Move test_types_in_equals tests (#4550)

test/rules/all.dart

@@ -124,6 +124,7 @@ import 'sort_constructors_first_test.dart' as sort_constructors_first;
 import 'sort_pub_dependencies_test.dart' as sort_pub_dependencies;
 import 'sort_unnamed_constructors_first_test.dart'
     as sort_unnamed_constructors_first;
+import 'test_types_in_equals_test.dart' as test_types_in_equals;
 import 'throw_in_finally_test.dart' as throw_in_finally;
 import 'tighten_type_of_initializing_formals_test.dart'
     as tighten_type_of_initializing_formals;
@@ -275,6 +276,7 @@ void main() {
   sort_constructors_first.main();
   sort_pub_dependencies.main();
   sort_unnamed_constructors_first.main();
+  test_types_in_equals.main();
   throw_in_finally.main();
   tighten_type_of_initializing_formals.main();
   type_init_formals.main();

test/rules/test_types_in_equals_test.dart

@@ -0,0 +1,51 @@
+// Copyright (c) 2023, 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:test_reflective_loader/test_reflective_loader.dart';
+
+import '../rule_test_support.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(TestTypesInEqualsTest);
+  });
+}
+
+@reflectiveTest
+class TestTypesInEqualsTest extends LintRuleTest {
+  @override
+  String get lintRule => 'test_types_in_equals';
+
+  test_usesIs() async {
+    await assertNoDiagnostics(r'''
+class C {
+  int? x;
+
+  @override
+  bool operator ==(Object other) {
+    if (identical(this, other)) {
+      return true;
+    }
+    return other is C && this.x == other.x;
+  }
+}
+''');
+  }
+
+  test_doesNotUseIs() async {
+    await assertDiagnostics(r'''
+class C {
+  int? x;
+
+  @override
+  bool operator ==(Object other) {
+    C otherC = other as C;
+    return otherC.x == x;
+  }
+}
+''', [
+      lint(83, 10),
+    ]);
+  }
+}