in src/html/tags/r/Ruby.hack [19:31]
protected static function getChildrenDeclaration(): XHPChild\Constraint {
return XHPChild\any_of(
XHPChild\at_least_one_of(
XHPChild\any_of(XHPChild\pcdata(), XHPChild\of_type<rb>()),
),
XHPChild\at_least_one_of(XHPChild\any_of(
XHPChild\sequence(XHPChild\of_type<rp>(), XHPChild\of_type<rt>()),
XHPChild\sequence(XHPChild\of_type<rp>(), XHPChild\of_type<rtc>()),
XHPChild\sequence(XHPChild\of_type<rt>(), XHPChild\of_type<rp>()),
XHPChild\sequence(XHPChild\of_type<rtc>(), XHPChild\of_type<rp>()),
)),
);
}