Avoid use of void so much

implementations/racket/preserves/preserves-schema/compiler.rkt

@@ -94,6 +94,8 @@
              (cons (struct-stx (list name variant-name) '()) acc)]
             [_
              (cons (struct-stx (list name variant-name) '(value)) acc)]))]
+       [(ty-unit)
+        (cons (struct-stx (list name) '()) acc)]
        [(ty-record fields)
         (cons (struct-stx (list name) (map car fields)) acc)]
        [_

implementations/racket/preserves/preserves-schema/gen/schema.rkt

@@ -74,6 +74,7 @@
         (SimplePattern-setof? p)
         (SimplePattern-dictof? p)
         (SimplePattern-Ref? p)))
+  (struct Version () #:prefab)
   (begin
     (define (parse-AtomKind input)
       (match
@@ -362,7 +363,7 @@
       (parse-success-or-error 'parse-SimplePattern parse-SimplePattern)))
   (begin
     (define (parse-Version input)
-      (match input ((and dest (== '1)) (void)) (_ eof)))
+      (match input ((and dest (== '1)) (Version)) (_ eof)))
     (define parse-Version!
       (parse-success-or-error 'parse-Version parse-Version)))
   (define (AtomKind->preserves input)
@@ -519,4 +520,4 @@
         (SimplePattern->preserves $key)
         (SimplePattern->preserves $value))))
      ((SimplePattern-Ref src) (Ref->preserves src))))
-  (define (Version->preserves input) (match input ((? void?) '1))))
+  (define (Version->preserves input) (match input ((Version) '1))))

implementations/racket/preserves/preserves-schema/parser.rkt

@@ -41,7 +41,7 @@
 (define (construct name wrap? ty)
   (match ty
     [(ty-record fields) `(,name ,@(map escape (map car fields)))]
-    [(ty-unit) (if wrap? `(,name) `(void))]
+    [(ty-unit) `(,name)]
     [_ (if wrap? `(,name dest) 'dest)]))
 
 (define (maybe-dest dest-pat-stx pat)

implementations/racket/preserves/preserves-schema/unparser.rkt

@@ -40,7 +40,7 @@
 (define (deconstruct name wrap? ty)
   (match ty
     [(ty-record fields) `(,name ,@(map escape (map car fields)))]
-    [(ty-unit) (if wrap? `(,name) '(? void?))]
+    [(ty-unit) `(,name)]
     [_ (if wrap? `(,name src) 'src)]))
 
 (define (pattern->unparser pattern src-stx)