fix: fetching outer values before calling inner nodes (#1965)

Companion for TimefoldAI/timefold-solver-enterprise#397

Author: zepfred

core/src/main/java/ai/timefold/solver/core/impl/heuristic/selector/move/generic/list/RandomSubListChangeMoveIterator.java

@@ -34,11 +34,14 @@ class RandomSubListChangeMoveIterator<Solution_> extends UpcomingSelectionIterat
 
     @Override
     protected Move<Solution_> createUpcomingSelection() {
-        if (!subListIterator.hasNext() || !destinationIterator.hasNext()) {
+        if (!subListIterator.hasNext()) {
             return noUpcomingSelection();
         }
-
+        // The inner node may need the outer iterator to select the next value first
         var subList = subListIterator.next();
+        if (!destinationIterator.hasNext()) {
+            return noUpcomingSelection();
+        }
         var destination = findUnpinnedDestination(destinationIterator, listVariableDescriptor);
         if (destination == null) {
             return noUpcomingSelection();

core/src/main/java/ai/timefold/solver/core/impl/heuristic/selector/move/generic/list/kopt/KOptListMoveIterator.java

@@ -72,15 +72,14 @@ private Move<Solution_> pickTwoOptMove() {
         if (!originIterator.hasNext()) {
             return NoChangeMove.getInstance();
         }
+        // The inner node may need the outer iterator to select the next value first
+        Object firstValue = originIterator.next();
         @SuppressWarnings("unchecked")
         var valueIterator = (Iterator<Node_>) valueSelector.iterator();
         if (!valueIterator.hasNext()) {
             return NoChangeMove.getInstance();
         }
-
-        Object firstValue = originIterator.next();
         Object secondValue = valueIterator.next();
-
         var firstElementPosition = listVariableStateSupply.getElementPosition(firstValue)
                 .ensureAssigned();
         var secondElementPosition = listVariableStateSupply.getElementPosition(secondValue)