KT-18731 Use reference equality to compare enums

Fix of https://youtrack.jetbrains.com/issue/KT-18731

compiler/backend/src/org/jetbrains/kotlin/codegen/ExpressionCodegen.java

@@ -99,6 +99,7 @@ import static org.jetbrains.kotlin.codegen.inline.InlineCodegenUtilsKt.*;
 import static org.jetbrains.kotlin.resolve.BindingContext.*;
 import static org.jetbrains.kotlin.resolve.BindingContextUtils.getDelegationConstructorCall;
 import static org.jetbrains.kotlin.resolve.BindingContextUtils.isVarCapturedInClosure;
+import static org.jetbrains.kotlin.resolve.DescriptorUtils.isEnumClass;
 import static org.jetbrains.kotlin.resolve.DescriptorUtils.isEnumEntry;
 import static org.jetbrains.kotlin.resolve.DescriptorUtils.isObject;
 import static org.jetbrains.kotlin.resolve.jvm.AsmTypes.*;
@@ -3107,6 +3108,18 @@ public class ExpressionCodegen extends KtVisitor<StackValue, StackValue> impleme
             );
         }
 
+        if ((opToken == KtTokens.EQEQ || opToken == KtTokens.EXCLEQ) &&
+            (isEnumClass(bindingContext.getType(left).getConstructor().getDeclarationDescriptor()) ||
+             isEnumClass(bindingContext.getType(right).getConstructor().getDeclarationDescriptor()))) {
+            // Reference equality can be used for enums.
+            return StackValue.cmp(
+                    opToken == KtTokens.EQEQ ? KtTokens.EQEQEQ : KtTokens.EXCLEQEQEQ,
+                    OBJECT_TYPE,
+                    genLazyUnlessProvided(pregeneratedLeft, left, leftType),
+                    genLazy(right, rightType)
+            );
+        }
+
         return genEqualsForExpressionsPreferIEEE754Arithmetic(left, right, opToken, leftType, rightType, pregeneratedLeft);
     }
 

compiler/testData/codegen/box/enum/kt18731.kt

@@ -0,0 +1,13 @@
+enum class Bar {
+    ONE,
+    TWO
+}
+
+fun isOne(i: Bar) = i == Bar.ONE
+
+fun box(): String {
+    return when (isOne(Bar.ONE) && !isOne(Bar.TWO)) {
+        true -> "OK"
+        else -> "Failure"
+    }
+}

compiler/testData/codegen/bytecodeText/enum/kt18731.kt

@@ -0,0 +1,16 @@
+enum class Bar {
+    ONE,
+    TWO
+}
+
+fun isOne(i: Bar) = i == Bar.ONE
+
+fun box(): String {
+    return when (isOne(Bar.ONE) && !isOne(Bar.TWO)) {
+        true -> "OK"
+        else -> "Failure"
+    }
+}
+
+// 1 IF_ACMPNE
+// 0 INVOKESTATIC kotlin/jvm/internal/Intrinsics.areEqual \(Ljava/lang/Object;Ljava/lang/Object;\)Z

compiler/tests-ir-jvm/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java

@@ -8541,6 +8541,12 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             doTest(fileName);
         }
 
+        @TestMetadata("kt18731.kt")
+        public void testKt18731() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/enum/kt18731.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("kt20651.kt")
         public void testKt20651() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/enum/kt20651.kt");

compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java

@@ -8541,6 +8541,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             doTest(fileName);
         }
 
+        @TestMetadata("kt18731.kt")
+        public void testKt18731() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/enum/kt18731.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("kt20651.kt")
         public void testKt20651() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/enum/kt20651.kt");

compiler/tests/org/jetbrains/kotlin/codegen/BytecodeTextTestGenerated.java

@@ -1270,6 +1270,21 @@ public class BytecodeTextTestGenerated extends AbstractBytecodeTextTest {
         }
     }
 
+    @TestMetadata("compiler/testData/codegen/bytecodeText/enum")
+    @TestDataPath("$PROJECT_ROOT")
+    @RunWith(JUnit3RunnerWithInners.class)
+    public static class Enum extends AbstractBytecodeTextTest {
+        public void testAllFilesPresentInEnum() throws Exception {
+            KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/codegen/bytecodeText/enum"), Pattern.compile("^(.+)\\.kt$"), TargetBackend.ANY, true);
+        }
+
+        @TestMetadata("kt18731.kt")
+        public void testKt18731() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeText/enum/kt18731.kt");
+            doTest(fileName);
+        }
+    }
+
     @TestMetadata("compiler/testData/codegen/bytecodeText/forLoop")
     @TestDataPath("$PROJECT_ROOT")
     @RunWith(JUnit3RunnerWithInners.class)

compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java

@@ -8541,6 +8541,12 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
             doTest(fileName);
         }
 
+        @TestMetadata("kt18731.kt")
+        public void testKt18731() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/enum/kt18731.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("kt20651.kt")
         public void testKt20651() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/enum/kt20651.kt");

js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java

@@ -9225,6 +9225,12 @@ public class JsCodegenBoxTestGenerated extends AbstractJsCodegenBoxTest {
             doTest(fileName);
         }
 
+        @TestMetadata("kt18731.kt")
+        public void testKt18731() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/enum/kt18731.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("kt20651.kt")
         public void testKt20651() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/enum/kt20651.kt");