library /*isNonNullableByDefault*/;
import self as self;
import "dart:core" as core;
import "dart:collection" as col;

class Element extends core::Object {
  synthetic constructor •() → self::Element
    : super core::Object::•()
    ;
}
class Class<E extends self::Element? = self::Element?> extends core::Object {
  generic-covariant-impl field self::Class::E? element;
  constructor •(self::Class::E? element) → self::Class<self::Class::E%>
    : self::Class::element = element, super core::Object::•()
    ;
  method setElement(generic-covariant-impl self::Class::E? element) → void {
    if(!this.{self::Class::element}.{core::Object::==}(element)) {
      this.{self::Class::element} = element;
      core::Set<self::Element> elements = col::LinkedHashSet::•<self::Element>();
      if(!element.{core::Object::==}(null)) {
        elements.{core::Set::add}(element{self::Class::E% & self::Element /* '%' & '!' = '!' */});
      }
      if(!this.{self::Class::element}.{core::Object::==}(null)) {
        elements.{core::Set::add}(this.{self::Class::element}!);
      }
    }
  }
}
static method main() → dynamic {}