[tests] Porting instance and hierarchy change tests to the hot reload framework.

Change-Id: I7a11a43d34772f2020dda235327da71fa388f3ad
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/406062
Commit-Queue: Mark Zhou <markzipan@google.com>
Reviewed-by: Nicholas Shahan <nshahan@google.com>

tests/hot_reload/change_instance_format0/main.0.dart

@@ -0,0 +1,30 @@
+// 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#L3806
+
+// Tests reload succeeds when instance format changes.
+// Change: Foo {a, b, c:42}  -> Foo {c:42}
+// Validate: c keeps the value in the retained Foo object.
+
+class Foo {
+  var a;
+  var b;
+  var c;
+}
+
+var f;
+
+Future<void> main() async {
+  f = Foo();
+  f.c = 42;
+  Expect.equals(42, f.c);
+  await hotReload();
+
+  Expect.equals(42, f.c);
+}

tests/hot_reload/change_instance_format0/main.1.dart

@@ -0,0 +1,40 @@
+// 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#L3806
+
+// Tests reload succeeds when instance format changes.
+// Change: Foo {a, b, c:42}  -> Foo {c:42}
+// Validate: c keeps the value in the retained Foo object.
+
+class Foo {
+  var c;
+}
+
+var f;
+
+Future<void> main() async {
+  f = Foo();
+  f.c = 42;
+  Expect.equals(42, f.c);
+  await hotReload();
+
+  Expect.equals(42, f.c);
+}
+
+/** DIFF **/
+/*
+ // Validate: c keeps the value in the retained Foo object.
+ 
+ class Foo {
+-  var a;
+-  var b;
+   var c;
+ }
+ 
+*/

tests/hot_reload/change_instance_format1/main.0.dart

@@ -0,0 +1,24 @@
+// 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#L3841
+
+// Tests reload succeeds when instance format changes.
+// Change: Foo {}  -> Foo {c:null}
+// Validate: c is initialized to null the retained Foo object.
+
+class Foo {}
+
+var f;
+
+Future<void> main() async {
+  f = Foo();
+  await hotReload();
+
+  Expect.isNull(f.c);
+}

tests/hot_reload/change_instance_format1/main.1.dart

@@ -0,0 +1,40 @@
+// 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#L3841
+
+// Tests reload succeeds when instance format changes.
+// Change: Foo {}  -> Foo {c:null}
+// Validate: c is initialized to null the retained Foo object.
+
+class Foo {
+  var c;
+}
+
+var f;
+
+Future<void> main() async {
+  f = Foo();
+  await hotReload();
+
+  Expect.isNull(f.c);
+}
+
+/** DIFF **/
+/*
+ // Change: Foo {}  -> Foo {c:null}
+ // Validate: c is initialized to null the retained Foo object.
+ 
+-class Foo {}
++class Foo {
++  var c;
++}
+ 
+ var f;
+ 
+*/

tests/hot_reload/change_instance_format2/main.0.dart

@@ -0,0 +1,28 @@
+// 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#L3872
+
+// Tests reload succeeds when instance format changes.
+// Change: Foo {c:42}  -> Foo {}
+// Validate: running the after script fails.
+
+class Foo {
+  var c;
+}
+
+var f;
+
+Future<void> main() async {
+  f = Foo();
+  f.c = 42;
+  Expect.equals(42, f.c);
+  await hotReload();
+
+  Expect.throws<NoSuchMethodError>(() => f.c);
+}

tests/hot_reload/change_instance_format2/main.1.dart

@@ -0,0 +1,40 @@
+// 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#L3872
+
+// Tests reload succeeds when instance format changes.
+// Change: Foo {c:42}  -> Foo {}
+// Validate: running the after script fails.
+
+class Foo {}
+
+var f;
+
+Future<void> main() async {
+  f = Foo();
+  f.c = 42;
+  Expect.equals(42, f.c);
+  await hotReload();
+
+  Expect.throws<NoSuchMethodError>(() => f.c);
+}
+
+/** DIFF **/
+/*
+ // Change: Foo {c:42}  -> Foo {}
+ // Validate: running the after script fails.
+ 
+-class Foo {
+-  var c;
+-}
++class Foo {}
+ 
+ var f;
+ 
+*/

