source location wrong in runtime error

[rfindler]

In this program:

#lang dssl2

class C:
     let fd
     def __init__(self):
         self.fd == None
         
C()

the error message points inside the class system. Changing this code to:

(syntax/loc stx ...)

where the ellipses has what's currently on those lines (minus the #') seems to fix the issue.