Adding Groovy / Grails Expression

If you have you have a groovy expression in your haml file like this:
%g:if{:test=>'${a!=null && b > c }'}
you get this:
<g:if test="${a!=null &amp;&amp; b > c}">....




and is doesn't work ... :( 

I add a new method to the AttributeValue model "isGroovyExpression"