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%>
    : super core::Object::•()
    ;
  abstract method foo({covariant-by-class core::Iterable<self::A::X%>? x = #C1}) → void;
}
class B<Y extends core::Object? = dynamic> extends core::Object implements self::A<self::B::Y%> {
  synthetic constructor •() → self::B<self::B::Y%>
    : super core::Object::•()
    ;
  method foo({covariant-by-class core::Iterable<self::B::Y%>? x = #C1}) → void {}
}
static method main() → dynamic {}

constants  {
  #C1 = null
}