code: public void addClassNode(ClassNode node) {
          ModuleNode module = new ModuleNode(this.ast);
          this.ast.addModule(module);
          module.addClass(node);
      }
docs: Adds a ClassNode directly to the unit (ie. without source).
  WARNING: the source is needed for error reporting, using
  this method without setting a SourceUnit will cause
  NullPinterExceptions