dart-lang#2641. Add tests for unchanged declarations named _

LanguageFeatures/Wildcards/unchanged_A01_t01.dart

@@ -0,0 +1,22 @@
+// 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 Other declarations: top-level variables, top-level function
+/// names, type names, member names, etc. are unchanged. They can be named `_`
+/// as they are today.
+///
+/// @description Checks that a top-level variable named `_` is still accessible
+/// and its value can be used.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+import '../../Utils/expect.dart';
+
+var _;
+
+main() {
+  _ = "value";
+  Expect.equals("value", _);
+}

LanguageFeatures/Wildcards/unchanged_A01_t02.dart

@@ -0,0 +1,21 @@
+// 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 Other declarations: top-level variables, top-level function
+/// names, type names, member names, etc. are unchanged. They can be named `_`
+/// as they are today.
+///
+/// @description Checks that a top-level variable named `_` is still accessible
+/// and its value can be used.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+import '../../Utils/expect.dart';
+
+final _ = 42;
+
+main() {
+  Expect.equals(42, _);
+}

LanguageFeatures/Wildcards/unchanged_A01_t03.dart

@@ -0,0 +1,21 @@
+// 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 Other declarations: top-level variables, top-level function
+/// names, type names, member names, etc. are unchanged. They can be named `_`
+/// as they are today.
+///
+/// @description Checks that a top-level variable named `_` is still accessible
+/// and its value can be used.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+import '../../Utils/expect.dart';
+
+int _ = 42;
+
+main() {
+  Expect.equals(42, _);
+}

LanguageFeatures/Wildcards/unchanged_A01_t04.dart

@@ -0,0 +1,21 @@
+// 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 Other declarations: top-level variables, top-level function
+/// names, type names, member names, etc. are unchanged. They can be named `_`
+/// as they are today.
+///
+/// @description Checks that it is a compile-time error to declare more than one
+/// top-level variable named `_`.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+var _, _;
+//     ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+main() {
+}

LanguageFeatures/Wildcards/unchanged_A01_t05.dart

@@ -0,0 +1,21 @@
+// 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 Other declarations: top-level variables, top-level function
+/// names, type names, member names, etc. are unchanged. They can be named `_`
+/// as they are today.
+///
+/// @description Checks that it is a compile-time error to declare more than one
+/// top-level variable named `_`.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+final _ = 1, _ = 2;
+//           ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+main() {
+}

LanguageFeatures/Wildcards/unchanged_A01_t06.dart

@@ -0,0 +1,21 @@
+// 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 Other declarations: top-level variables, top-level function
+/// names, type names, member names, etc. are unchanged. They can be named `_`
+/// as they are today.
+///
+/// @description Checks that it is a compile-time error to declare more than one
+/// top-level variable named `_`.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+int? _ = 42, _;
+//           ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+main() {
+}

LanguageFeatures/Wildcards/unchanged_A01_t07.dart

@@ -0,0 +1,27 @@
+// 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 Other declarations: top-level variables, top-level function
+/// names, type names, member names, etc. are unchanged. They can be named `_`
+/// as they are today.
+///
+/// @description Checks that it is a compile-time error to declare more than one
+/// top-level variable named `_`.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+const _ = 42;
+final _ = 43;
+//    ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+var _;
+//  ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+main() {
+}

LanguageFeatures/Wildcards/unchanged_A02_t01.dart

@@ -0,0 +1,22 @@
+// 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 Other declarations: top-level variables, top-level function
+/// names, type names, member names, etc. are unchanged. They can be named `_`
+/// as they are today.
+///
+/// @description Checks that a top-level function named `_` is still accessible
+/// and can be called.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+import '../../Utils/expect.dart';
+
+int _() => 42;
+
+main() {
+  print(_);
+  Expect.equals(42, _());
+}

LanguageFeatures/Wildcards/unchanged_A02_t02.dart

@@ -0,0 +1,21 @@
+// 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 Other declarations: top-level variables, top-level function
+/// names, type names, member names, etc. are unchanged. They can be named `_`
+/// as they are today.
+///
+/// @description Checks that a top-level getter named `_` is still accessible
+/// and can be called.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+import '../../Utils/expect.dart';
+
+int get _ => 42;
+
+main() {
+  Expect.equals(42, _);
+}

LanguageFeatures/Wildcards/unchanged_A02_t03.dart

@@ -0,0 +1,22 @@
+// 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 Other declarations: top-level variables, top-level function
+/// names, type names, member names, etc. are unchanged. They can be named `_`
+/// as they are today.
+///
+/// @description Checks that it is a compile-time error to declare more than one
+/// top-level function named `_`.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+int _() => 42;
+int _() => 43;
+//  ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+main() {
+}

LanguageFeatures/Wildcards/unchanged_A02_t04.dart

@@ -0,0 +1,22 @@
+// 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 Other declarations: top-level variables, top-level function
+/// names, type names, member names, etc. are unchanged. They can be named `_`
+/// as they are today.
+///
+/// @description Checks that it is a compile-time error to declare more than one
+/// top-level getter named `_`.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+int get _ => 42;
+int get _ => 43;
+//      ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+main() {
+}

LanguageFeatures/Wildcards/unchanged_A02_t05.dart

@@ -0,0 +1,19 @@
+// 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 Other declarations: top-level variables, top-level function
+/// names, type names, member names, etc. are unchanged. They can be named `_`
+/// as they are today.
+///
+/// @description Checks that a top-level setter named `_` is still accessible
+/// and can be called.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+void set _(int v) {}
+
+main() {
+  _ = 42;
+}

LanguageFeatures/Wildcards/unchanged_A02_t06.dart

@@ -0,0 +1,22 @@
+// 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 Other declarations: top-level variables, top-level function
+/// names, type names, member names, etc. are unchanged. They can be named `_`
+/// as they are today.
+///
+/// @description Checks that it is a compile-time error to declare more than one
+/// top-level setter named `_`.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+void set _(int v) {}
+void set _(int v) {}
+//       ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+main() {
+}