fix types for unbox, set-box!, etc.

Author: AlexKnauth

typed-racket-lib/typed-racket/base-env/base-env.rkt

@@ -868,17 +868,17 @@
 [box (-poly (a) (a . -> . (-box a)))]
 [box-immutable (-poly (a) (a . -> . (-Read-Only-Boxof a)))]
 [unbox (-poly (a) (cl->*
-                   ((-box a) . -> . a)
+                   ((-box -Bottom a) . -> . a)
                    ((make-BoxTop) . -> . Univ)))]
-[set-box! (-poly (a) ((-box a) a . -> . -Void))]
+[set-box! (-poly (a) ((-box a Univ) a . -> . -Void))]
 [unsafe-unbox (-poly (a) (cl->*
-                          ((-box a) . -> . a)
+                          ((-box -Bottom a) . -> . a)
                           ((make-BoxTop) . -> . Univ)))]
-[unsafe-set-box! (-poly (a) ((-box a) a . -> . -Void))]
+[unsafe-set-box! (-poly (a) ((-box a Univ) a . -> . -Void))]
 [unsafe-unbox* (-poly (a) (cl->*
-                           ((-box a) . -> . a)
+                           ((-box -Bottom a) . -> . a)
                            ((make-BoxTop) . -> . Univ)))]
-[unsafe-set-box*! (-poly (a) ((-box a) a . -> . -Void))]
+[unsafe-set-box*! (-poly (a) ((-box a Univ) a . -> . -Void))]
 [box? (make-pred-ty (make-BoxTop))]
 
 ;; Section 4.13 (Hash Tables)