feat(types): add new pair type

packages/wyatt_type_utils/lib/src/pair/pair.dart

@@ -0,0 +1,56 @@
+// Copyright (C) 2022 WYATT GROUP
+// Please see the AUTHORS file for details.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+extension PairExtension<T> on Pair<T, T> {
+  List<T?> toList() => List.from([left, right]);
+}
+
+/// {@template pair}
+/// [Pair] is a simple object which contains pair of two values.
+/// {@endtemplate}
+class Pair<L, R> {
+  final L? left;
+  final R? right;
+
+  /// {@macro pair}
+  const Pair(this.left, this.right);
+
+  @override
+  String toString() => '($left, $right)';
+
+  Pair<L, R> copyWith({
+    L? left,
+    R? right,
+  }) =>
+      Pair<L, R>(
+        left ?? this.left,
+        right ?? this.right,
+      );
+
+  @override
+  // ignore: avoid_equals_and_hash_code_on_mutable_classes
+  bool operator ==(covariant Pair<L, R> other) {
+    if (identical(this, other)) {
+      return true;
+    }
+
+    return other.left == left && other.right == right;
+  }
+
+  @override
+  // ignore: avoid_equals_and_hash_code_on_mutable_classes
+  int get hashCode => left.hashCode ^ right.hashCode;
+}