templatizing type system

Author: Arshia Malkani

src/main/java/net/sf/jsqlparser/expression/Expression.java

@@ -26,5 +26,13 @@ public interface Expression {
     void setExpressionType(String expression);
     String getExpressionType();
 
+    public class Box<T> {
+        private T t;
+        public void set(T t) { this.t = t; }
+        public T get() { return t; }
+    }
+
+    Box resolvedExpressionType = null;
+
     void accept(ExpressionVisitor expressionVisitor);
 }