code: function(expAst, attribute) {
          //verify that an event handler is a function call
          if (expAst && isEventHandlerAttr(attribute.name) && expAst.v !== '(') {
              this._logError("Event handler attribute only support function expressions", attribute.value[0]);
          }
      }
docs: Logs an error if the value of an event handler attribute is not a function expression.