diff --git a/src/api.rs b/src/api.rs
index 374fa48c..64f28b42 100644
--- a/src/api.rs
+++ b/src/api.rs
@@ -44,19 +44,19 @@ impl<F: Fn(&mut T, U) + 'static, T, U> ObjectSetCallback<T, U> for F {}
 
 #[cfg(feature = "sync")]
 pub trait IteratorCallback:
-    Fn(&Dynamic) -> Box<dyn Iterator<Item = Dynamic>> + Send + Sync + 'static
+    Fn(Dynamic) -> Box<dyn Iterator<Item = Dynamic>> + Send + Sync + 'static
 {
 }
 #[cfg(feature = "sync")]
-impl<F: Fn(&Dynamic) -> Box<dyn Iterator<Item = Dynamic>> + Send + Sync + 'static> IteratorCallback
+impl<F: Fn(Dynamic) -> Box<dyn Iterator<Item = Dynamic>> + Send + Sync + 'static> IteratorCallback
     for F
 {
 }
 
 #[cfg(not(feature = "sync"))]
-pub trait IteratorCallback: Fn(&Dynamic) -> Box<dyn Iterator<Item = Dynamic>> + 'static {}
+pub trait IteratorCallback: Fn(Dynamic) -> Box<dyn Iterator<Item = Dynamic>> + 'static {}
 #[cfg(not(feature = "sync"))]
-impl<F: Fn(&Dynamic) -> Box<dyn Iterator<Item = Dynamic>> + 'static> IteratorCallback for F {}
+impl<F: Fn(Dynamic) -> Box<dyn Iterator<Item = Dynamic>> + 'static> IteratorCallback for F {}
 
 /// Engine public API
 impl Engine {
diff --git a/src/engine.rs b/src/engine.rs
index aa6a8baa..b3ed775d 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -49,9 +49,9 @@ pub type FnAny =
 pub type FnAny = dyn Fn(&mut FnCallArgs, Position) -> Result<Dynamic, Box<EvalAltResult>>;
 
 #[cfg(feature = "sync")]
-pub type IteratorFn = dyn Fn(&Dynamic) -> Box<dyn Iterator<Item = Dynamic>> + Send + Sync;
+pub type IteratorFn = dyn Fn(Dynamic) -> Box<dyn Iterator<Item = Dynamic>> + Send + Sync;
 #[cfg(not(feature = "sync"))]
-pub type IteratorFn = dyn Fn(&Dynamic) -> Box<dyn Iterator<Item = Dynamic>>;
+pub type IteratorFn = dyn Fn(Dynamic) -> Box<dyn Iterator<Item = Dynamic>>;
 
 #[cfg(debug_assertions)]
 pub const MAX_CALL_STACK_DEPTH: usize = 28;
@@ -1608,8 +1608,7 @@ impl Engine {
                         .find(|pkg| pkg.type_iterators.contains_key(&tid))
                         .and_then(|pkg| pkg.type_iterators.get(&tid))
                 }) {
-                    // Add the loop variable - variable name is copied
-                    // TODO - avoid copying variable name
+                    // Add the loop variable
                     scope.push(name.clone(), ());
 
                     let entry = ScopeSource {
@@ -1618,7 +1617,7 @@ impl Engine {
                         typ: ScopeEntryType::Normal,
                     };
 
-                    for a in iter_fn(&arr) {
+                    for a in iter_fn(arr) {
                         *scope.get_mut(entry) = a;
 
                         match self.eval_stmt(scope, fn_lib, body, level) {
diff --git a/src/packages/array_basic.rs b/src/packages/array_basic.rs
index b00f012c..ca69f3fc 100644
--- a/src/packages/array_basic.rs
+++ b/src/packages/array_basic.rs
@@ -116,8 +116,8 @@ def_package!(crate:BasicArrayPackage:"Basic array utilities.", lib, {
     // Register array iterator
     lib.type_iterators.insert(
         TypeId::of::<Array>(),
-        Box::new(|a: &Dynamic| {
-            Box::new(a.downcast_ref::<Array>().unwrap().clone().into_iter())
+        Box::new(|a: Dynamic| {
+            Box::new(a.cast::<Array>().into_iter())
                 as Box<dyn Iterator<Item = Dynamic>>
         }),
     );
diff --git a/src/packages/iter_basic.rs b/src/packages/iter_basic.rs
index af2e6f53..9672d61c 100644
--- a/src/packages/iter_basic.rs
+++ b/src/packages/iter_basic.rs
@@ -19,14 +19,9 @@ where
 {
     lib.type_iterators.insert(
         TypeId::of::<Range<T>>(),
-        Box::new(|source: &Dynamic| {
-            Box::new(
-                source
-                    .downcast_ref::<Range<T>>()
-                    .cloned()
-                    .unwrap()
-                    .map(|x| x.into_dynamic()),
-            ) as Box<dyn Iterator<Item = Dynamic>>
+        Box::new(|source: Dynamic| {
+            Box::new(source.cast::<Range<T>>().map(|x| x.into_dynamic()))
+                as Box<dyn Iterator<Item = Dynamic>>
         }),
     );
 }
@@ -64,14 +59,9 @@ where
 {
     lib.type_iterators.insert(
         TypeId::of::<StepRange<T>>(),
-        Box::new(|source: &Dynamic| {
-            Box::new(
-                source
-                    .downcast_ref::<StepRange<T>>()
-                    .cloned()
-                    .unwrap()
-                    .map(|x| x.into_dynamic()),
-            ) as Box<dyn Iterator<Item = Dynamic>>
+        Box::new(|source: Dynamic| {
+            Box::new(source.cast::<StepRange<T>>().map(|x| x.into_dynamic()))
+                as Box<dyn Iterator<Item = Dynamic>>
         }),
     );
 }