use an option rather than ManuallyDrop

crates/storage/db-api/src/cursor.rs

@@ -1,7 +1,6 @@
 use std::{
     cell::Cell,
     fmt,
-    mem::ManuallyDrop,
     ops::{Bound, RangeBounds},
 };
 
@@ -377,7 +376,7 @@ impl<T: DupSort, CURSOR: DbDupCursorRO<T>> Iterator for DupWalker<'_, T, CURSOR>
 /// This allows cursors to be reused across multiple operations,
 /// reducing the overhead of repeatedly creating new cursors.
 pub struct ReusableCursor<'tx, 'cell, T: Table, C: DbCursorRO<T>> {
-    cursor: ManuallyDrop<C>,
+    cursor: Option<C>,
     cell: &'cell Cell<Option<C>>,
     _phantom: std::marker::PhantomData<&'tx T>,
 }
@@ -395,16 +394,13 @@ where
 impl<'tx, 'cell, T: Table, C: DbCursorRO<T>> ReusableCursor<'tx, 'cell, T, C> {
     /// Creates a new `ReusableCursor` from a cursor and a cell to return it to.
     pub const fn new(cursor: C, cell: &'cell Cell<Option<C>>) -> Self {
-        Self { cursor: ManuallyDrop::new(cursor), cell, _phantom: std::marker::PhantomData }
+        Self { cursor: Some(cursor), cell, _phantom: std::marker::PhantomData }
     }
 }
 
 impl<'tx, 'cell, T: Table, C: DbCursorRO<T>> Drop for ReusableCursor<'tx, 'cell, T, C> {
     fn drop(&mut self) {
-        // SAFETY: We take ownership of the cursor and return it to the cell.
-        // The cursor won't be dropped automatically due to ManuallyDrop.
-        let cursor = unsafe { ManuallyDrop::take(&mut self.cursor) };
-        self.cell.set(Some(cursor));
+        self.cell.set(self.cursor.take());
     }
 }
 
@@ -412,7 +408,7 @@ impl<'tx, 'cell, T: Table, C: DbCursorRO<T>> std::ops::Deref for ReusableCursor<
     type Target = C;
 
     fn deref(&self) -> &Self::Target {
-        &self.cursor
+        self.cursor.as_ref().expect("cursor always exists")
     }
 }
 
@@ -420,6 +416,6 @@ impl<'tx, 'cell, T: Table, C: DbCursorRO<T>> std::ops::DerefMut
     for ReusableCursor<'tx, 'cell, T, C>
 {
     fn deref_mut(&mut self) -> &mut Self::Target {
-        &mut self.cursor
+        self.cursor.as_mut().expect("cursor always exists")
     }
 }