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cc736dfb65
This reapplies commit0c05e33836and reverts the revert029e0cec71. Tested: Added few new tests, updated existing. Mainly regression testing. CoreLibraryReviewExempt: Reviewed in original CL. Change-Id: Ifcc79ce2f9375f607722643a04957b0961e6c295 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/284304 Reviewed-by: Ömer Ağacan <omersa@google.com> Commit-Queue: Lasse Nielsen <lrn@google.com> Reviewed-by: Aske Simon Christensen <askesc@google.com> Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
34 lines
1.1 KiB
Dart
34 lines
1.1 KiB
Dart
// Copyright (c) 2013, 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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part of dart.core;
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/// The reserved word `null` denotes an object that is the sole instance of
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/// this class.
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///
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/// The `Null` class is the only class which does not implement `Object`.
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/// It is a compile-time error for a class to attempt to extend or implement
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/// [Null].
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///
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/// The language contains a number of specialized operators for working with
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/// `null` value. Examples:
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/// ```dart
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/// e1! // Throws if e1 is null.
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/// e2 ?? e3 // Same as e2, unless e2 is null, then use value of e3
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/// x ??= e4 // Same as x unless x is null, then same as `x = e4`.
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/// e5?.foo() // call `foo` on e5, unless e5 is null.
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/// [...? e6] // spreads e6 into the list literal, unless e6 is null.
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/// ```
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@pragma("vm:entry-point")
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final class Null {
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factory Null._uninstantiable() {
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throw UnsupportedError('class Null cannot be instantiated');
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}
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external int get hashCode;
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/// Returns the string `"null"`.
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String toString() => "null";
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}
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