Robert Nystrom
fc1b1ecc71
Change-Id: Idbcc965a27e9ffeedf5e0a1068b019de4193070f Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/127745 Commit-Queue: Bob Nystrom <rnystrom@google.com> Reviewed-by: Alexander Thomas <athom@google.com>
52 lines
1.7 KiB
Dart
52 lines
1.7 KiB
Dart
// Copyright (c) 2015, 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.
|
|
|
|
// Evaluation of an if-null expression e of the form e1 ?? e2 is equivalent to
|
|
// the evaluation of the expression ((x) => x == null ? e2 : x)(e1). The
|
|
// static type of e is the least upper bound of the static type of e1 and the
|
|
// static type of e2.
|
|
|
|
import "package:expect/expect.dart";
|
|
|
|
class A {
|
|
final String a;
|
|
A(this.a);
|
|
}
|
|
|
|
class B extends A {
|
|
B(String v)
|
|
: b = v,
|
|
super(v);
|
|
final String b;
|
|
}
|
|
|
|
class C extends A {
|
|
C(String v)
|
|
: c = v,
|
|
super(v);
|
|
final String c;
|
|
}
|
|
|
|
B nullB() => null;
|
|
C nullC() => null;
|
|
|
|
main() {
|
|
Expect.equals(1, 1 ?? 2);
|
|
Expect.equals(1, 1 ?? null);
|
|
Expect.equals(2, null ?? 2);
|
|
Expect.equals(null, null ?? null);
|
|
Expect.equals('B', (new B('B') ?? new C('C')).a);
|
|
Expect.equals('B', ((new B('B') ?? new C('C')) as dynamic).b);
|
|
Expect.throwsNoSuchMethodError(() => ((new B('B') ?? new C('C')) as dynamic).c);
|
|
Expect.equals('B', (new B('B') ?? nullC()).a);
|
|
Expect.equals('B', ((new B('B') ?? nullC()) as dynamic).b);
|
|
Expect.throwsNoSuchMethodError(() => ((new B('B') ?? nullC()) as dynamic).c);
|
|
Expect.equals('C', (nullB() ?? new C('C')).a);
|
|
Expect.throwsNoSuchMethodError(() => ((nullB() ?? new C('C')) as dynamic).b);
|
|
Expect.equals('C', ((nullB() ?? new C('C')) as dynamic).c);
|
|
Expect.throwsNoSuchMethodError(() => (nullB() ?? nullC()).a);
|
|
Expect.throwsNoSuchMethodError(() => ((nullB() ?? nullC()) as dynamic).b);
|
|
Expect.throwsNoSuchMethodError(() => ((nullB() ?? nullC()) as dynamic).c);
|
|
}
|