struct: disallow #:extra-name with #:omit-define-syntaxes

pkgs/racket-doc/scribblings/reference/define-struct.scrbl

@@ -180,7 +180,8 @@ If @racket[name-id] is supplied via @racket[#:extra-name] and it is
 not @racket[id], then both @racket[name-id] and @racket[id] are bound
 to information about the structure type. Only one of
 @racket[#:extra-name] and @racket[#:name] can be provided within a
-@racket[struct] form.
+@racket[struct] form, and @racket[#:extra-name] cannot be combined
+with @racket[#:omit-define-syntaxes].
 
 @examples[#:eval posn-eval
   (struct ghost (color name) #:prefab #:extra-name GHOST)

pkgs/racket-test-core/tests/racket/struct.rktl

@@ -1193,6 +1193,9 @@
 (test 'blinky ghost-name (struct-copy GHOST (ghost 'red 'blinky)))
 (syntax-test #'GHOST)
 
+(syntax-test #'(struct ghost (color name) #:extra-name GHOST #:omit-define-syntaxes)
+             "cannot be combined")
+
 ;; ----------------------------------------
 ;; Check `#:authentic`:
 

racket/collects/racket/private/define-struct.rkt

@@ -741,6 +741,8 @@
                           (lambda ()
                             (cond
                               [(and info-name (not name-only?))
+                               (when omit-define-syntaxes?
+                                 (raise-syntax-error #f "#:extra-name cannot be combined with #:omit-define-syntaxes" stx))
                                ; reuse existing value
                                (list #`(define-syntaxes (#,info-name) (syntax-local-value #'#,id)))]
                               [else null]))])