Fix Clippy and compiler warnings

- Fix beta Clippy warnings
  - clippy 0.1.77 (f2048098a1c 2024-02-09)
- Fix beta compiler warnings
  - rustc 1.77.0-beta.2 (f2048098a 2024-02-09)

src/future/cache.rs

@@ -3059,7 +3059,7 @@ mod tests {
         // Note that MyError does not implement std::error::Error trait
         // like anyhow::Error.
         #[derive(Debug)]
-        pub struct MyError(String);
+        pub struct MyError(#[allow(dead_code)] String);
 
         type MyResult<T> = Result<T, Arc<MyError>>;
 
@@ -3194,7 +3194,7 @@ mod tests {
         // Note that MyError does not implement std::error::Error trait
         // like anyhow::Error.
         #[derive(Debug)]
-        pub struct MyError(String);
+        pub struct MyError(#[allow(dead_code)] String);
 
         type MyResult<T> = Result<T, Arc<MyError>>;
 

src/sync/cache.rs

@@ -3086,7 +3086,7 @@ mod tests {
         // Note that MyError does not implement std::error::Error trait like
         // anyhow::Error.
         #[derive(Debug)]
-        pub struct MyError(String);
+        pub struct MyError(#[allow(dead_code)] String);
 
         type MyResult<T> = Result<T, Arc<MyError>>;
 
@@ -3225,7 +3225,7 @@ mod tests {
         // Note that MyError does not implement std::error::Error trait like
         // anyhow::Error.
         #[derive(Debug)]
-        pub struct MyError(String);
+        pub struct MyError(#[allow(dead_code)] String);
 
         type MyResult<T> = Result<T, Arc<MyError>>;
 

src/sync/segment.rs

@@ -740,8 +740,8 @@ where
                     seg_max_capacity,
                     seg_init_capacity,
                     build_hasher.clone(),
-                    weigher.as_ref().map(Arc::clone),
-                    eviction_listener.as_ref().map(Arc::clone),
+                    weigher.clone(),
+                    eviction_listener.clone(),
                     eviction_listener_conf.clone(),
                     time_to_live,
                     time_to_idle,

src/sync_base/base_cache.rs

@@ -73,7 +73,7 @@ impl<K, V, S> Clone for BaseCache<K, V, S> {
             inner: Arc::clone(&self.inner),
             read_op_ch: self.read_op_ch.clone(),
             write_op_ch: self.write_op_ch.clone(),
-            housekeeper: self.housekeeper.as_ref().map(Arc::clone),
+            housekeeper: self.housekeeper.clone(),
         }
     }
 }

src/unsync/cache.rs

@@ -968,6 +968,9 @@ where
                     break;
                 }
 
+                // clippy::map_clone will give us a false positive warning here.
+                // Version: clippy 0.1.77 (f2048098a1c 2024-02-09) in Rust 1.77.0-beta.2
+                #[allow(clippy::map_clone)]
                 let key = probation
                     .peek_front()
                     .map(|node| Rc::clone(&node.element.key));