tests/hot_reload/change_instance_format3/main.0.dart

@@ -0,0 +1,38 @@
+// 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#L3908
+
+// Tests reload succeeds when instance format changes.
+// Change: Foo {a, b, c:42, d}  -> Foo {c:42, g}
+// Validate: c keeps the value in the retained Foo object.
+
+class Foo<A, B> {
+  var a;
+  var b;
+  var c;
+  var d;
+}
+
+helper() {
+  f = Foo();
+  f.a = 1;
+  f.b = 2;
+  f.c = 3;
+  f.d = 4;
+}
+
+var f;
+
+Future<void> main() async {
+  helper();
+  Expect.equals(3, f.c);
+  await hotReload();
+
+  Expect.equals(3, f.c);
+}

tests/hot_reload/change_instance_format3/main.1.dart

@@ -0,0 +1,55 @@
+// 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#L3908
+
+// Tests reload succeeds when instance format changes.
+// Change: Foo {a, b, c:42, d}  -> Foo {c:42, g}
+// Validate: c keeps the value in the retained Foo object.
+
+class Foo<A, B> {
+  var c;
+  var g;
+}
+
+helper() {}
+
+var f;
+
+Future<void> main() async {
+  helper();
+  Expect.equals(3, f.c);
+  await hotReload();
+
+  Expect.equals(3, f.c);
+}
+
+/** DIFF **/
+/*
+ // Validate: c keeps the value in the retained Foo object.
+ 
+ class Foo<A, B> {
+-  var a;
+-  var b;
+   var c;
+-  var d;
++  var g;
+ }
+ 
+-helper() {
+-  f = Foo();
+-  f.a = 1;
+-  f.b = 2;
+-  f.c = 3;
+-  f.d = 4;
+-}
++helper() {}
+ 
+ var f;
+ 
+*/

tests/hot_reload/change_instance_format4/main.0.dart

@@ -0,0 +1,33 @@
+// 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#L3948
+
+// Tests reload succeeds when instance format changes.
+// Change: Bar {c:42}, Foo : Bar {d, e} -> Foo {c:42}
+// Validate: c keeps the value in the retained Foo object.
+
+class Bar {
+  var c;
+}
+
+class Foo extends Bar {
+  var d;
+  var e;
+}
+
+var f;
+
+Future<void> main() async {
+  f = Foo();
+  f.c = 42;
+  Expect.equals(42, f.c);
+  await hotReload();
+
+  Expect.equals(42, f.c);
+}

tests/hot_reload/change_instance_format4/main.1.dart

@@ -0,0 +1,48 @@
+// 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#L3948
+
+// Tests reload succeeds when instance format changes.
+// Change: Bar {c:42}, Foo : Bar {d, e} -> Foo {c:42}
+// Validate: c keeps the value in the retained Foo object.
+
+class Foo {
+  var c;
+}
+
+var f;
+
+Future<void> main() async {
+  f = Foo();
+  f.c = 42;
+  Expect.equals(42, f.c);
+  await hotReload();
+
+  Expect.equals(42, f.c);
+}
+
+/** DIFF **/
+/*
+ // Change: Bar {c:42}, Foo : Bar {d, e} -> Foo {c:42}
+ // Validate: c keeps the value in the retained Foo object.
+ 
+-class Bar {
++class Foo {
+   var c;
+ }
+ 
+-class Foo extends Bar {
+-  var d;
+-  var e;
+-}
+-
+ var f;
+ 
+ Future<void> main() async {
+*/

tests/hot_reload/change_instance_format5/main.0.dart

@@ -0,0 +1,33 @@
+// 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#L3985
+
+// Tests reload succeeds when instance format changes.
+// Change: Bar {a, b}, Foo : Bar {c:42} -> Bar {c:42}, Foo : Bar {}
+// Validate: c keeps the value in the retained Foo object.
+
+class Bar {
+  var a;
+  var b;
+}
+
+class Foo extends Bar {
+  var c;
+}
+
+var f;
+
+Future<void> main() async {
+  f = Foo();
+  f.c = 42;
+  Expect.equals(42, f.c);
+  await hotReload();
+
+  Expect.equals(42, f.c);
+}

