dart-sdk/pkg/front_end/testcases/argument.dart

abstract class Base {}

class Foo extends Base {}

class Bar extends Base {}

class Baz extends Base {}

void foo(x) {}

void bar(x) {}

void foo_escaped(x) {}

void bar_escaped(x) {}

void escape(fn) {
  fn(new Baz());
}

main() {
  foo(new Foo());
  bar(new Bar());
  escape(foo_escaped);
  escape(bar_escaped);
}