bug#22447: (rnrs hashtables): Mutation of immutable hashtable ignored

[Taylan Ulrich Bayırlı/Kammer]

Sorry about the duplicate bug report; I merged it into this one.

Here's the patch again.  (Merged report seemed invisible in the web
interface.)

>From dd6c4bbbe85a57fcbb08bdc7847075bddc1f0d87 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Taylan=20Ulrich=20Bay=C4=B1rl=C4=B1/Kammer?=
 <address@hidden>
Date: Sat, 23 Jan 2016 22:35:24 +0100
Subject: [PATCH] Hashtable-set! errors on immutable hashtable.

* module/rnrs/hashtables.scm (hashtable-set!): Raise an assertion
  violation error when the hashtable is immutable.
---
 module/rnrs/hashtables.scm | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/module/rnrs/hashtables.scm b/module/rnrs/hashtables.scm
index 98d2d76..5773eb1 100644
--- a/module/rnrs/hashtables.scm
+++ b/module/rnrs/hashtables.scm
@@ -122,8 +122,9 @@
 
   (define (hashtable-set! hashtable key obj)
     (if (r6rs:hashtable-mutable? hashtable)
-       (hash-table-set! (r6rs:hashtable-wrapped-table hashtable) key obj))
-    *unspecified*)
+        (hash-table-set! (r6rs:hashtable-wrapped-table hashtable) key obj)
+        (assertion-violation
+         'hashtable-set! "Hashtable is immutable." hashtable)))
 
   (define (hashtable-delete! hashtable key)
     (if (r6rs:hashtable-mutable? hashtable)
-- 
2.6.3