// Copyright (c) 2016, 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.md file.
// @dart=2.9
class A {
  operator +(String s) => null;

  operator [](i) => null;

  operator []=(i, val) {}
}

class B extends A {
  operator +(String s) => super + ("${s}${s}");

  operator [](i) => super[i];

  operator []=(i, val) => super[i++] += val;
}

class Autobianchi {
  g() => super[0];
}