add empty? to the list of known-good-contracts

racket/collects/racket/contract/private/helpers.rkt

@@ -13,7 +13,9 @@
 
 (require setup/main-collects
          racket/struct-info
-         (for-template racket/base))
+         (only-in racket/private/list empty?)
+         (for-template racket/base
+                       (only-in racket/private/list empty?)))
 
 (define (update-loc stx loc)
   (datum->syntax stx (syntax-e stx) loc))
@@ -189,6 +191,8 @@
              string<=?
              #:key symbol->string)))
 
+-- also add empty? to the above
+
 |#
 
 (define known-good-syms-ht 
@@ -365,7 +369,9 @@
          (void? . #t)
          (weak-box? . #t)
          (will-executor? . #t)
-         (zero? . #t)))
+         (zero? . #t)
+         ;; from racket/private/list
+         (empty? . #t)))
 
 (define (known-good-contract? id)
   (define r-id (syntax-e id))

racket/collects/racket/list.rkt

@@ -61,7 +61,8 @@
          remf
          remf*)
 
-(require (for-syntax racket/base))
+(require (for-syntax racket/base)
+         (only-in racket/private/list empty?))
 
 (define (first x)
   (if (and (pair? x) (list? x))
@@ -112,7 +113,6 @@
     (raise-argument-error 'rest "(and/c list? (not/c empty?))" l)))
 
 (define (cons? l) (pair? l))
-(define (empty? l) (null? l))
 (define empty '())
 
 (define (make-list n x)

racket/collects/racket/private/list.rkt

@@ -30,7 +30,11 @@
            reverse
 
            compose
-           compose1)
+           compose1
+
+           empty?)
+
+  (define (empty? l) (null? l))
 
   (#%require (rename "sort.rkt" raw-sort sort)
              (for-syntax "stxcase-scheme.rkt")