#2641. Add tests for unchanged type declarations named _ (#2666)

LanguageFeatures/Wildcards/unchanged_A03_t01.dart

@@ -0,0 +1,20 @@
+// 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 type named `_` is still accessible and can be
+/// used.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+class _ {}
+
+main() {
+  _ v = _();
+  print(_);
+}

LanguageFeatures/Wildcards/unchanged_A03_t02.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 type named `_` is still accessible and can be
+/// used.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+mixin _ {}
+
+main() {
+  print(_);
+}

LanguageFeatures/Wildcards/unchanged_A03_t03.dart

@@ -0,0 +1,20 @@
+// 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 type named `_` is still accessible and can be
+/// used.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+enum _ {e1;}
+
+main() {
+  print(_);
+  print(_.e1);
+}

LanguageFeatures/Wildcards/unchanged_A03_t04.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 type named `_` is still accessible and can be
+/// used.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+extension type _(int id) {}
+
+main() {
+  print(_);
+}

LanguageFeatures/Wildcards/unchanged_A03_t05.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 type named `_` is still accessible and can be
+/// used.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+class A {}
+extension _ on A {
+  static int s = 42;
+}
+
+main() {
+  print(_.s);
+}

LanguageFeatures/Wildcards/unchanged_A03_t06.dart

@@ -0,0 +1,20 @@
+// 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 type alias named `_` is still accessible and can
+/// be used.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+class C {}
+typedef _ = C;
+
+main() {
+  print(_);
+}

LanguageFeatures/Wildcards/unchanged_A03_t07.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 type alias named `_` is still accessible and can
+/// be used.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+import '../../Utils/expect.dart';
+
+typedef int _(String s);
+
+main() {
+  _ f = (String s) {return 42;};
+  Expect.equals(42, f(""));
+}