From 3743324273f592681947eca6949f4d22560eae9b Mon Sep 17 00:00:00 2001
From: Oscar Waddell <owaddell@beckman.com>
Date: Tue, 7 Nov 2023 05:44:43 -0500
Subject: [PATCH] fix port-bol? return type

---
 mats/6.ms | 9 +++++++++
 s/io.ss   | 2 +-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/mats/6.ms b/mats/6.ms
index 041fed618..8fef13bbd 100644
--- a/mats/6.ms
+++ b/mats/6.ms
@@ -713,6 +713,15 @@
   (call-with-input-file "testfile.ss"
     (lambda (p)
       (string=? (get-string-all p) "a\n\nbc\n")))
+  (let ([op (open-output-string)])
+    ;; disguise boolean? check just enough to prevent cp0 from folding
+    ;; based on the declared return type; we need to actually check it
+    (define (check) (assert (memq (port-bol? op) '(#t #f))) #t)
+    (check)
+    (fprintf op "okay\n")
+    (check)
+    (write-char #\x op)
+    (check))
  )
 
 (mat char-ready?
diff --git a/s/io.ss b/s/io.ss
index 3af87d589..63a5e4085 100644
--- a/s/io.ss
+++ b/s/io.ss
@@ -214,7 +214,7 @@ implementation notes:
 
   (define eol-char?
     (lambda (c)
-      (memv c '(#\newline #\return #\nel #\ls))))
+      (and (memv c '(#\newline #\return #\nel #\ls)) #t)))
 
   (define-syntax port-gz-mode
     (syntax-rules ()