[test] Porting mixin hot reload tests.

Change-Id: Ie9aedb99878cf4adb40949e8127c6e254dba1162
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/406061
Reviewed-by: Nate Biggs <[email protected]>
Commit-Queue: Mark Zhou <[email protected]>

Author: Markzipan

tests/hot_reload/imported_mixin_function/lib.0.dart

@@ -0,0 +1,7 @@
+// Copyright (c) 2025, 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.
+
+mixin ImportedMixin {
+  mixinFunc() => 'mixin';
+}

tests/hot_reload/imported_mixin_function/main.0.dart

@@ -0,0 +1,23 @@
+// Copyright (c) 2025, 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.
+
+import 'lib.dart' show ImportedMixin;
+import 'package:expect/expect.dart';
+import 'package:reload_test/reload_test_utils.dart';
+
+// Adapted from:
+// https://github.com/dart-lang/sdk/blob/1a486499bf73ee5b007abbe522b94869a1f36d02/runtime/vm/isolate_reload_test.cc#L1222
+
+// Verifies that we assign the correct patch classes for imported
+// mixins when we reload.
+
+class A extends Object with ImportedMixin {}
+
+var func = new A().mixinFunc;
+
+Future<void> main() async {
+  Expect.equals('mixin', func());
+  await hotReload();
+  Expect.equals('mixin', func());
+}

tests/hot_reload/imported_mixin_function/main.1.dart

@@ -0,0 +1,36 @@
+// Copyright (c) 2025, 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.
+
+import 'lib.dart' show ImportedMixin;
+import 'package:expect/expect.dart';
+import 'package:reload_test/reload_test_utils.dart';
+
+// Adapted from:
+// https://github.com/dart-lang/sdk/blob/1a486499bf73ee5b007abbe522b94869a1f36d02/runtime/vm/isolate_reload_test.cc#L1222
+
+// Verifies that we assign the correct patch classes for imported
+// mixins when we reload.
+
+class A extends Object with ImportedMixin {}
+
+var func;
+
+Future<void> main() async {
+  Expect.equals('mixin', func());
+  await hotReload();
+  Expect.equals('mixin', func());
+}
+
+/** DIFF **/
+/*
+@@ -14,7 +14,7 @@
+ 
+ class A extends Object with ImportedMixin {}
+ 
+-var func = new A().mixinFunc;
++var func;
+ 
+ Future<void> main() async {
+   Expect.equals('mixin', func());
+*/

tests/hot_reload/mixin_changed/main.0.dart

@@ -0,0 +1,31 @@
+// Copyright (c) 2025, 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.
+
+import 'package:expect/expect.dart';
+import 'package:reload_test/reload_test_utils.dart';
+
+// Adapted from:
+// https://github.com/dart-lang/sdk/blob/1a486499bf73ee5b007abbe522b94869a1f36d02/runtime/vm/isolate_reload_test.cc#L917
+
+mixin Mixin1 {
+  var field = 'mixin1';
+  func() => 'mixin1';
+}
+
+class B extends Object with Mixin1 {}
+
+Future<void> main() async {
+  var saved = B();
+  Expect.equals('mixin1', saved.field);
+  Expect.equals('mixin1', saved.func());
+  await hotReload();
+
+  // The saved instance of B retains its old field value from mixin1,
+  // but it gets the new implementation of func from mixin2.
+  var newer = B();
+  Expect.equals('mixin1', saved.field);
+  Expect.equals('mixin2', saved.func());
+  Expect.equals('mixin2', newer.field);
+  Expect.equals('mixin2', newer.func());
+}

tests/hot_reload/mixin_changed/main.1.dart

@@ -0,0 +1,52 @@
+// Copyright (c) 2025, 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.
+
+import 'package:expect/expect.dart';
+import 'package:reload_test/reload_test_utils.dart';
+
+// Adapted from:
+// https://github.com/dart-lang/sdk/blob/1a486499bf73ee5b007abbe522b94869a1f36d02/runtime/vm/isolate_reload_test.cc#L917
+
+mixin Mixin2 {
+  var field = 'mixin2';
+  func() => 'mixin2';
+}
+
+class B extends Object with Mixin2 {}
+
+Future<void> main() async {
+  var saved = B();
+  Expect.equals('mixin1', saved.field);
+  Expect.equals('mixin1', saved.func());
+  await hotReload();
+
+  // The saved instance of B retains its old field value from mixin1,
+  // but it gets the new implementation of func from mixin2.
+  var newer = B();
+  Expect.equals('mixin1', saved.field);
+  Expect.equals('mixin2', saved.func());
+  Expect.equals('mixin2', newer.field);
+  Expect.equals('mixin2', newer.func());
+}
+
+/** DIFF **/
+/*
+@@ -8,12 +8,12 @@
+ // Adapted from:
+ // https://github.com/dart-lang/sdk/blob/1a486499bf73ee5b007abbe522b94869a1f36d02/runtime/vm/isolate_reload_test.cc#L917
+ 
+-mixin Mixin1 {
+-  var field = 'mixin1';
+-  func() => 'mixin1';
++mixin Mixin2 {
++  var field = 'mixin2';
++  func() => 'mixin2';
+ }
+ 
+-class B extends Object with Mixin1 {}
++class B extends Object with Mixin2 {}
+ 
+ Future<void> main() async {
+   var saved = B();
+*/