It's pretty understandable that the word class is a reserved word in JavaScript and so it's not a good idea to use that word as a name of variable. As for keys/identifiers (such as model/record field names), it has never been a problem. Until ExtJS 4.1.
So, the following code
Ext.define('Foo', {
    extend: '',
    fields: ['class']
generates a "class is a reserved identifier" error on Firefox 9.0.1):


For some reason, field identifiers get evaluated to variables.
So, the question is: do I have to go through my code and replace all "class" fields with "cls", or is this behaviour unintentional and will be fixed?