意外符号 CS1525 变量名称

我已经修改了一些代码以满足我的需求。虽然变量"dest"应该是一个局部变量（我认为），那么为什么在为dest分配值的行上会出现一个错误，并带有"意外的符号'dest'"错误，我将如何解决它？（这是链接：http://noobtuts.com/unity/2d-pacman-game）

using UnityEngine;
using System.Collections;
public class SepticSamMove : MonoBehaviour 
{
    public float speed = 0.4f;
    Vector2 dest = Vector2.zero;
    // Use this for initialization
    void Start () 
    {
        dest = transform.position; 
    }
    // Update is called once per frame
    void FixedUpdate () 
    {
        //move closer to Destination
        Vector2 p =Vector2.MoveTowards(transform.position,dest,speed);
        GetComponent<Rigidbody2D> ().MovePosition (p);
        //check input for movement
        if ((Vector2)transform.position == dest)
        {
            //up
            if(Input.GetKey(KeyCode.W) && valid(Vector2.up)
                dest = (Vector2)transform.position+Vector2.up;
            if(Input.GetKey(KeyCode.S) && vaild(-Vector2.up)
                dest = (Vector2)transform.position - Vector2.up;
            if(Input.GetKey(KeyCode.D) && valid(Vector2.right)
                dest = (Vector2)transform.position+Vector2.right;
            if(Input.GetKey(KeyCode.A) && valid(-Vector2.right)
                dest =(Vector2)transform.position-Vector2.right;
        }

        // Animation Parameters
        Vector2 dir = dest - (Vector2)transform.position;
        GetComponent<Animator>().SetFloat("DirX", dir.x);
        GetComponent<Animator>().SetFloat("DirY", dir.y);
    }
    bool vaild (Vector2 dir)
    {
        //cast Line from 'Next to Septic Sam' to SepticSam
        Vector2 pos= transform.position;
        RaycastHit2D hit = Physics2D.Linecast (pos + dir, pos);
        return (hit.collider == GetComponent<Collider2D> ());
    }
}