AddExpression add1 = new AddExpression(expPlan, constant1, constant2);
CastExpression cast1 = new CastExpression(expPlan,constant3, createFS(DataType.DOUBLE));
MultiplyExpression mul1 = new MultiplyExpression(expPlan, add1, cast1);
CompilationMessageCollector collector = new CompilationMessageCollector();
TypeCheckingExpVisitor expTypeChecker = new TypeCheckingExpVisitor(expPlan, collector, null);
expTypeChecker.visit();
printMessageCollector(collector);
//printTypeGraph(plan);
if (collector.hasError()) {
throw new Exception("Error during type checking");