| // Copyright (c) 2019, 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. |
| |
| /// @assertion Dynamic Semantics |
| /// The new dynamic semantics are a superset of the original behavior. To avoid |
| /// redundancy and handle nested uses, the semantics are expressed in terms of a |
| /// separate procedure below: |
| /// . . . |
| /// Maps |
| /// A map literal of the form [<K, V>{entry_1 ... entry_n}] is evaluated as |
| /// follows: |
| /// 1. Allocate a fresh instance [map] of a class that implements |
| /// [LinkedHashMap<K, V>]. |
| /// |
| /// 2. For each [element] in the map literal: |
| /// i. Evaluate [element] using the procedure below. |
| /// |
| /// 3. The result of the map literal expression is [map]. |
| /// . . . |
| /// To evaluate a collection [element]: |
| /// This procedure handles elements in both list and map literals because the |
| /// only difference is how a base expression element or entry element is handled. |
| /// The control flow parts are the same so are unified here. |
| /// . . . |
| /// 3. Else, if [element] is an asynchronous [await for-in] element: |
| /// |
| /// i. Evaluate the stream expression to a value [stream]. It is a dynamic |
| /// error if [stream] is not an instance of a class that implements |
| /// [Stream]. |
| /// ii. Create a new [Future], [streamDone]. |
| /// iii. Evaluate [await streamDone]. |
| /// iv. Listen to [stream]. On each data event [event] the stream sends: |
| /// a. If the [for-in] element declares a variable, create a fresh |
| /// [variable] for it. Otherwise, use the existing [variable] it |
| /// refers to. |
| /// b. Bind [event] to [variable]. |
| /// c. Evaluate the body element using this procedure in the scope of |
| /// [variable]. If this raises an exception, complete [streamDone] |
| /// with it as an error. |
| /// v. If the [for-in] element declares a variable, discard it. |
| /// vi. If [stream] raises an exception, complete [streamDone] with it as an |
| /// error. Otherwise, when all events in the stream are in the stream are |
| /// processed, complete [streamDone] with [null]. |
| /// . . . |
| /// @description Checks that if [element] of map literal is a an asynchronous |
| /// [await for-in] element, this element is evaluated using the specified |
| /// procedure. |
| /// @author ngl@unipro.ru |
| |
| import "dart:async"; |
| import "../../Utils/expect.dart"; |
| |
| main() async { |
| var m1 = [MapEntry(1, 'a'), MapEntry(2, 'b'), MapEntry(3, 'c'), |
| MapEntry(4, 'd')]; |
| var m2 = [MapEntry(true, 3.5), MapEntry(null, 3), MapEntry(4.1, false)]; |
| var map1exp = {1: 'a', 2: 'b', 3: 'c', 4: 'd', true: 3.5, null: 3, 4.1: false}; |
| |
| var s1 = new Stream.fromIterable(m1); |
| var s2 = new Stream.fromIterable(m2); |
| |
| var map1 = {await for (var v in s1) v.key: v.value, |
| await for (var v in s2) v.key: v.value}; |
| Expect.isTrue(map1 is Map<Object?, Object?>); |
| Expect.mapEquals(map1exp, map1); |
| } |