From 7eb1ef925035296b397ada1435a46453310943a2 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Sat, 23 Nov 2019 15:25:34 -0500
Subject: [PATCH] cs: fix printing on struct type with custom write

Don't try to use a struct type's custom-write procedure on the struct
type itself.

Relevant to #2926
---
 pkgs/racket-test-core/tests/racket/struct.rktl | 2 ++
 racket/src/io/print/graph.rkt                  | 6 ++++--
 racket/src/io/print/main.rkt                   | 4 +++-
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/pkgs/racket-test-core/tests/racket/struct.rktl b/pkgs/racket-test-core/tests/racket/struct.rktl
index fe45e24beb..0b08a6002c 100644
--- a/pkgs/racket-test-core/tests/racket/struct.rktl
+++ b/pkgs/racket-test-core/tests/racket/struct.rktl
@@ -867,6 +867,8 @@
   (define-values (s:tuple make-tuple tuple? tuple-ref tuple-set!)
     (make-struct-type 'tuple #f 1 0 #f
 		      (list (cons prop:custom-write tuple-print))))
+
+  (test "#<struct-type:tuple>" values (format "~s" s:tuple)) ; shouldn't trigger custom write
   
   (define (with-output-string thunk)
     (let ([p (open-output-string)])
diff --git a/racket/src/io/print/graph.rkt b/racket/src/io/print/graph.rkt
index 534d1cb079..6b251da3fe 100644
--- a/racket/src/io/print/graph.rkt
+++ b/racket/src/io/print/graph.rkt
@@ -53,7 +53,8 @@
        (and (not print-graph?)
             (not (eq? mode PRINT-MODE/UNQUOTED))
             (quick-no-graph? (mcdr v) (quick-no-graph? (mcar v) (sub1 fuel))))]
-      [(custom-write? v)
+      [(and (custom-write? v)
+            (not (struct-type? v)))
        #f]
       [(and (struct? v)
             (config-get config print-struct))
@@ -163,7 +164,8 @@
        (build-graph (mcar v) mode)
        (build-graph (mcdr v) mode)
        (done! v (eq? mode PRINT-MODE/UNQUOTED))]
-      [(custom-write? v)
+      [(and (custom-write? v)
+            (not (struct-type? v)))
        (define print-quotable (if (eq? mode PRINT-MODE/UNQUOTED)
                                   (custom-print-quotable-accessor v 'self)
                                   'self))
diff --git a/racket/src/io/print/main.rkt b/racket/src/io/print/main.rkt
index 29f3cffebe..7a33fc9679 100644
--- a/racket/src/io/print/main.rkt
+++ b/racket/src/io/print/main.rkt
@@ -200,6 +200,7 @@
               (hash? v)
               (prefab-struct-key v)
               (and (custom-write? v)
+                   (not (struct-type? v))
                    (not (printable-regexp? v))
                    (not (eq? 'self (custom-print-quotable-accessor v 'self))))))
      ;; Since this value is not marked for constructor mode,
@@ -292,7 +293,8 @@
      (fail-unreadable who v)]
     [(mpair? v)
      (print-mlist p who v mode o max-length graph config)]
-    [(custom-write? v)
+    [(and (not (struct-type? v))
+          (custom-write? v))
      (let ([o/m (make-output-port/max o max-length)])
        (set-port-handlers-to-recur!
         o/m