fix getting port name for reader errors

Closes #1121

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

@@ -888,6 +888,24 @@
 
   (delete-file path))
 
+;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Check reader error-message formatting for a struct port
+
+(let ()
+  (define-struct wrapper (other port)
+    #:property prop:input-port 1)
+  (err/rt-test
+   (read (wrapper #f
+                  (make-input-port "wrapped"
+                                   (lambda (bstr)
+                                     (bytes-set! bstr 0 (char->integer #\)))
+                                     1)
+                                   (lambda (bstr d evt)
+                                     (bytes-set! bstr 0 (char->integer #\)))
+                                     1)
+                                   void)))
+   exn:fail:read?))
+
 ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 (report-errs)

racket/src/racket/include/scheme.h

@@ -1545,10 +1545,6 @@ struct Scheme_Output_Port
   struct Scheme_Input_Port *input_half;
 };
 
-#define SCHEME_INPORT_VAL(obj) (((Scheme_Input_Port *)(obj))->port_data)
-#define SCHEME_OUTPORT_VAL(obj) (((Scheme_Output_Port *)(obj))->port_data)
-#define SCHEME_IPORT_NAME(obj) (((Scheme_Input_Port *)obj)->name)
-
 #define SCHEME_SPECIAL (-2)
 #define SCHEME_UNLESS_READY (-3)
 

racket/src/racket/src/error.c

@@ -2175,7 +2175,7 @@ void scheme_read_err(Scheme_Object *port,
 
     if (port) {
       Scheme_Object *pn;
-      pn = SCHEME_IPORT_NAME(port);
+      pn = scheme_input_port_record(port)->name;
       if (SCHEME_PATHP(pn)) {
 	pn = scheme_remove_current_directory_prefix(pn);
 	fn = SCHEME_PATH_VAL(pn);