adjust the hole structs a little bit to get better printing at the REPL

pkgs/redex/private/lang-struct.rkt

@@ -14,9 +14,16 @@
 (define-struct rhs (pattern) #:transparent)
 (define-values (the-hole the-not-hole hole?)
   (let ()
-    (define-struct hole (id)
+    (define-struct hole ()
       #:property prop:equal+hash (list (λ (x y recur) #t) (λ (v recur) 255) (λ (v recur) 65535))
       #:inspector #f)
-    (define the-hole (make-hole 'the-hole))
-    (define the-not-hole (make-hole 'the-not-hole))
-    (values the-hole the-not-hole hole?)))
+    (define-struct not-hole ()
+      #:property prop:equal+hash (list (λ (x y recur) #t) (λ (v recur) 254) (λ (v recur) 65534))
+      #:inspector #f)
+    (define the-hole (make-hole))
+    (define the-not-hole (make-not-hole))
+    (define -hole?
+      (let ([hole?
+             (λ (x) (or (hole? x) (not-hole? x)))])
+        hole?))
+    (values the-hole the-not-hole -hole?)))