Update code to Dart 3.0

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 * Require Dart 3.0.
 * Mark mixin classes as `mixin class`.
+* Added a `Map.pairs` extension method to make it easier to work with maps using
+  Dart 3 record types.
 
 ## 1.17.2
 

lib/collection.dart

@@ -17,6 +17,7 @@ export 'src/functions.dart';
 export 'src/iterable_extensions.dart';
 export 'src/iterable_zip.dart';
 export 'src/list_extensions.dart';
+export 'src/map_extensions.dart';
 export 'src/priority_queue.dart';
 export 'src/queue_list.dart';
 export 'src/union_set.dart';

lib/src/functions.dart

@@ -5,6 +5,7 @@
 import 'dart:collection';
 import 'dart:math' as math;
 
+import 'map_extensions.dart';
 import 'utils.dart';
 
 /// Creates a new map from [map] with new keys and values.

lib/src/map_extensions.dart

@@ -0,0 +1,8 @@
+// Copyright (c) 2023, 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.
+
+extension MapExtensions<K, V> on Map<K, V> {
+  /// Like [Map.entries], but returns each entry as a record.
+  Iterable<(K, V)> get pairs => entries.map((e) => (e.key, e.value));
+}

test/extensions_test.dart

@@ -1900,6 +1900,23 @@ void main() {
       });
     });
   });
+
+  group('Map', () {
+    group('pairs', () {
+      test('empty map', () {
+        expect(<int, int>{}.pairs, isEmpty);
+      });
+
+      test('single pair', () {
+        expect(<int, int>{1: 2}.pairs, equals([(1, 2)]));
+      });
+
+      test('multiple pairs', () {
+        expect(<int, int>{1: 2, 3: 4, 5: 6}.pairs,
+            equals([(1, 2), (3, 4), (5, 6)]));
+      });
+    });
+  });
 }
 
 /// Creates a plain iterable not implementing any other class.