From 09b3b2fb3c8883b300eb1e908010013b27791f5d Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Sat, 19 Jan 2019 08:49:23 -0700
Subject: [PATCH] io: fix `file-stream?` to always return a boolean

---
 racket/src/io/port/file-stream.rkt | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/racket/src/io/port/file-stream.rkt b/racket/src/io/port/file-stream.rkt
index 337e3886aa..107382b160 100644
--- a/racket/src/io/port/file-stream.rkt
+++ b/racket/src/io/port/file-stream.rkt
@@ -12,13 +12,14 @@
   (make-struct-type-property 'file-stream))
 
 (define (file-stream-port? p)
-  (file-stream-ref
-   (core-port-data
-    (cond
-      [(input-port? p) (->core-input-port p)]
-      [(output-port? p) (->core-output-port p)]
-      [else
-       (raise-argument-error 'file-stream-port?
-                             "port?"
-                             p)]))
-   #f))
+  (and (file-stream-ref
+        (core-port-data
+         (cond
+           [(input-port? p) (->core-input-port p)]
+           [(output-port? p) (->core-output-port p)]
+           [else
+            (raise-argument-error 'file-stream-port?
+                                  "port?"
+                                  p)]))
+        #f)
+       #t))