library test;

import 'dart:async';

T f<T>() => null;

class B<T> {
  D<T> g(E<T> x) => null;
}

class C<U> extends B<Future<U>> {
  E<Future<U>> g(Object x) => null;
  void h() {}
}

class D<T> {}

class E<T> extends D<T> {}

main() {}