tests/hot_reload/change_instance_format5/main.1.dart

@@ -0,0 +1,50 @@
+// 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#L3985
+
+// Tests reload succeeds when instance format changes.
+// Change: Bar {a, b}, Foo : Bar {c:42} -> Bar {c:42}, Foo : Bar {}
+// Validate: c keeps the value in the retained Foo object.
+
+class Bar {
+  var c;
+}
+
+class Foo extends Bar {}
+
+var f;
+
+Future<void> main() async {
+  f = Foo();
+  f.c = 42;
+  Expect.equals(42, f.c);
+  await hotReload();
+
+  Expect.equals(42, f.c);
+}
+
+/** DIFF **/
+/*
+ // Validate: c keeps the value in the retained Foo object.
+ 
+ class Bar {
+-  var a;
+-  var b;
+-}
+-
+-class Foo extends Bar {
+   var c;
+ }
+ 
++class Foo extends Bar {}
++
+ var f;
+ 
+ Future<void> main() async {
+*/

tests/hot_reload/change_instance_format6/config.json

@@ -0,0 +1,6 @@
+{
+  "expectedErrors": {
+    "1": "type parameters have changed"
+  }
+}
+

tests/hot_reload/change_instance_format6/main.0.dart

@@ -0,0 +1,25 @@
+// 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#L4024
+
+// Tests reload fails when type parameters change.
+// Change: Foo<A,B> {a, b}  -> Foo<A> {a}
+// Validate: the right error message is returned.
+
+class Foo<A, B> {
+  var a;
+  var b;
+}
+
+Future<void> main() async {
+  Foo();
+  await hotReload(expectRejection: true);
+
+  Foo();
+}

tests/hot_reload/change_instance_format6/main.1.reject.dart

@@ -0,0 +1,38 @@
+// 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#L4024
+
+// Tests reload fails when type parameters change.
+// Change: Foo<A,B> {a, b}  -> Foo<A> {a}
+// Validate: the right error message is returned.
+
+class Foo<A> {
+  var a;
+}
+
+Future<void> main() async {
+  Foo();
+  await hotReload(expectRejection: true);
+
+  Foo();
+}
+
+/** DIFF **/
+/*
+ // Change: Foo<A,B> {a, b}  -> Foo<A> {a}
+ // Validate: the right error message is returned.
+ 
+-class Foo<A, B> {
++class Foo<A> {
+   var a;
+-  var b;
+ }
+ 
+ Future<void> main() async {
+*/

tests/hot_reload/change_instance_format7/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 '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#L4051
+
+// Tests reload succeeds when type parameters are changed for allocated class.
+// Change: Foo<A,B> {a, b} -> Foo<A> {a}
+// Validate: return value from main is correct.
+// Please note: This test works because no instances are created from Foo.
+
+class Foo<A, B> {
+  var a;
+  var b;
+}
+
+Future<void> main() async {
+  await hotReload();
+}

tests/hot_reload/change_instance_format7/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 '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#L4051
+
+// Tests reload succeeds when type parameters are changed for allocated class.
+// Change: Foo<A,B> {a, b} -> Foo<A> {a}
+// Validate: return value from main is correct.
+// Please note: This test works because no instances are created from Foo.
+
+class Foo<A> {
+  var a;
+}
+
+Future<void> main() async {
+  await hotReload();
+}
+
+/** DIFF **/
+/*
+ // Validate: return value from main is correct.
+ // Please note: This test works because no instances are created from Foo.
+ 
+-class Foo<A, B> {
++class Foo<A> {
+   var a;
+-  var b;
+ }
+ 
+ Future<void> main() async {
+*/

tests/hot_reload/change_instance_format8/main.0.dart

@@ -0,0 +1,33 @@
+// 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#L4071
+
+// Regression for handle sharing bug: Change the shape of two classes and see
+// that their instances don't change class.
+
+class A {
+  var x;
+}
+
+class B {
+  var x, y, z, w;
+}
+
+var a, b;
+
+Future<void> main() async {
+  a = A();
+  b = B();
+  Expect.type<A>(a);
+  Expect.type<B>(b);
+  await hotReload();
+
+  Expect.type<A>(a);
+  Expect.type<B>(b);
+}

tests/hot_reload/change_instance_format8/main.1.dart

@@ -0,0 +1,50 @@
+// 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#L4071
+
+// Regression for handle sharing bug: Change the shape of two classes and see
+// that their instances don't change class.
+
+class A {
+  var x, y;
+}
+
+class B {
+  var x, y, z, w, v;
+}
+
+var a, b;
+
+Future<void> main() async {
+  a = A();
+  b = B();
+  Expect.type<A>(a);
+  Expect.type<B>(b);
+  await hotReload();
+
+  Expect.type<A>(a);
+  Expect.type<B>(b);
+}
+
+/** DIFF **/
+/*
+ // that their instances don't change class.
+ 
+ class A {
+-  var x;
++  var x, y;
+ }
+ 
+ class B {
+-  var x, y, z, w;
++  var x, y, z, w, v;
+ }
+ 
+ var a, b;
+*/

