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b101a7d002
Change-Id: Ib33169c3e0ffc870915c189404074a1dea472546 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/196548 Reviewed-by: Bob Nystrom <rnystrom@google.com> Commit-Queue: Leaf Petersen <leafp@google.com>
71 lines
2.5 KiB
Dart
71 lines
2.5 KiB
Dart
// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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// @dart = 2.9
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import "dart:collection";
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import "package:expect/expect.dart";
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import 'cast_helper.dart';
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void main() {
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testDowncastDirectAccess();
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testDowncastNoDirectAccess();
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testDowncastUntouchableElements();
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testUpcast();
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}
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void testDowncastDirectAccess() {
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var iterable = new Iterable<C>.generate(elements.length, (n) => elements[n]);
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// An iterable that (likely) can do direct access.
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var dIterable = Iterable.castFrom<C, D>(iterable);
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Expect.throws(() => dIterable.first, null, "direct.first");
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Expect.equals(d, dIterable.elementAt(1));
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Expect.throws(() => dIterable.elementAt(2), null, "direct.2"); // E is not D.
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Expect.equals(f, dIterable.skip(3).first); // Skip does not access element.
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Expect.equals(null, dIterable.skip(3).elementAt(1));
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Expect.throws(() => dIterable.toList(), null, "direct.toList");
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}
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void testDowncastNoDirectAccess() {
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var iterable = new Iterable<C>.generate(elements.length, (n) => elements[n]);
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// An iterable that cannot do direct access.
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var dIterable = Iterable.castFrom<C, D>(iterable.where((_) => true));
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Expect.throws(() => dIterable.first, null, "nonDirect.first");
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Expect.equals(d, dIterable.elementAt(1));
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// E is not D.
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Expect.throws(() => dIterable.elementAt(2), null, "nonDirect.2");
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Expect.equals(f, dIterable.skip(3).first); // Skip does not access element.
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Expect.equals(null, dIterable.skip(3).elementAt(1));
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Expect.throws(() => dIterable.toList(), null, "nonDirect.toList");
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}
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void testDowncastUntouchableElements() {
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// Iterable that definitely won't survive accessing element 3.
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var iterable = new Iterable<C>.generate(
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elements.length, (n) => n == 3 ? throw "untouchable" : elements[n]);
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var dIterable = Iterable.castFrom<C, D>(iterable);
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Expect.throws(() => dIterable.first, null, "untouchable.first");
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Expect.equals(d, dIterable.elementAt(1));
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Expect.throws(() => dIterable.elementAt(3), null, "untouchable.3");
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// Skip does not access element.
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Expect.equals(null, dIterable.skip(4).first);
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Expect.equals(null, dIterable.skip(3).elementAt(1));
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Expect.throws(() => dIterable.toList(), null, "untouchable.toList");
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}
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void testUpcast() {
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var iterable = new Iterable<C>.generate(elements.length, (n) => elements[n]);
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var objectIterable = Iterable.castFrom<C, Object>(iterable);
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Expect.listEquals(elements, objectIterable.toList());
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}
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