units: Fix an improper use of syntax instead of quote-syntax

pkgs/racket-test/tests/units/test-unit.rkt

@@ -2241,3 +2241,38 @@
   (test-runtime-error exn:fail:contract?
                       "make-foo: broke its own contract"
                       (dynamic-require ''use #f)))
+
+;; ----------------------------------------
+;; Ellipses in signature bodies should not cause problems due to syntax template misuse
+
+(parameterize ([current-namespace (make-base-namespace)])
+  (eval
+   '(module m racket/base
+      (require racket/contract
+               racket/unit)
+
+      (provide result)
+
+      (define-signature foo^
+        [(contracted [foo (-> integer? ... integer?)])])
+
+      (define-unit foo@
+        (import)
+        (export foo^)
+        (define (foo . xs) (apply + xs)))
+
+      (define (foo+1@ foo-base@)
+        (define-values/invoke-unit foo-base@
+          (import)
+          (export (prefix base: foo^)))
+        (unit
+          (import)
+          (export foo^)
+          (define (foo . xs) (add1 (apply base:foo xs)))))
+
+      (define-values/invoke-unit (foo+1@ foo@)
+        (import)
+        (export foo^))
+
+      (define result (foo 1 2 3))))
+  (test 7 (dynamic-require ''m 'result)))

racket/collects/racket/private/unit-utils.rkt

@@ -46,13 +46,15 @@
             (syntax-case stx (set!)
               [x
                (identifier? #'x)
-               #'#,(add-ctc i (bound-identifier-mapping-get
+               (quote-syntax
+                #,(add-ctc i (bound-identifier-mapping-get
                               member-table
-                               i))]
+                              i)))]
               [(x . y)
-               #'(#,(add-ctc i (bound-identifier-mapping-get
+               (quote-syntax
+                (#,(add-ctc i (bound-identifier-mapping-get
                                member-table
-                                i)) . y)])))])))
+                               i)) . y))])))])))
 
 (define-syntax (unit-export stx)
   (syntax-case stx ()