recover from pattern errors caused by pos-fields

git-svn-id: http://haxe.googlecode.com/svn/trunk@6134 f16182fa-f095-11de-8f43-4547254af6c6
it's not

git-svn-id: http://haxe.googlecode.com/svn/trunk@6135 f16182fa-f095-11de-8f43-4547254af6c6