tests/hot_reload/change_instance_format9/config.json

@@ -0,0 +1,6 @@
+{
+  "expectedErrors": {
+    "1": "type parameters have changed"
+  }
+}
+

tests/hot_reload/change_instance_format9/main.0.dart

@@ -0,0 +1,28 @@
+// 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#L4110
+
+// Tests reload fails when type arguments change.
+// Change: Baz extends Foo<String> -> Baz extends Bar<String, double>
+// Validate: the right error message is returned.
+
+class Foo<A> {
+  var a;
+}
+
+class Bar<B, C> extends Foo<B> {}
+
+class Baz extends Foo<String> {}
+
+Future<void> main() async {
+  Baz();
+  await hotReload(expectRejection: true);
+
+  Baz();
+}

tests/hot_reload/change_instance_format9/main.1.reject.dart

@@ -0,0 +1,40 @@
+// 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#L4110
+
+// Tests reload fails when type arguments change.
+// Change: Baz extends Foo<String> -> Baz extends Bar<String, double>
+// Validate: the right error message is returned.
+
+class Foo<A> {
+  var a;
+}
+
+class Bar<B, C> extends Foo<B> {}
+
+class Baz extends Bar<String, double> {}
+
+Future<void> main() async {
+  Baz();
+  await hotReload(expectRejection: true);
+
+  Baz();
+}
+
+/** DIFF **/
+/*
+ 
+ class Bar<B, C> extends Foo<B> {}
+ 
+-class Baz extends Foo<String> {}
++class Baz extends Bar<String, double> {}
+ 
+ Future<void> main() async {
+   Baz();
+*/

tests/hot_reload/complex_inheritance_change/main.0.dart

@@ -0,0 +1,51 @@
+// 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#L959
+
+class A {
+  String name;
+  A(this.name);
+}
+
+class B extends A {
+  B(name) : super(name);
+}
+
+class C extends B {
+  C(name) : super(name);
+}
+
+helper() {}
+
+var list = <dynamic>[A('a'), B('b'), C('c')];
+
+check() {
+  Expect.type<A>(list[0]);
+  Expect.notType<B>(list[0]);
+  Expect.notType<C>(list[0]);
+  Expect.type<A>(list[1]);
+  Expect.type<B>(list[1]);
+  Expect.notType<C>(list[1]);
+  Expect.type<A>(list[2]);
+  Expect.type<B>(list[2]);
+  Expect.type<C>(list[2]);
+}
+
+Future<void> main() async {
+  check();
+  await hotReload();
+
+  helper();
+  check();
+  await hotReload();
+
+  // Revive the class B and make sure all allocated instances take
+  // their place in the inheritance hierarchy.
+  check();
+}

tests/hot_reload/complex_inheritance_change/main.1.dart

@@ -0,0 +1,112 @@
+// 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#L959
+
+class C {
+  String name;
+  C(this.name);
+}
+
+class X extends C {
+  X(name) : super(name);
+}
+
+class A extends X {
+  A(name) : super(name);
+}
+
+helper() {
+  list.add(new X('x'));
+}
+
+var list;
+
+check() {
+  Expect.type<A>(list[0]);
+  Expect.type<C>(list[0]);
+  Expect.type<X>(list[0]);
+  Expect.type<A>(list[1]);
+  Expect.type<C>(list[1]);
+  Expect.type<X>(list[1]);
+  Expect.notType<A>(list[2]);
+  Expect.type<C>(list[2]);
+  Expect.notType<X>(list[2]);
+  Expect.notType<A>(list[3]);
+  Expect.type<C>(list[3]);
+  Expect.type<X>(list[3]);
+}
+
+Future<void> main() async {
+  check();
+  await hotReload();
+
+  helper();
+  check();
+  await hotReload();
+
+  // Revive the class B and make sure all allocated instances take
+  // their place in the inheritance hierarchy.
+  check();
+}
+
+/** DIFF **/
+/*
+ // Adapted from:
+ // https://github.com/dart-lang/sdk/blob/1a486499bf73ee5b007abbe522b94869a1f36d02/runtime/vm/isolate_reload_test.cc#L959
+ 
+-class A {
++class C {
+   String name;
+-  A(this.name);
++  C(this.name);
+ }
+ 
+-class B extends A {
+-  B(name) : super(name);
++class X extends C {
++  X(name) : super(name);
+ }
+ 
+-class C extends B {
+-  C(name) : super(name);
++class A extends X {
++  A(name) : super(name);
+ }
+ 
+-helper() {}
++helper() {
++  list.add(new X('x'));
++}
+ 
+-var list = <dynamic>[A('a'), B('b'), C('c')];
++var list;
+ 
+ check() {
+   Expect.type<A>(list[0]);
+-  Expect.notType<B>(list[0]);
+-  Expect.notType<C>(list[0]);
++  Expect.type<C>(list[0]);
++  Expect.type<X>(list[0]);
+   Expect.type<A>(list[1]);
+-  Expect.type<B>(list[1]);
+-  Expect.notType<C>(list[1]);
+-  Expect.type<A>(list[2]);
+-  Expect.type<B>(list[2]);
++  Expect.type<C>(list[1]);
++  Expect.type<X>(list[1]);
++  Expect.notType<A>(list[2]);
+   Expect.type<C>(list[2]);
++  Expect.notType<X>(list[2]);
++  Expect.notType<A>(list[3]);
++  Expect.type<C>(list[3]);
++  Expect.type<X>(list[3]);
+ }
+ 
+ Future<void> main() async {
+*/

