blob: 3a198d1e000f603df1eb834ef327ba41eb18ff53 [file] [log] [blame]
// 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.
// Verify that '??' binds tighter than '?:' and less tightly than '||'.
import "package:expect/expect.dart";
main() {
// Make sure the "none" test fails if "??" is not implemented. This makes
// status files easier to maintain.
var _ = null ?? null;
dynamic falsity = false;
dynamic truth = true;
dynamic one = 1;
dynamic two = 2;
// "a ?? b ?? c" should be legal, and should evaluate to the first non-null
// value (or null if there are no non-null values).
Expect.equals(1, one ?? two ?? 3);
Expect.equals(2, null ?? two ?? 3);
Expect.equals(3, null ?? null ?? 3);
Expect.equals(null, null ?? null ?? null);
// "a ?? b ? c : d" should parse as "(a ?? b) ? c : d", therefore provided
// that a is true, b need not be a bool. An incorrect parse of
// "a ?? (b ? c : d)" would require b to be a bool to avoid a static type
// warning.
Expect.equals(2, truth ?? 1 ? 2 : 3);
// "a ?? b || c" should parse as "a ?? (b || c)", therefore it's a static
// type warning if b doesn't have type bool. An incorrect parse of
// "(a ?? b) || c" would allow b to have any type provided that a is bool.
falsity ?? 1 || true;
// ^
// [analyzer] COMPILE_TIME_ERROR.NON_BOOL_OPERAND
// [cfe] A value of type 'int' can't be assigned to a variable of type 'bool'.
// "a || b ?? c" should parse as "(a || b) ?? c", therefore it is a static
// type warning if b doesn't have type bool. An incorrect parse of
// "a || (b ?? c)" would allow b to have any type provided that c is bool.
falsity || 1 ?? true;
// ^
// [cfe] Operand of null-aware operation '??' has type 'bool' which excludes null.
// ^
// [analyzer] COMPILE_TIME_ERROR.NON_BOOL_OPERAND
// [cfe] A value of type 'int' can't be assigned to a variable of type 'bool'.
// ^^^^
// [analyzer] STATIC_WARNING.DEAD_NULL_AWARE_EXPRESSION
// An incorrect parse of "a || (b ?? c)" would result in no checked-mode
// error.
Expect.throwsAssertionError(() => false || null ?? true);
// ^
// [cfe] Operand of null-aware operation '??' has type 'bool' which excludes null.
// ^^^^
// [analyzer] COMPILE_TIME_ERROR.NON_BOOL_OPERAND
// [cfe] The value 'null' can't be assigned to a variable of type 'bool' because 'bool' is not nullable.
// ^^^^
// [analyzer] STATIC_WARNING.DEAD_NULL_AWARE_EXPRESSION
}