Fix up singleton values

original commit: d0939ffa1e57894a076bfd6326c4d977cfdf3e2e

collects/typed-scheme/private/type-utils.ss

@@ -56,6 +56,12 @@
                                  (make-ValuesDots (map sb types) (sb dty) dbound))])
       target))
 
+;; the other definition is not accessible here
+(define (-values args)
+  (if (= (length args) 1)
+      (car args)
+      (make-Values args)))
+
 ;; substitute-dots : Listof[Type] Option[type] Name Type -> Type
 (define (substitute-dots images rimage name target)    
   (define (sb t) (substitute-dots images rimage name t))
@@ -63,7 +69,7 @@
       (type-case sb target
                  [#:ValuesDots types dty dbound
                                (if (eq? name dbound)
-                                   (make-Values
+                                   (-values
                                     (append 
                                      (map sb types)
                                      ;; We need to recur first, just to expand out any dotted usages of this.