chore: Initialize copy array from previous values in array_set (#2106)

* Initialize copy array from previous values in array_set

* chore: use `try_vecmap` in place of for-loop

* Update crates/noirc_evaluator/src/ssa_refactor/acir_gen/mod.rs

* Update crates/noirc_evaluator/src/ssa_refactor/acir_gen/mod.rs

---------

Co-authored-by: Tom French <[email protected]>
Co-authored-by: jfecher <[email protected]>

crates/noirc_evaluator/src/ssa/acir_gen/mod.rs

@@ -589,19 +589,17 @@ impl Context {
         let result_array_id = result_id.to_usize() as u32;
         let result_block_id = BlockId(result_array_id);
 
-        // Initialize the new array with zero values
-        self.initialize_array(result_block_id, len, None)?;
-
-        // Copy the values from the old array into the newly created zeroed array
-        for i in 0..len {
+        // Initialize the new array with the values from the old array
+        let init_values = try_vecmap(0..len, |i| {
             let index = AcirValue::Var(
                 self.acir_context.add_constant(FieldElement::from(i as u128)),
                 AcirType::NumericType(NumericType::NativeField),
             );
             let var = index.into_var()?;
             let read = self.acir_context.read_from_memory(block_id, &var)?;
-            self.acir_context.write_to_memory(result_block_id, &var, &read)?;
-        }
+            Ok(AcirValue::Var(read, AcirType::NumericType(NumericType::NativeField)))
+        })?;
+        self.initialize_array(result_block_id, len, Some(&init_values))?;
 
         // Write the new value into the new array at the specified index
         let index_var = self.convert_value(index, dfg).into_var()?;