Bob Nystrom
14011f47e3
They're back from the grave, and ready to party! Change-Id: I088134a9be7ecabf1fbf751c015a656a15cabff9 Reviewed-on: https://dart-review.googlesource.com/12821 Commit-Queue: Bob Nystrom <rnystrom@google.com> Reviewed-by: William Hesse <whesse@google.com>
65 lines
2.5 KiB
Dart
65 lines
2.5 KiB
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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// Verify that '??' binds tighter than '?:' and less tightly than '||'.
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import "package:expect/expect.dart";
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assertionError(e) => e is AssertionError;
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// Determine whether the VM is running in checked mode.
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bool get checkedMode {
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try {
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var x = 'foo';
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int y = x;
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return false;
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} catch (_) {
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return true;
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}
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}
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main() {
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// Make sure the "none" test fails if "??" is not implemented. This makes
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// status files easier to maintain.
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var _ = null ?? null;
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// "a ?? b ?? c" should be legal, and should evaluate to the first non-null
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// value (or null if there are no non-null values).
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Expect.equals(1, 1 ?? 2 ?? 3); //# 01: ok
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Expect.equals(2, null ?? 2 ?? 3); //# 02: ok
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Expect.equals(3, null ?? null ?? 3); //# 03: ok
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Expect.equals(null, null ?? null ?? null); //# 04: ok
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// "a ?? b ? c : d" should parse as "(a ?? b) ? c : d", therefore provided
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// that a is true, b need not be a bool. An incorrect parse of
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// "a ?? (b ? c : d)" would require b to be a bool to avoid a static type
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// warning.
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Expect.equals(2, true ?? 1 ? 2 : 3); //# 05: ok
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// "a ?? b || c" should parse as "a ?? (b || c)", therefore it's a static
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// type warning if b doesn't have type bool. An incorrect parse of
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// "(a ?? b) || c" would allow b to have any type provided that a is bool.
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Expect.equals(false, false ?? 1 || true); //# 06: static type warning
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// "a || b ?? c" should parse as "(a || b) ?? c", therefore it is a static
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// type warning if b doesn't have type bool. An incorrect parse of
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// "a || (b ?? c)" would allow b to have any type provided that c is bool.
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if (checkedMode) {
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Expect.throws(() => false || 1 ?? true, assertionError); //# 07: static type warning
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} else {
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Expect.equals(false, false || 1 ?? true); // //# 07: continued
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}
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if (checkedMode) {
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// An incorrect parse of "a || (b ?? c)" would result in no checked-mode
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// error.
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Expect.throws(() => false || null ?? true, assertionError); //# 08: ok
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} else {
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// An incorrect parse of "a || (b ?? c)" would result in c being evaluated.
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int i = 0; // //# 08: continued
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Expect.equals(false, false || null ?? i++ == 0); // //# 08: continued
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Expect.equals(0, i); // //# 08: continued
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}
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}
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