tests/hot_reload/complex_inheritance_change/main.2.dart

@@ -0,0 +1,123 @@
+// 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#L959
+
+class X {
+  String name;
+  X(this.name);
+}
+
+class A extends X {
+  A(name) : super(name);
+}
+
+class B extends X {
+  B(name) : super(name);
+}
+
+class C extends A {
+  C(name) : super(name);
+}
+
+helper() {}
+
+var list;
+
+check() {
+  Expect.type<A>(list[0]);
+  Expect.notType<B>(list[0]);
+  Expect.notType<C>(list[0]);
+  Expect.type<X>(list[0]);
+  Expect.notType<A>(list[1]);
+  Expect.type<B>(list[1]);
+  Expect.notType<C>(list[1]);
+  Expect.type<X>(list[1]);
+  Expect.type<A>(list[2]);
+  Expect.notType<B>(list[2]);
+  Expect.type<C>(list[2]);
+  Expect.type<X>(list[2]);
+  Expect.notType<A>(list[3]);
+  Expect.notType<B>(list[3]);
+  Expect.notType<C>(list[3]);
+  Expect.type<X>(list[3]);
+}
+
+Future<void> main() async {
+  check();
+  await hotReload();
+
+  helper();
+  check();
+  await hotReload();
+
+  // Revive the class B and make sure all allocated instances take
+  // their place in the inheritance hierarchy.
+  check();
+}
+
+/** DIFF **/
+/*
+ // Adapted from:
+ // https://github.com/dart-lang/sdk/blob/1a486499bf73ee5b007abbe522b94869a1f36d02/runtime/vm/isolate_reload_test.cc#L959
+ 
+-class C {
++class X {
+   String name;
+-  C(this.name);
+-}
+-
+-class X extends C {
+-  X(name) : super(name);
++  X(this.name);
+ }
+ 
+ class A extends X {
+   A(name) : super(name);
+ }
+ 
+-helper() {
+-  list.add(new X('x'));
++class B extends X {
++  B(name) : super(name);
+ }
+ 
++class C extends A {
++  C(name) : super(name);
++}
++
++helper() {}
++
+ var list;
+ 
+ check() {
+   Expect.type<A>(list[0]);
+-  Expect.type<C>(list[0]);
++  Expect.notType<B>(list[0]);
++  Expect.notType<C>(list[0]);
+   Expect.type<X>(list[0]);
+-  Expect.type<A>(list[1]);
+-  Expect.type<C>(list[1]);
++  Expect.notType<A>(list[1]);
++  Expect.type<B>(list[1]);
++  Expect.notType<C>(list[1]);
+   Expect.type<X>(list[1]);
+-  Expect.notType<A>(list[2]);
++  Expect.type<A>(list[2]);
++  Expect.notType<B>(list[2]);
+   Expect.type<C>(list[2]);
+-  Expect.notType<X>(list[2]);
++  Expect.type<X>(list[2]);
+   Expect.notType<A>(list[3]);
+-  Expect.type<C>(list[3]);
++  Expect.notType<B>(list[3]);
++  Expect.notType<C>(list[3]);
+   Expect.type<X>(list[3]);
+ }
+ 
+*/