LanguageFeatures/Spread-collections/Syntax_A02_t11.dart

// 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.

// @dart = 2.9

/// @assertion The grammar changes for map and set are a little more complex
/// because of the potential ambiguity of collections containing only spreads.
/// The changed and new rules are:
///
///    setOrMapLiteral:
///    mapLiteral |
///    setLiteral |
///    mapOrSetLiteral
///    ;
///
///    mapLiteral:
///    const? typeArguments? '{' mapLiteralEntryList? '}'
///    ;
///
///    mapLiteralEntryList:
///    mapLiteralEntry ( ',' mapLiteralEntry )* ','?
///    ;
///
///    mapLiteralEntry:
///    expression ':' expression |
///    spread
///    ;
///
///    setLiteral:
///    'const'? typeArguments? '{' spreadableList '}' ;
///
///    mapOrSetLiteral:
///    'const'?  '{' spread (',' spread)* '}' ;
///
/// @description Checks that spreadable element can be null-aware in spreadable
/// map
/// @author iarkh@unipro.ru


import "../../Utils/expect.dart";

main() {
  Map nullMap = null;
  Map a = {};

  Expect.mapEquals({}, {...?nullMap});
  Expect.throws(() => a = {...nullMap});

  Expect.mapEquals({1: 1}, {1: 1, ...?nullMap});
  Expect.throws(() => a = {1: 1, ...nullMap});

  Expect.mapEquals({1: 1}, {...?nullMap, 1: 1});
  Expect.throws(() => a = {...nullMap, 1: 1});
}