dart-lang#2956. Add more tests for the type void

Language/Types/Type_Void/implicit_usage_A01_t01.dart

@@ -0,0 +1,34 @@
+// Copyright (c) 2024, 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 Finally, we need to address situations involving implicit usage
+/// of an object whose static type can be `void`. It is a compile-time error for
+/// a for-in statement to have an iterator expression of type `T` such that
+/// `Iterator<void>` is the most specific instantiation of `Iterator` that is a
+/// superinterface of `T`, unless the iteration variable has type `void`.
+///
+/// @description Checks that it is a compile-time error if in a for-in loop type
+/// of the iterator expression is `Iterator<void>` and the type of the iteration
+/// variable is not `void`.
+/// @author sgrekhov22@gmail.com
+/// @issue 57078
+
+void main() {
+  List<void> list = <void>[1, 2, 3];
+  for (Object? i in list) {
+//                  ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+  }
+  for (dynamic i in list) {
+//                  ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+  }
+  for (Null i in list) {
+//               ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+  }
+}

Language/Types/Type_Void/implicit_usage_A01_t02.dart

@@ -0,0 +1,28 @@
+// Copyright (c) 2024, 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 Finally, we need to address situations involving implicit usage
+/// of an object whose static type can be `void`. It is a compile-time error for
+/// a for-in statement to have an iterator expression of type `T` such that
+/// `Iterator<void>` is the most specific instantiation of `Iterator` that is a
+/// superinterface of `T`, unless the iteration variable has type `void`.
+///
+/// @description Checks that it is not an error if in a for-in loop type of the
+/// iterator expression is `Iterator<void>` and the type of the iteration
+/// variable is `void`.
+/// @author sgrekhov22@gmail.com
+
+import '../../../Utils/expect.dart';
+
+void main() {
+  List<void> list = <void>[1, 2, 3];
+  int j = 0;
+  for (void i in list) {
+    Expect.equals(++j, i as int);
+  }
+  j = 0;
+  for (var i in list) {
+    Expect.equals(++j, i as int);
+  }
+}

Language/Types/Type_Void/implicit_usage_A02_t01.dart

@@ -0,0 +1,34 @@
+// Copyright (c) 2024, 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 Finally, we need to address situations involving implicit usage
+/// of an object whose static type can be `void`. ... It is a compile-time error
+/// for an asynchronous for-in statement to have a stream expression of type `T`
+/// such that `Stream<void>` is the most specific instantiation of `Stream` that
+/// is a superinterface of `T`, unless the iteration variable has type `void`.
+///
+/// @description Checks that it is a compile-time error if in an asynchronous
+/// for-in loop type of the iterator expression is `Stream<void>` and the type
+/// of the iteration variable is not `void`.
+/// @author sgrekhov22@gmail.com
+/// @issue 57078
+
+void main() async {
+  Stream<void> stream = Stream<void>.fromIterable([1, 2, 3]);
+  await for (Object? i in stream) {
+//                        ^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+  }
+  await for (dynamic i in stream) {
+//                        ^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+  }
+  await for (Null i in stream) {
+//                     ^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+  }
+}

Language/Types/Type_Void/implicit_usage_A02_t02.dart

@@ -0,0 +1,28 @@
+// Copyright (c) 2024, 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 Finally, we need to address situations involving implicit usage
+/// of an object whose static type can be `void`. ... It is a compile-time error
+/// for an asynchronous for-in statement to have a stream expression of type `T`
+/// such that `Stream<void>` is the most specific instantiation of `Stream` that
+/// is a superinterface of `T`, unless the iteration variable has type `void`.
+///
+/// @description Checks that it is not an error if in an asynchronous for-in
+/// loop type of the iterator expression is `Stream<void>` and the type of the
+/// iteration variable is `void`.
+/// @author sgrekhov22@gmail.com
+
+import '../../../Utils/expect.dart';
+
+void main() async {
+  Stream<void> stream = Stream<void>.fromIterable([1, 2, 3]);
+  int j = 0;
+  await for (void i in stream) {
+    Expect.equals(++j, i as int);
+  }
+  j = 0;
+  await for (var i in stream) {
+    Expect.equals(++j, i as int);
+  }
+}