expander: fix problem with module->namespace and shifts

When expanding in a namespace for a module unmarshaled from ".zo"
form, a scope corresponding to the module's "inside edge" is added to
every expansion. Before this repair, the scope was detached from
module path index shifts that might apply to the bindings (including
references to bulk bindings). Repair the problem by adding suitable
shifts when adding the scope.

Thanks to William Hatch for the bug report.

racket/src/expander/expand/context.rkt

@@ -76,6 +76,7 @@
   (expand-context (root-expand-context-self-mpi root-ctx)
                   (root-expand-context-module-scopes root-ctx)
                   (root-expand-context-post-expansion-scope root-ctx)
+                  (root-expand-context-post-expansion-shifts root-ctx)
                   (root-expand-context-top-level-bind-scope root-ctx)
                   (root-expand-context-all-scopes-stx root-ctx)
                   (root-expand-context-use-site-scopes root-ctx)

racket/src/expander/expand/definition-context.rkt

@@ -260,6 +260,12 @@
                      (and same-kind?
                           (memq context '(module module-begin top-level))
                           (root-expand-context-post-expansion-scope ctx)))]
+                [post-expansion-shifts
+                 #:parent root-expand-context
+                 (if (and same-kind?
+                          (eq? context 'top-level))
+                     (root-expand-context-post-expansion-shifts ctx)
+                     null)]
                 [post-expansion-scope-action
                  (if (and intdefs (not (null? intdefs)))
                      (lambda (s placeholder-sc)

racket/src/expander/expand/main.rkt

@@ -463,9 +463,11 @@
     ;; if the macro expands to a definition form, the binding will be
     ;; in the definition context's scope. The sepcific action depends
     ;; on the expansion context.
-    ((expand-context-post-expansion-scope-action ctx)
-     s
-     (root-expand-context-post-expansion-scope ctx))]
+    (define new-s
+      ((expand-context-post-expansion-scope-action ctx)
+       s
+       (root-expand-context-post-expansion-scope ctx)))
+    (syntax-add-shifts new-s (root-expand-context-post-expansion-shifts ctx))]
    [else s]))
 
 (define (accumulate-def-ctx-scopes ctx def-ctx-scopes)

racket/src/expander/expand/root-expand-context.rkt

@@ -21,6 +21,7 @@
          (self-mpi        ; MPI for the enclosing module during compilation
           module-scopes   ; list of scopes for enclosing module or top level; includes next two fields
           * post-expansion-scope  ; #f or scope to add to every expansion; often module's inside edge
+          * post-expansion-shifts ; a list of MPIshifts to go with `post-expansion-scope`
           top-level-bind-scope  ; #f or a scope to constrain expansion bindings; see "expand-bind-top.rkt"
           all-scopes-stx  ; scopes like the initial import, which correspond to original forms
           * use-site-scopes ; #f or boxed list: scopes that should be pruned from binders
@@ -41,6 +42,7 @@
   (root-expand-context self-mpi
                        module-scopes
                        post-expansion-scope
+                       null ; post-expansion-shifts
                        (new-scope 'module) ; top-level-bind-scope
                        (or all-scopes-stx
                            (add-scopes empty-syntax module-scopes))
@@ -57,7 +59,8 @@
   (datum->syntax
    #f
    (vector (add-scopes empty-syntax (root-expand-context-module-scopes ctx))
-           (add-scope empty-syntax (root-expand-context-post-expansion-scope ctx))
+           (syntax-add-shifts (add-scope empty-syntax (root-expand-context-post-expansion-scope ctx))
+                              (root-expand-context-post-expansion-shifts ctx))
            (syntax-module-path-index-shift (root-expand-context-all-scopes-stx ctx) orig-self new-self)
            (add-scopes empty-syntax (unbox (root-expand-context-use-site-scopes ctx)))
            (for/hasheqv ([(phase ht) (in-hash (root-expand-context-defined-syms ctx))]) ; make immutable
@@ -83,6 +86,7 @@
   (root-expand-context self
                        (extract-scope-list (vector-ref vec 0)) ; module-scopes
                        (extract-scope (vector-ref vec 1))      ; post-expansion-scope
+                       (extract-shifts (vector-ref vec 1))     ; post-expansion-scope-shifts
                        (new-scope 'module)                     ; top-level-bind-scope
                        (vector-ref vec 2)                      ; all-scopes-stx
                        (box (extract-scope-list (vector-ref vec 3))) ; use-site-scopes
@@ -110,6 +114,9 @@
   (define s (syntax-scope-set stx 0))
   (generalize-scope (set-first s)))
 
+(define (extract-shifts stx)
+  (syntax-mpi-shifts stx))
+
 (define (unpack-defined-syms v)
   (hash-copy ; make mutable
    (for/hasheqv ([(phase ht-s) (in-hash (syntax-e v))])

racket/src/expander/syntax/binding.rkt

@@ -37,6 +37,7 @@
  syntax-apply-shifts
  binding-module-path-index-shift
  syntax-transfer-shifts
+ syntax-add-shifts
  
  syntax-source-module
  identifier-prune-to-source-module)
@@ -280,7 +281,9 @@
    [else b]))
 
 (define (syntax-transfer-shifts to-s from-s [inspector #f] #:non-source? [non-source? #f])
-  (define shifts (syntax-mpi-shifts from-s))
+  (syntax-add-shifts to-s (syntax-mpi-shifts from-s) inspector #:non-source? non-source?))
+
+(define (syntax-add-shifts to-s shifts [inspector #f] #:non-source? [non-source? #f])
   (cond
    [(and (null? shifts) inspector)
     (syntax-set-inspector to-s inspector)]