in src/core/Node.hack [777:792]
final public function __getChildrenDescription(): string {
$desc = varray[];
foreach ($this->children as $child) {
if ($child is node) {
$tmp = '\\'.\get_class($child);
$categories = $child->__xhpCategoryDeclaration();
if (C\count($categories) > 0) {
$tmp .= '[%'.Str\join(Vec\keys($categories), ',%').']';
}
$desc[] = $tmp;
} else {
$desc[] = 'pcdata';
}
}
return Str\join($desc, ',');
}