http://dev.clojure.org/jira This file is an XML representation of an issue en-us 4.4 649 25-07-2011 http://dev.clojure.org/jira/browse/CLJ-1023 Clojure <p>The <tt>:unsynchronized-mutable</tt> fields of a <tt>deftype</tt> cannot be <tt>set!</tt> inside a <tt>try</tt> block that is not in tail position of the method.</p> <p>See file *<b>demonstration.clj</b>* for an complete code example.</p> CLJ-1023

non-tail-position try block breaks mutable fields in deftype

Defect Minor Closed Declined Rich Hickey Stuart Sierra Sun, 8 Jul 2012 16:20:25 -0500 Mon, 3 Dec 2012 10:55:08 -0600 Mon, 3 Dec 2012 10:55:08 -0600 Release 1.3 Release 1.4 0 1 <p>I looked at this. The problem is that non-tail try blocks turn into closures, and thus the field gets propagated as a constant. IOW this can't work:</p> <div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent"> <pre class="code-java">(deftype Foo4 [^:unsynchronized-mutable x] MutableX (set-x [<span class="code-keyword">this</span> v] ((fn [] (set! x v))) v))</pre> </div></div> <p>I'm not going to re-evaluate the try/closure approach right now, so I recommend you make a helper method that just does the assignment and then call that in the bigger context, as a workaround.</p> <p>Closing this as it requires more than a simple bug fix. If you feel that Rich's work-around is unsatisfactory please create a clojure-dev discussion about rewriting try-catch.</p> Global Rank