Don't panic when dropping StaticSnapshot, and implement Clone

src/merk/snapshot.rs

@@ -1,7 +1,5 @@
 use std::{cell::Cell, mem::ManuallyDrop};
 
-use ed::{Decode, Encode};
-
 use crate::{
  proofs::{query::QueryItem, Query},
  tree::{Fetch, RefWalker, Tree, NULL_HASH},
@@ -118,13 +116,9 @@ impl StaticSnapshot {
  };
  let db_ss: rocksdb::Snapshot<'a> = std::mem::transmute(db_ss);
 
- let tree = self.tree.take().unwrap();
- let tree_clone = Tree::decode(tree.key().to_vec(), tree.encode().as_slice());
- self.tree.set(Some(tree));
-
  ManuallyDrop::new(Snapshot {
  ss: db_ss,
- tree: Cell::new(Some(tree_clone)),
+ tree: self.clone_tree(),
  })
  }
 
@@ -133,10 +127,29 @@ impl StaticSnapshot {
  ManuallyDrop::drop(&mut ss);
  std::mem::forget(self);
  }
+
+ fn clone_tree(&self) -> Cell<Option<Tree>> {
+ let tree = self.tree.take().unwrap();
+ let tree_clone = Cell::new(Some(Tree::decode(
+ tree.key().to_vec(),
+ tree.encode().as_slice(),
+ )));
+ self.tree.set(Some(tree));
+ tree_clone
+ }
 }
 
 impl Drop for StaticSnapshot {
  fn drop(&mut self) {
- panic!("StaticSnapshot must be manually dropped");
+ log::debug!("StaticSnapshot must be manually dropped");
+ }
+}
+
+impl Clone for StaticSnapshot {
+ fn clone(&self) -> Self {
+ Self {
+ tree: self.clone_tree(),
+ inner: self.inner,
+ }
  }
 }