(rnrs hashtables): Mutation of immutable hashtable ignored

Pinging this thread with a (very slightly) updated patch. :-)

[2. text/x-diff; 0001-Hashtable-set-errors-on-immutable-hashtable.patch]

From 7f35d515d711e255bba5a89a013d9d92034edf41 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Taylan=20Ulrich=20Bay=C4=B1rl=C4=B1/Kammer?=
 <taylanbayirli@gmail.com>
Date: Tue, 21 Jun 2016 00:25:19 +0200
Subject: [PATCH] Hashtable-set! errors on immutable hashtable.

* module/rnrs/hashtables.scm (hashtable-set!): Raise an assertion
  violation error when the hashtable is immutable.
* test-suite/tests/r6rs-hashtables.test: Fix accordingly.

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)

test-suite/tests/r6rs-hashtables.test

@@ -20,6 +20,7 @@
 (define-module (test-suite test-rnrs-hashtable)
   :use-module (ice-9 receive)
   :use-module ((rnrs hashtables) :version (6))
+  :use-module ((rnrs exceptions) :version (6))
   :use-module (srfi srfi-1)
   :use-module (test-suite lib))
 
@@ -130,8 +131,9 @@
 
   (pass-if "hashtable-copy with mutability #f produces immutable copy"
     (let ((copied-table (hashtable-copy (make-eq-hashtable) #f)))
-      (hashtable-set! copied-table 'foo 1)
-      (not (hashtable-ref copied-table 'foo #f)))))      
+      (guard (exc (else #t))
+        (hashtable-set! copied-table 'foo 1)
+        #f))))
 
 (with-test-prefix "hashtable-clear!"
   (pass-if "hashtable-clear! removes all values from hashtable"