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1 // Copyright (c) 2015, the Dart project authors. Please see the AUTHORS file | 1 // Copyright (c) 2015, the Dart project authors. Please see the AUTHORS file |
2 // for details. All rights reserved. Use of this source code is governed by a | 2 // for details. All rights reserved. Use of this source code is governed by a |
3 // BSD-style license that can be found in the LICENSE file. | 3 // BSD-style license that can be found in the LICENSE file. |
4 | 4 |
5 // Verify that '??' binds tighter than '?:' and less tightly than '||'. | 5 // Verify that '??' binds tighter than '?:' and less tightly than '||'. |
6 | 6 |
7 import "package:expect/expect.dart"; | 7 import "package:expect/expect.dart"; |
8 | 8 |
9 assertionError(e) => e is AssertionError; | 9 assertionError(e) => e is AssertionError; |
10 | 10 |
11 // Determine whether the VM is running in checked mode. | 11 // Determine whether the VM is running in checked mode. |
12 bool get checkedMode { | 12 bool get checkedMode { |
13 try { | 13 try { |
14 var x = 'foo'; | 14 var x = 'foo'; |
15 int y = x; | 15 int y = x; |
16 return false; | 16 return false; |
17 } catch (_) { | 17 } catch (_) { |
18 return true; | 18 return true; |
19 } | 19 } |
20 } | 20 } |
21 | 21 |
22 main() { | 22 main() { |
23 // Make sure the "none" test fails if "??" is not implemented. This makes | 23 // Make sure the "none" test fails if "??" is not implemented. This makes |
24 // status files easier to maintain. | 24 // status files easier to maintain. |
25 var _ = null ?? null; | 25 var _ = null ?? null; |
26 | 26 |
27 // "a ?? b ?? c" should be legal, and should evaluate to the first non-null | 27 // "a ?? b ?? c" should be legal, and should evaluate to the first non-null |
28 // value (or null if there are no non-null values). | 28 // value (or null if there are no non-null values). |
29 Expect.equals(1, 1 ?? 2 ?? 3); /// 01: ok | 29 Expect.equals(1, 1 ?? 2 ?? 3); //# 01: ok |
30 Expect.equals(2, null ?? 2 ?? 3); /// 02: ok | 30 Expect.equals(2, null ?? 2 ?? 3); //# 02: ok |
31 Expect.equals(3, null ?? null ?? 3); /// 03: ok | 31 Expect.equals(3, null ?? null ?? 3); //# 03: ok |
32 Expect.equals(null, null ?? null ?? null); /// 04: ok | 32 Expect.equals(null, null ?? null ?? null); //# 04: ok |
33 | 33 |
34 // "a ?? b ? c : d" should parse as "(a ?? b) ? c : d", therefore provided | 34 // "a ?? b ? c : d" should parse as "(a ?? b) ? c : d", therefore provided |
35 // that a is true, b need not be a bool. An incorrect parse of | 35 // that a is true, b need not be a bool. An incorrect parse of |
36 // "a ?? (b ? c : d)" would require b to be a bool to avoid a static type | 36 // "a ?? (b ? c : d)" would require b to be a bool to avoid a static type |
37 // warning. | 37 // warning. |
38 Expect.equals(2, true ?? 1 ? 2 : 3); /// 05: ok | 38 Expect.equals(2, true ?? 1 ? 2 : 3); //# 05: ok |
39 | 39 |
40 // "a ?? b || c" should parse as "a ?? (b || c)", therefore it's a static | 40 // "a ?? b || c" should parse as "a ?? (b || c)", therefore it's a static |
41 // type warning if b doesn't have type bool. An incorrect parse of | 41 // type warning if b doesn't have type bool. An incorrect parse of |
42 // "(a ?? b) || c" would allow b to have any type provided that a is bool. | 42 // "(a ?? b) || c" would allow b to have any type provided that a is bool. |
43 Expect.equals(false, false ?? 1 || true); /// 06: static type warning | 43 Expect.equals(false, false ?? 1 || true); //# 06: static type warning |
44 | 44 |
45 // "a || b ?? c" should parse as "(a || b) ?? c", therefore it is a static | 45 // "a || b ?? c" should parse as "(a || b) ?? c", therefore it is a static |
46 // type warning if b doesn't have type bool. An incorrect parse of | 46 // type warning if b doesn't have type bool. An incorrect parse of |
47 // "a || (b ?? c)" would allow b to have any type provided that c is bool. | 47 // "a || (b ?? c)" would allow b to have any type provided that c is bool. |
48 if (checkedMode) { | 48 if (checkedMode) { |
49 Expect.throws(() => false || 1 ?? true, assertionError); /// 07: static type
warning | 49 Expect.throws(() => false || 1 ?? true, assertionError); //# 07: static type
warning |
50 } else { | 50 } else { |
51 Expect.equals(false, false || 1 ?? true); // /// 07: continued | 51 Expect.equals(false, false || 1 ?? true); // //# 07: continued |
52 } | 52 } |
53 | 53 |
54 if (checkedMode) { | 54 if (checkedMode) { |
55 // An incorrect parse of "a || (b ?? c)" would result in no checked-mode | 55 // An incorrect parse of "a || (b ?? c)" would result in no checked-mode |
56 // error. | 56 // error. |
57 Expect.throws(() => false || null ?? true, assertionError); /// 08: ok | 57 Expect.throws(() => false || null ?? true, assertionError); //# 08: ok |
58 } else { | 58 } else { |
59 // An incorrect parse of "a || (b ?? c)" would result in c being evaluated. | 59 // An incorrect parse of "a || (b ?? c)" would result in c being evaluated. |
60 int i = 0; // /// 08: contin
ued | 60 int i = 0; // //# 08: contin
ued |
61 Expect.equals(false, false || null ?? i++ == 0); // /// 08: contin
ued | 61 Expect.equals(false, false || null ?? i++ == 0); // //# 08: contin
ued |
62 Expect.equals(0, i); // /// 08: contin
ued | 62 Expect.equals(0, i); // //# 08: contin
ued |
63 } | 63 } |
64 } | 64 } |
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