fix problems with references to bindings at higher phases

original commit: 577cf4592e

collects/compiler/zo-marshal.rkt

@@ -610,7 +610,8 @@
         (out-anything modidx out)
         (out-anything sym out)
         (unless (zero? phase)
-          (out-number -2 out))
+          (out-number -2 out)
+          (out-number phase out))
         (out-number pos out)]
        [(struct closure (lam gen-id))
         (out-byte CPT_CLOSURE out)

collects/compiler/zo-parse.rkt

@@ -859,7 +859,7 @@
                [pos (read-compact-number cp)])
            (let-values ([(mod-phase pos)
                          (if (= pos -2)
-                           (values 1 (read-compact-number cp))
+                           (values (read-compact-number cp) (read-compact-number cp))
                            (values 0 pos))])
              (make-module-variable mod var pos mod-phase)))]
         [(local-unbox)

collects/compiler/zo-structs.rkt

@@ -43,7 +43,7 @@
 (define-form-struct module-variable ([modidx module-path-index?] 
                                      [sym symbol?] 
                                      [pos exact-integer?] 
-                                     [phase (or/c 0 1)])) ; direct access to exported id
+                                     [phase exact-nonnegative-integer?]))
 
 ;; Syntax object
 (define ((alist/c k? v?) l)