You should format your code using the 101010 button.

After doing this I found some brackets in odd places, moved these and saved into my project with no errors. Weather it does exactly what you want it to do is a different matter and a different question...

Here is your code, reformatted and potentially fixed :

 #pragma strict
 
 var TheDamage : int = 50;
 var Distance : float;
 
 function Update() { 
 
     if (Input.GetButtonDown("Fire!")) { 
     
         var hit : RaycastHit;

         if (Physics.Raycast (transform.position, transform.TransformDirection(Vector3.forward), hit)) {
             Distance = hit.distance; 
             hit.transform.SendMessage("ApplyDamage", TheDamage, SendMessageOptions.DontRequireReceiver);
         }
     }
 }