# Pastebin FaXGRJcL
shawnw: 
#lang typed/racket

(require compatibility/mlist)
(: clist (MListof Number))
(define clist (mcons (ann 1 Number) (mcons (ann 2 Number) (ann null (MListof Number)))))

(set-mcdr! (mcdr clist) clist)

clist