Collider.Raycast  

function Raycast (ray : Ray, out hitInfo : RaycastHit, distance : float) : boolean

Parameters

Returns

boolean - True when the ray intersects any collider, otherwise false.

Description

Casts a Ray that ignores all Colliders except this one.

Same as above using ray.origin and ray.direction instead of origin and direction.

// pragma below is needed due to a UnityJS issue
#pragma strict

function Update(){
    var ray : Ray = Camera.main.ScreenPointToRay (Input.mousePosition);
    var hit : RaycastHit;
    if (collider.Raycast (ray, hit, 100.0)) {
        Debug.DrawLine (ray.origin, hit.point);
    }
}