for (int i = 0; i < node.jjtGetNumChildren(); i++) {
Node projElem = node.jjtGetChild(i);
assert projElem instanceof ASTProjectionElem : "child node is not a projection element";
Object result = projElem.jjtAccept(this, aliases);
if (result instanceof String) {
String alias = (String)result;
boolean isUnique = aliases.add(alias);