Always require Clone for RangeQueryResult

libs/persistent_range_query/src/lib.rs

@@ -6,7 +6,9 @@ pub mod ops;
 /// Should be a monoid:
 /// * Identity element: for all a: combine(new_for_empty_range(), a) = combine(a, new_for_empty_range()) = a
 /// * Associativity: for all a, b, c: combine(combine(a, b), c) == combine(a, combine(b, c))
-pub trait RangeQueryResult<Key>: Sized {
+pub trait RangeQueryResult<Key>: Sized + Clone {
+    // Clone is equivalent to combine with an empty range.
+
     fn new_for_empty_range() -> Self;
 
     // Contract: left_range.end == right_range.start

libs/persistent_range_query/src/naive.rs

@@ -75,8 +75,6 @@ impl<
         Initializer: LazyRangeInitializer<Modification::Result, Key>,
         Key: IndexableKey,
     > VecReadableVersion<Modification, Key> for NaiveVecStorage<Modification, Initializer, Key>
-where
-    Modification::Result: Clone,
 {
     fn get(&self, keys: Range<Key>) -> Modification::Result {
         get::<Modification, Key>(&self.all_keys, &self.last_version, keys)
@@ -89,8 +87,6 @@ impl<
         Key: IndexableKey,
     > PersistentVecStorage<Modification, Initializer, Key>
     for NaiveVecStorage<Modification, Initializer, Key>
-where
-    Modification::Result: Clone,
 {
     fn new(all_keys: Range<Key>, initializer: Initializer) -> Self {
         let mut values = Vec::with_capacity(IndexableKey::index(&all_keys, &all_keys.end));

libs/persistent_range_query/src/ops/rsq.rs

@@ -18,7 +18,7 @@ impl<T> SumResult<T> {
     }
 }
 
-impl<T: for<'a> AddAssign<&'a T> + From<u8>, Key> RangeQueryResult<Key> for SumResult<T>
+impl<T: Clone + for<'a> AddAssign<&'a T> + From<u8>, Key> RangeQueryResult<Key> for SumResult<T>
 where
     for<'a> &'a T: Add<&'a T, Output = T>,
 {