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

abstract class A<X extends core::Object? = dynamic> extends core::Object {
  synthetic constructor •() → self::A<self::A::X%>
    ;
  method foo<covariant-by-class Y extends self::A::X%>() → void
    ;
}
class B<Z extends core::Object? = dynamic> extends self::A<self::B::Z%> {
  synthetic constructor •() → self::B<self::B::Z%>
    ;
}
static method main() → void
  ;