private function removeUsedField(ASTNode $postfix)
{
$image = '$';
$child = $postfix->getFirstChildOfType('Identifier');
if ($postfix->getParent()->isStatic()) {
$image = '';
$child = $postfix->getFirstChildOfType('Variable');
}
if ($this->isValidPropertyNode($child)) {
unset($this->fields[$image . $child->getImage()]);
}
}