Handle rename transformers better in match expanders.

Closes PR 15223.

Merge to 6.4.

pkgs/racket-test/tests/match/examples.rkt

@@ -810,4 +810,21 @@
         [_ 'no])
       'yes))
 
+   (test-case "match-expander rename transformer"
+           (define-match-expander foo
+             (lambda (stx) (syntax-case stx () [(_ a) #'a]))
+             (make-rename-transformer #'values))
+
+           (check-equal? (foo 2) 2))
+
+   (test-case "match-expander rename transformer set!"
+              (define x 1)
+              (define-match-expander foo
+                (lambda (stx) (syntax-case stx () [(_ a) #'a]))
+                (make-rename-transformer #'x))
+
+              (set! foo 2)
+              (check-equal? x 2))
+
+
 ))

racket/collects/racket/match/match-expander.rkt

@@ -11,12 +11,29 @@
         #:property prop:set!-transformer 
         (λ (me stx)
           (define xf (match-expander-macro-xform me))
-          (if (set!-transformer? xf)
+          (define proc
-              ((set!-transformer-procedure xf) stx)
+            (cond [(rename-transformer? xf)
+                   (lambda (x)
+                     (define target (rename-transformer-target xf))
+                     (syntax-case stx (set!)
+                       [(set! id args ...)
+                        #`(set! #,target args ...)]
+                       [(id args ...)
+                        (datum->syntax stx
+                                       `(,target ,@(syntax->list #'(args ...)))
+                                       stx stx)]
+                       [_ (rename-transformer-target xf)]))]
+                  [(set!-transformer? xf) (set!-transformer-procedure xf)]
+                  [(procedure? xf)
+                   (lambda (stx)
                      (syntax-case stx (set!)
                        [(set! . _)
                         (raise-syntax-error #f "cannot mutate syntax identifier" stx)]
-                [_ (xf stx)])))
+                       [_ (xf stx)]))]
+                  [else (raise-syntax-error
+                         #f
+                         "not a procedure for match expander transformer" stx)]))
+          (proc stx))
           #:property prop:match-expander (struct-field-index match-xform)
         #:property prop:legacy-match-expander (struct-field-index legacy-xform))
       (values make-match-expander))))