Add #:unless to the for: macros.

collects/tests/typed-racket/succeed/for.rkt

@@ -37,6 +37,13 @@
                    #:when (odd? i))
                   (+ i j 10))
        '(21 43))
+(check equal?
+       (for/list: : (Listof Integer)
+                  ((i : Integer '(1 2 3))
+                   (j : Integer '(10 20 30))
+                   #:unless (odd? i))
+                  (+ i j 10))
+       '(32))
 
 (check equal?
        (for/or: : Boolean
@@ -113,6 +120,15 @@
                     (k : Integer '(100 200 300)))
                    (+ acc i j k))
        1998)
+(check =
+       (for*/fold: : Integer
+                   ((acc : Integer 0))
+                   ((i : Integer '(1 2 3))
+                    #:unless (even? i)
+                    (j : Integer '(10 20 30))
+                    (k : Integer '(100 200 300)))
+                   (+ acc i j k))
+       3996)
 
 (check =
        (for/sum: : Integer

collects/typed-racket/base-env/for-clauses.rkt

@@ -21,7 +21,9 @@
                                          ((v.ann-name ...) seq-expr))))
     ;; when clause
     (pattern (~seq #:when guard:expr)
-             #:with (expand ...) (list #'#:when #'guard)))
+             #:with (expand ...) (list #'#:when #'guard))
+    (pattern (~seq #:unless guard:expr)
+             #:with (expand ...) (list #'#:unless #'guard)))
 
 ;; intersperses "#:when #t" clauses to emulate the for* variants' semantics
 (define-splicing-syntax-class for*-clause
@@ -40,4 +42,6 @@
                                        #'#:when #'#t))
     ;; when clause
     (pattern (~seq #:when guard:expr)
-             #:with (expand ...) (list #'#:when #'guard)))
+             #:with (expand ...) (list #'#:when #'guard))
+    (pattern (~seq #:unless guard:expr)
+             #:with (expand ...) (list #'#:unless #'guard)))