Add tests for non-primitive equality in switch cases.

Even when a switch case only contains a constant (and not some more
complex pattern), Dart 3.0 changes the semantics and allows constants
of types that don't have primitive equality.

Add some tests for that.

Change-Id: Id3578d017822695451d7e44590fa349a8191a310
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/287663
Commit-Queue: Bob Nystrom <rnystrom@google.com>
Auto-Submit: Bob Nystrom <rnystrom@google.com>
Reviewed-by: Erik Ernst <eernst@google.com>

tests/language/switch/equality_side_effect_test.dart

@@ -0,0 +1,46 @@
+// 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.
+
+// SharedOptions=--enable-experiment=patterns,records
+
+// Switch cases may call user-defined `==` methods, which can have arbitrary
+// side effects. Test that the cases are tried in order.
+
+import "package:expect/expect.dart";
+
+class SideEffect {
+  static final effects = <String>[];
+
+  static String test(int value) {
+    effects.clear();
+
+    switch (SideEffect(value)) {
+      case const SideEffect(1):
+        effects.add('match one');
+      case const SideEffect(2):
+        effects.add('match two');
+      default:
+        effects.add('no match');
+    }
+
+    return effects.join(', ');
+  }
+
+  final int value;
+
+  const SideEffect(this.value);
+
+  String toString() => 'S($value)';
+
+  bool operator ==(Object other) {
+    effects.add('$this == $other');
+    return other is SideEffect && value == other.value;
+  }
+}
+
+main() {
+  Expect.equals('S(1) == S(1), match one', SideEffect.test(1));
+  Expect.equals('S(1) == S(2), S(2) == S(2), match two', SideEffect.test(2));
+  Expect.equals('S(1) == S(3), S(2) == S(3), no match', SideEffect.test(3));
+}

tests/language/switch/non_primitive_equality_test.dart

@@ -0,0 +1,77 @@
+// 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.
+
+// SharedOptions=--enable-experiment=patterns,records
+
+// With Dart 3.0, switch cases are pattersn and constants in cases are no
+// longer required to have primitive equality.
+
+import "package:expect/expect.dart";
+
+class ValueType {
+  static String test(int value) {
+    switch (ValueType(value)) {
+      case const ValueType(1):
+        return 'one';
+      case const ValueType(2):
+        return 'two';
+      default:
+        return 'other';
+    }
+  }
+
+  final int value;
+
+  const ValueType(this.value);
+
+  bool operator ==(Object other) => other is ValueType && value == other.value;
+}
+
+class EquatableToString {
+  static String test(String value) {
+    switch (value) {
+      case const EquatableToString('ape'):
+        return 'primate';
+      case const EquatableToString('bat'):
+        return 'chiroptera';
+      default:
+        return 'other';
+    }
+  }
+
+  final String value;
+
+  const EquatableToString(this.value);
+
+  bool operator ==(Object other) => other is String && value == other;
+}
+
+String testDouble(double value) {
+  switch (value) {
+    case 0.0:
+      return 'nothing';
+    case 1.1:
+      return 'one-ish';
+    case 2.2:
+      return 'two-ish';
+    default:
+      return 'other';
+  }
+}
+
+main() {
+  Expect.equals('one', ValueType.test(1));
+  Expect.equals('two', ValueType.test(2));
+  Expect.equals('other', ValueType.test(3));
+
+  Expect.equals('primate', EquatableToString.test('ape'));
+  Expect.equals('chiroptera', EquatableToString.test('bat'));
+  Expect.equals('other', EquatableToString.test('cat'));
+
+  Expect.equals('nothing', testDouble(0.0));
+  Expect.equals('nothing', testDouble(-0.0));
+  Expect.equals('one-ish', testDouble(1.1));
+  Expect.equals('two-ish', testDouble(2.2));
+  Expect.equals('other', testDouble(3.3));
+}