LibTest/collection/IterableMixin/where_A02_t01.dart

// Copyright (c) 2017, 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.

// @dart = 2.9

/// @assertion Iterable<E> where(bool f(E element))
/// As long as the returned [Iterable] is not iterated over, the supplied
/// function [test] will not be invoked.
/// @description Checks that filtering happens lazily.
/// @author iarkh@unipro.ru


import "dart:collection";
import "../../../Utils/expect.dart";

class MyIterable<int> extends Object with IterableMixin {
  List _content;
  MyIterable(List list): _content = list;

  Iterator get iterator {
    return _content.iterator;
  }
}

bool test(var value) {
  Expect.fail("test($value) called");
  return true;
}

main() {
  new MyIterable([1, 2, -3, 4]).where(test);
  new MyIterable([]).where(test);
  new MyIterable(const[null, 2, -5, -6, 100]).where(test);
}