Make ATreeNode.getChildren return an immutable list to improve code safety.

Author: lm-sousa

SpecsUtils/src/pt/up/fe/specs/util/treenode/ATreeNode.java

@@ -72,8 +72,11 @@ private List<K> initChildren(Collection<? extends K> children) {
      */
     @Override
     public List<K> getChildren() {
-        // FIXME: Should be 'Collections.unmodifiableList(this.children);'
-        // but the current implementation breaks when you do.
+        return Collections.unmodifiableList(this.children);
+    }
+
+    @Override
+    public List<K> getChildrenMutable() {
         return this.children;
     }
 

SpecsUtils/src/pt/up/fe/specs/util/treenode/ChildrenIterator.java

@@ -25,8 +25,8 @@ public class ChildrenIterator<N extends TreeNode<N>> implements ListIterator<N>
     public ChildrenIterator(TreeNode<N> parent) {
 
         this.parent = parent;
-        // Currently cannot enforce immutable children view due to MATISSE passes
-        this.iterator = parent.getChildren().listIterator();
+        // Access internal mutable list for modification operations
+        this.iterator = parent.getChildrenMutable().listIterator();
 
         this.lastReturned = null;
     }

SpecsUtils/src/pt/up/fe/specs/util/treenode/TreeNode.java

@@ -169,6 +169,14 @@ default K getChild(int index1, int index2, int... indexes) {
      */
     List<K> getChildren();
 
+    /**
+     * Returns a mutable list of children for internal use only.
+     * Should only be used by ChildrenIterator and internal tree operations.
+     *
+     * @return the mutable children list
+     */
+    List<K> getChildrenMutable();
+
     /**
      * TODO: Rename to castChildren.
      *