Johnni Winther
38d7c7661d
In error reporting on assignability where the expression has type `Null` we use a special messages that doesn't state that "'Null' is nullable". Cases where `Null` is part of the type or where the expression of type `Null` is derived from a collection are not special cased. Closes #43998 Closes #44093 Change-Id: Ic0c79e6362f2365eb3fe8222ccd2ef8fac4f188d Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/170433 Commit-Queue: Johnni Winther <johnniwinther@google.com> Reviewed-by: Dmitry Stefantsov <dmitryas@google.com>
63 lines
2.6 KiB
Dart
63 lines
2.6 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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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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dynamic falsity = false;
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dynamic truth = true;
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dynamic one = 1;
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dynamic two = 2;
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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, one ?? two ?? 3);
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Expect.equals(2, null ?? two ?? 3);
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Expect.equals(3, null ?? null ?? 3);
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Expect.equals(null, null ?? null ?? null);
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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, truth ?? 1 ? 2 : 3);
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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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falsity ?? 1 || true;
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// ^
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// [analyzer] COMPILE_TIME_ERROR.NON_BOOL_OPERAND
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// [cfe] A value of type 'int' can't be assigned to a variable of type 'bool'.
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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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falsity || 1 ?? true;
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// ^
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// [cfe] Operand of null-aware operation '??' has type 'bool' which excludes null.
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// ^
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// [analyzer] COMPILE_TIME_ERROR.NON_BOOL_OPERAND
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// [cfe] A value of type 'int' can't be assigned to a variable of type 'bool'.
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// ^^^^
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// [analyzer] STATIC_WARNING.DEAD_NULL_AWARE_EXPRESSION
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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.throwsAssertionError(() => false || null ?? true);
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// ^
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// [cfe] Operand of null-aware operation '??' has type 'bool' which excludes null.
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// ^^^^
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// [analyzer] COMPILE_TIME_ERROR.NON_BOOL_OPERAND
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// [cfe] The value 'null' can't be assigned to a variable of type 'bool' because 'bool' is not nullable.
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// ^^^^
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// [analyzer] STATIC_WARNING.DEAD_NULL_AWARE_EXPRESSION
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}
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