make bindings "pass" implementation mirror the others

It's useful to think of each pass as applying some core transformation
using some strategy. In this case, the transformation is the bindings
rewrite rule, and the strategy is to traverse the syntax in applying
it.

qi-lib/flow/core/compiler/2000-bindings.rkt

@@ -38,13 +38,12 @@
 
   ;; (as name) → (~> (esc (λ (x) (set! name x))) ⏚)
   ;; TODO: use a box instead of set!
-  (define (rewrite-all-bindings stx)
-    (find-and-map/qi (syntax-parser
-                       [((~datum as) x ...)
-                        #:with (x-val ...) (generate-temporaries (attribute x))
-                        #'(thread (esc (λ (x-val ...) (set! x x-val) ...)) ground)]
-                       [_ this-syntax])
-                     stx))
+  (define rewrite-binding
+    (syntax-parser
+      [((~datum as) x ...)
+       #:with (x-val ...) (generate-temporaries (attribute x))
+       #'(thread (esc (λ (x-val ...) (set! x x-val) ...)) ground)]
+      [_ this-syntax]))
 
   (define (bound-identifiers stx)
     (let ([ids null])
@@ -68,6 +67,5 @@
     ;; TODO: use syntax-parse and match ~> specifically.
     ;; Since macros are expanded "outside in," presumably
     ;; it will naturally wrap the outermost ~>
-    (wrap-with-scopes (rewrite-all-bindings stx)
+    (wrap-with-scopes (find-and-map/qi rewrite-binding stx)
                       (bound-identifiers stx))))
-