trying to get this loop to work. C# error CS0201: Only assignment, call, increment, decrement, and new object expressions can be used as a statement

trying to get this loop to work for fire rate, using UnityEngine; using System.Collections;

 public class PlayerFighter : MonoBehaviour {
 
     public GameObject MachGunBullets;
     public GameObject Missiles;
 
     public int MissilesAmmount = 3;
     public int Armor = 5;
     public int Lives = 3;
     public int PowerLevel = 1;
     public float waittillnextfire = 0;
     public float firespeed = 2;
 
 //-----------------------------------------------------------------------------------------------------------------------
     void Update () {
         
         //player Controlls
         if (Input.GetButton("z"))
             if (waittillnextfire == 0) {
                  Instantiate (MachGunBullets, transform.position, transform.rotation);
             waittillnextfire == 1;
             }
         waittillnextfire -= Time.deltaTime * firespeed;
 
         }
 
 }