan_block_pool.rs
index 7556f6d6c7..ff6dd63b49 100644
--- a/chain/src/utils/orphan_block_pool.rs
+++ b/chain/src/utils/orphan_block_pool.rs
@@ -38,7 +38,7 @@ impl InnerPool {
         let parent_hash = lonely_block.block().data().header().raw().parent_hash();
         self.blocks
             .entry(parent_hash.clone())
-            .or_insert_with(HashMap::default)
+            .or_default()
             .insert(hash.clone(), lonely_block);
         // Out-of-order insertion needs to be deduplicated
         self.leaders.remove(&hash);
diff --git a/util/metrics/src/lib.rs b/util/metrics/src/lib.rs
index 990a8b0800..1cd4827d68 100644
--- a/util/metrics/src/lib.rs
+++ b/util/metrics/src/lib.rs
@@ -6,10 +6,6 @@
 //!
 //! [`ckb-metrics-service`]: ../ckb_metrics_service/index.html
 
-use prometheus::{
-    register_histogram, register_histogram_vec, register_int_counter, register_int_gauge,
-    register_int_gauge_vec, Histogram, HistogramVec, IntCounter, IntGauge, IntGaugeVec,
-};
 use prometheus_static_metric::make_static_metric;
 use std::cell::Cell;