KT-4107 Data objects

compiler/testData/codegen/box/dataObjects/equals.kt

@@ -0,0 +1,15 @@
+// LANGUAGE: +DataObjects
+// WITH_STDLIB
+
+package com.example
+
+import kotlin.test.*
+
+data object DataObject
+
+fun box(): String {
+    assertEquals(DataObject, DataObject)
+    assertFalse(DataObject == null)
+
+    return  "OK"
+}

compiler/testData/codegen/box/dataObjects/hashCode.kt

@@ -0,0 +1,19 @@
+// LANGUAGE: +DataObjects
+// WITH_STDLIB
+
+package com.example
+
+import kotlin.test.*
+
+data object DataObject {
+    data object Inner
+}
+
+fun box(): String {
+    assertEquals(DataObject.hashCode(), DataObject.hashCode())
+    assertNotEquals(DataObject.hashCode(), DataObject.Inner.hashCode())
+    assertNotEquals(0, DataObject.hashCode())
+    assertNotEquals(0, DataObject.Inner.hashCode())
+
+    return "OK"
+}

compiler/testData/codegen/box/dataObjects/multipleInstances.kt

@@ -0,0 +1,18 @@
+// LANGUAGE: +DataObjects
+// WITH_STDLIB
+// TARGET_BACKEND: JVM_IR
+
+import kotlin.test.*
+
+data object DataObject
+
+val doppelganger = DataObject::class.java.declaredConstructors[0].apply { isAccessible = true }.newInstance()
+
+fun box(): String {
+    assertFalse(DataObject === doppelganger)
+    assertEquals(DataObject, doppelganger)
+    assertEquals(DataObject.hashCode(), DataObject::class.java.cast(doppelganger).hashCode())
+
+    return  "OK"
+}
+

compiler/testData/codegen/box/dataObjects/serialization.kt

@@ -0,0 +1,19 @@
+// LANGUAGE: +DataObjects
+// WITH_STDLIB
+// TARGET_BACKEND: JVM_IR
+// FULL_JDK
+// CHECK_BYTECODE_LISTING
+
+import java.io.*
+
+data object NonSerializableDataObject
+
+data object SerializableDataObject: Serializable
+
+fun box(): String {
+    ByteArrayOutputStream().use { baos ->
+        ObjectOutputStream(baos).use { oos -> oos.writeObject(SerializableDataObject) }
+        ByteArrayInputStream(baos.toByteArray()).use { bais -> assert(java.io.ObjectInputStream(bais).readObject() === SerializableDataObject) }
+    }
+    return "OK"
+}

compiler/testData/codegen/box/dataObjects/serialization.txt

@@ -0,0 +1,28 @@
+@kotlin.Metadata
+public final class NonSerializableDataObject {
+    // source: 'serialization.kt'
+    public final static @org.jetbrains.annotations.NotNull field INSTANCE: NonSerializableDataObject
+    static method <clinit>(): void
+    private method <init>(): void
+    public method equals(@org.jetbrains.annotations.Nullable p0: java.lang.Object): boolean
+    public method hashCode(): int
+    public @org.jetbrains.annotations.NotNull method toString(): java.lang.String
+}
+
+@kotlin.Metadata
+public final class SerializableDataObject {
+    // source: 'serialization.kt'
+    public final static @org.jetbrains.annotations.NotNull field INSTANCE: SerializableDataObject
+    static method <clinit>(): void
+    private method <init>(): void
+    public method equals(@org.jetbrains.annotations.Nullable p0: java.lang.Object): boolean
+    public method hashCode(): int
+    private final method readResolve(): java.lang.Object
+    public @org.jetbrains.annotations.NotNull method toString(): java.lang.String
+}
+
+@kotlin.Metadata
+public final class SerializationKt {
+    // source: 'serialization.kt'
+    public final static @org.jetbrains.annotations.NotNull method box(): java.lang.String
+}

compiler/testData/codegen/box/dataObjects/toString.kt

@@ -0,0 +1,52 @@
+// LANGUAGE: +DataObjects
+// WITH_STDLIB
+
+package com.example
+
+import kotlin.test.*
+
+data object DataObject {
+    data object Nested
+}
+
+class Foo {
+    data object Inner
+}
+
+data object Declared {
+    override fun toString() = "Overriden"
+}
+
+open class WithFinalToString {
+    final override fun toString() = "FinalToString"
+}
+
+data object InheritedFromClassWithFinalToString: WithFinalToString()
+
+open class WithOpenToString {
+    override fun toString() = "OpenToString"
+}
+
+data object InheritedFromClassWithOpenToString: WithOpenToString()
+
+abstract class WithAbstractToString {
+    abstract override fun toString(): String
+}
+
+data object InheritedFromClassWithAbstractToString : WithAbstractToString()
+
+class C {
+    companion object CC
+}
+
+fun box(): String {
+    assertEquals("DataObject", DataObject.toString())
+    assertEquals("Nested", DataObject.Nested.toString())
+    assertEquals("Inner", Foo.Inner.toString())
+    assertEquals("Overriden", Declared.toString())
+    assertEquals("FinalToString", InheritedFromClassWithFinalToString.toString())
+    assertEquals("InheritedFromClassWithOpenToString", InheritedFromClassWithOpenToString.toString())
+    assertEquals("InheritedFromClassWithAbstractToString", InheritedFromClassWithAbstractToString.toString())
+
+    return "OK"
+}