[tests] Migrate multi-test to static error test

Remove compile time errors from null_test.dart and move them into
a new static error test file.

Add the other mixin application syntax.

This makes it so much easier to run and debug null_test.dart on a
backend.

Change-Id: I126a580ccf477962cd90dccff267034bd9b35a2b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/254722
Commit-Queue: Erik Ernst <[email protected]>
Auto-Submit: Nicholas Shahan <[email protected]>
Reviewed-by: Erik Ernst <[email protected]>

Author: nshahan

tests/language/null/inherit_static_errors_test.dart

@@ -0,0 +1,36 @@
+// Copyright (c) 2022, 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.
+
+class BadExtends extends Null {}
+//                       ^^^^
+// [analyzer] COMPILE_TIME_ERROR.SUBTYPE_OF_DISALLOWED_TYPE
+//    ^
+// [cfe] 'Null' is restricted and can't be extended or implemented.
+// [cfe] The superclass, 'Null', has no unnamed constructor that takes no arguments.
+//                       ^
+// [cfe] 'Null' is restricted and can't be extended or implemented.
+
+class BadImplements implements Null {}
+//                             ^^^^
+// [analyzer] COMPILE_TIME_ERROR.SUBTYPE_OF_DISALLOWED_TYPE
+//    ^
+// [cfe] 'Null' is restricted and can't be extended or implemented.
+//                             ^
+// [cfe] 'Null' is restricted and can't be extended or implemented.
+
+class BadMixin extends Object with Null {}
+//                                 ^^^^
+// [analyzer] COMPILE_TIME_ERROR.SUBTYPE_OF_DISALLOWED_TYPE
+//    ^
+// [cfe] 'Null' is restricted and can't be extended or implemented.
+//                                 ^
+// [cfe] 'Null' is restricted and can't be extended or implemented.
+
+class BadMixin2 = Object with Null;
+//                            ^^^^
+// [analyzer] COMPILE_TIME_ERROR.SUBTYPE_OF_DISALLOWED_TYPE
+//    ^
+// [cfe] 'Null' is restricted and can't be extended or implemented.
+//                            ^
+// [cfe] 'Null' is restricted and can't be extended or implemented.

tests/language/null/null_test.dart

@@ -7,12 +7,6 @@
 
 import "package:expect/expect.dart";
 
-class BadInherit
-  extends Null //    //# 01: compile-time error
-  implements Null // //# 02: compile-time error
-  extends Object with Null // //# 03: compile-time error
-{}
-
 class EqualsNotCalled {
   int get hashCode => throw "And don't warn!";
   bool operator ==(Object other) {
@@ -52,8 +46,6 @@ void main() {
 }
 
 void test() {
-  new BadInherit(); // Make sure class is referenced.
-
   void foo(var obj) {
     Expect.equals(null, obj);
   }

tests/language_2/null/inherit_static_errors_test.dart

@@ -0,0 +1,36 @@
+// Copyright (c) 2022, 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.
+
+class BadExtends extends Null {}
+//                       ^^^^
+// [analyzer] COMPILE_TIME_ERROR.SUBTYPE_OF_DISALLOWED_TYPE
+//    ^
+// [cfe] 'Null' is restricted and can't be extended or implemented.
+// [cfe] The superclass, 'Null', has no unnamed constructor that takes no arguments.
+//                       ^
+// [cfe] 'Null' is restricted and can't be extended or implemented.
+
+class BadImplements implements Null {}
+//                             ^^^^
+// [analyzer] COMPILE_TIME_ERROR.SUBTYPE_OF_DISALLOWED_TYPE
+//    ^
+// [cfe] 'Null' is restricted and can't be extended or implemented.
+//                             ^
+// [cfe] 'Null' is restricted and can't be extended or implemented.
+
+class BadMixin extends Object with Null {}
+//                                 ^^^^
+// [analyzer] COMPILE_TIME_ERROR.SUBTYPE_OF_DISALLOWED_TYPE
+//    ^
+// [cfe] 'Null' is restricted and can't be extended or implemented.
+//                                 ^
+// [cfe] 'Null' is restricted and can't be extended or implemented.
+
+class BadMixin2 = Object with Null;
+//                            ^^^^
+// [analyzer] COMPILE_TIME_ERROR.SUBTYPE_OF_DISALLOWED_TYPE
+//    ^
+// [cfe] 'Null' is restricted and can't be extended or implemented.
+//                            ^
+// [cfe] 'Null' is restricted and can't be extended or implemented.

tests/language_2/null/null_test.dart

@@ -9,12 +9,6 @@
 
 import "package:expect/expect.dart";
 
-class BadInherit
-  extends Null //    //# 01: compile-time error
-  implements Null // //# 02: compile-time error
-  extends Object with Null // //# 03: compile-time error
-{}
-
 class EqualsNotCalled {
   int get hashCode => throw "And don't warn!";
   bool operator ==(Object other) {
@@ -54,8 +48,6 @@ void main() {
 }
 
 void test() {
-  new BadInherit(); // Make sure class is referenced.
-
   int foo(var obj) {
     Expect.equals(null, obj);
   }