rebirth: Add define/define-macro rest support

That is: `(define (foo bar . rest))'.

* build-aux/bootstrap/rebirth.scm (params->es): Add rest support.

build-aux/bootstrap/rebirth.scm

@@ -718,12 +718,30 @@
 
 ;; Compile parameter list.
 ;;
-;; This simply takes the value of the symbol and outputs it (formatted),
-;; delimited by commas.
+;; This takes the value of the symbol and outputs it (formatted), delimited
+;; by commas.
+;;
+;; Since we do not support actual pairs (yet), the "." syntax that normally
+;; denotes the cdr is retained and presents itself here.  The form "(arg1,
+;; arg2 . rest)" creates a list `rest' containing all remaining arguments
+;; after that point.  Conveniently, ECMAScript Harmony supports this
+;; natively with the "..." syntax.
 (define (params->es params)
-  (join ", " (map (lambda (t)
-                    (tname->id (token-value t)))
-                  params)))
+  (define (%param-conv params)
+    (let* ((param (car params))
+           (name  (token-value param))
+           (id    (tname->id name))
+           (rest  (cdr params)))
+      (if (string=? name ".")
+          (list (string-append
+                 "..." (car (%param-conv rest))))
+          (if (pair? rest)
+              (cons id (%param-conv rest))
+              (list id)))))
+
+  (if (pair? params)
+      (join "," (%param-conv params))
+      ""))
 
 
 ;; Compile body s-expressions into ECMAScript