pkg/front_end/testcases/nnbd/issue_39286_2.dart

// Copyright (c) 2019, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

class C {
  int y;
  D? f() => new D();
  C h() => this;
}
class D {
  D g() => this;
  String operator [](String s) { return "!$s!";}
}
void test(C x) {
  x..f()!.g()['Hi!']!..h()!.y = 2;
}
main() {
  test(new C());
}