Paul Berry
e933e91aaa
This is a reland of 6a1c54ec30
Original change's description:
> Flow analysis: promote to non-nullable on initialization
>
> When flow analysis encounters a variable declaration of the form `T? x
> = expr;`, if the type of `expr` is `T`, then the variable is
> immediately promoted to type `T`.
>
> Fixes #43099.
>
> Change-Id: Ia206fe0d50e2fdd9bdf637e13c85633d8490dbcc
> Bug: https://github.com/dart-lang/sdk/issues/43099
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/163841
> Commit-Queue: Paul Berry <paulberry@google.com>
> Reviewed-by: Bob Nystrom <rnystrom@google.com>
> Reviewed-by: Johnni Winther <johnniwinther@google.com>
> Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Bug: https://github.com/dart-lang/sdk/issues/43099
Change-Id: I7530bb0f7c24674a7b500558b89d50b35e045aca
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/166305
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
34 lines
785 B
Dart
34 lines
785 B
Dart
// Copyright (c) 2015, 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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// Evaluation of an if-null expression e of the form e1 ?? e2 is equivalent to
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// the evaluation of the expression ((x) => x == null ? e2 : x)(e1).
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//
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// Therefore, e1 should be evaluated first; if it is non-null, e2 should not
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// be evaluated.
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import "package:expect/expect.dart";
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bad() {
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throw new Exception();
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}
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bool firstExecuted = false;
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first() {
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firstExecuted = true;
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return null;
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}
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second() {
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Expect.isTrue(firstExecuted);
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return 2;
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}
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main() {
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var one = 1 as int?;
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Expect.equals(1, one ?? bad());
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Expect.equals(2, first() ?? second());
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}
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