问装饰器不是函数-角度2

EN

import { Directive, OnInit, OnDestroy, Input, Output, HostBinding,
    EventEmitter, ElementRef, ContentChildren, ViewChildren,
    Query, QueryList } from '@angular/core';
import { DropdownMenuInterface } from './dropdown.interface';
import { DropdownToggleInterface } from './dropdown.interface';
import { dropdownService, NONINPUT} from './dropdown.service';

@Directive({selector: '[dropdown]'})
export class Dropdown implements OnInit, OnDestroy {

    ......

    // index of selected element
    public selectedOption:number;
    // drop menu html
    public menuEl:ElementRef;
    // drop down toggle element
    public toggleEl:ElementRef;

    dropdownMenuList: QueryList<ElementRef>;

    constructor(public el:ElementRef,
       @Query('dropdownMenu') dropdownMenuList: QueryList<ElementRef>) {
     }

     public set isOpen(value) {
     this._isOpen = !!value;

   .....