不理解valid方法参数里的vector2 dir是以怎样的逻辑获得向量的？

以我的理解valid是方法，返回的是bool类型，那么方法参数里不应该是bool类型的吗？

主要不明白dir为什么可以通过按键控制获得x,y的坐标。

using UnityEngine;

public class PacmanMove : MonoBehaviour {

    private float speed = 0.25f;
    private Vector2 dest = Vector2.zero;

    private void Start()
    {
        dest = transform.position;        
    }

    private void FixedUpdate()
    {        
        Vector2 temp = Vector2.MoveTowards(transform.position, dest, speed);        
        GetComponent<Rigidbody2D>().MovePosition(temp);
        if (Input.GetKey(KeyCode.B)) {
            
        }
        if ((Vector2)transform.position == dest) {
            if ((Input.GetKey(KeyCode.W) || Input.GetKey(KeyCode.UpArrow))&&Valid(Vector2.up))
            {
                dest = (Vector2)transform.position + Vector2.up;
                
            }
            if ((Input.GetKey(KeyCode.A) || Input.GetKey(KeyCode.LeftArrow)) && Valid(Vector2.left))
            {
                dest = (Vector2)transform.position + Vector2.left;
            }
            if ((Input.GetKey(KeyCode.S) || Input.GetKey(KeyCode.DownArrow)) && Valid(Vector2.down))
            {
                dest = (Vector2)transform.position + Vector2.down;
            }
            if ((Input.GetKey(KeyCode.D) || Input.GetKey(KeyCode.RightArrow)) && Valid(Vector2.right))
            {
                dest = (Vector2)transform.position + Vector2.right;
            }
        }
         
    }
    private bool Valid(Vector2 dir) {
        Vector2 pos = transform.position;
        RaycastHit2D hit = Physics2D.Linecast(pos+dir, pos);
        Debug.Log(dir);
        return (hit.collider == GetComponent<Collider2D>());
    }
}