Merge Tree branch

apps/tree/expression_reference.cpp

@@ -0,0 +1,12 @@
+#include "expression_reference.h"
+#include "allocation_failed_expression_node.h"
+
+template<>
+TreeNode * ExpressionRef::FailedAllocationStaticNode() {
+  static AllocationFailedExpressionNode FailureNode;
+  if (FailureNode.identifier() >= -1) {
+    int newIdentifier = TreePool::sharedPool()->registerStaticNode(&FailureNode);
+    FailureNode.rename(newIdentifier);
+  }
+  return &FailureNode;
+}