Port common, and most of crypto, to a more aggressive clippy

common/db/src/lib.rs

@@ -1,6 +1,8 @@
 use core::fmt::Debug;
+extern crate alloc;
+use alloc::sync::Arc;
 use std::{
-  sync::{Arc, RwLock},
+  sync::RwLock,
   collections::{HashSet, HashMap},
 };
 
@@ -23,7 +25,7 @@ pub trait Db: 'static + Send + Sync + Clone + Debug + Get {
   fn key(db_dst: &'static [u8], item_dst: &'static [u8], key: impl AsRef<[u8]>) -> Vec<u8> {
     let db_len = u8::try_from(db_dst.len()).unwrap();
     let dst_len = u8::try_from(item_dst.len()).unwrap();
-    [[db_len].as_ref(), db_dst, [dst_len].as_ref(), item_dst, key.as_ref()].concat().to_vec()
+    [[db_len].as_ref(), db_dst, [dst_len].as_ref(), item_dst, key.as_ref()].concat()
   }
   fn txn(&mut self) -> Self::Transaction<'_>;
 }
@@ -38,7 +40,7 @@ impl<'a> Get for MemDbTxn<'a> {
     if self.2.contains(key.as_ref()) {
       return None;
     }
-    self.1.get(key.as_ref()).cloned().or(self.0 .0.read().unwrap().get(key.as_ref()).cloned())
+    self.1.get(key.as_ref()).cloned().or_else(|| self.0 .0.read().unwrap().get(key.as_ref()).cloned())
   }
 }
 impl<'a> DbTxn for MemDbTxn<'a> {
@@ -66,22 +68,23 @@ impl<'a> DbTxn for MemDbTxn<'a> {
 pub struct MemDb(Arc<RwLock<HashMap<Vec<u8>, Vec<u8>>>>);
 
 impl PartialEq for MemDb {
-  fn eq(&self, other: &MemDb) -> bool {
+  fn eq(&self, other: &Self) -> bool {
     *self.0.read().unwrap() == *other.0.read().unwrap()
   }
 }
 impl Eq for MemDb {}
 
 impl Default for MemDb {
-  fn default() -> MemDb {
-    MemDb(Arc::new(RwLock::new(HashMap::new())))
+  fn default() -> Self {
+    Self(Arc::new(RwLock::new(HashMap::new())))
   }
 }
 
 impl MemDb {
   /// Create a new in-memory database.
-  pub fn new() -> MemDb {
-    MemDb::default()
+  #[must_use]
+  pub fn new() -> Self {
+    Self::default()
   }
 }