[JVM IR] Make file classes with all private members package-private

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/FileClassLowering.kt

@@ -22,22 +22,20 @@ import org.jetbrains.kotlin.backend.common.phaser.makeIrModulePhase
 import org.jetbrains.kotlin.backend.jvm.JvmBackendContext
 import org.jetbrains.kotlin.codegen.AsmUtil
 import org.jetbrains.kotlin.config.JvmAnalysisFlags
+import org.jetbrains.kotlin.config.LanguageFeature
 import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.descriptors.DescriptorVisibilities
 import org.jetbrains.kotlin.descriptors.Modality
-import org.jetbrains.kotlin.fileClasses.JvmFileClassInfo
 import org.jetbrains.kotlin.fileClasses.JvmFileClassUtil
 import org.jetbrains.kotlin.fileClasses.JvmSimpleFileClassInfo
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.declarations.impl.IrClassImpl
 import org.jetbrains.kotlin.ir.symbols.impl.IrClassSymbolImpl
-import org.jetbrains.kotlin.ir.util.IdSignature
-import org.jetbrains.kotlin.ir.util.NaiveSourceBasedFileEntryImpl
-import org.jetbrains.kotlin.ir.util.fqNameWhenAvailable
-import org.jetbrains.kotlin.ir.util.parentAsClass
+import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.load.java.JavaDescriptorVisibilities
 import org.jetbrains.kotlin.load.kotlin.PackagePartClassUtils
 import org.jetbrains.kotlin.psi2ir.PsiSourceManager
+import org.jetbrains.kotlin.resolve.inline.INLINE_ONLY_ANNOTATION_FQ_NAME
 import org.jetbrains.kotlin.resolve.jvm.JvmClassName
 import java.util.*
 
@@ -61,7 +59,8 @@ private class FileClassLowering(val context: JvmBackendContext) : FileLoweringPa
 
         irFile.declarations.forEach {
             when (it) {
-                is IrScript -> {}
+                is IrScript -> {
+                }
                 is IrClass -> classes.add(it)
                 else -> fileClassMembers.add(it)
             }
@@ -79,19 +78,27 @@ private class FileClassLowering(val context: JvmBackendContext) : FileLoweringPa
 
     private fun createFileClass(irFile: IrFile, fileClassMembers: List<IrDeclaration>): IrClass {
         val fileEntry = irFile.fileEntry
-        val fileClassInfo: JvmFileClassInfo?
-        when (fileEntry) {
+        val fileClassInfo = when (fileEntry) {
             is PsiSourceManager.PsiFileEntry -> {
                 val ktFile = context.psiSourceManager.getKtFile(fileEntry)
                     ?: throw AssertionError("Unexpected file entry: $fileEntry")
-                fileClassInfo = JvmFileClassUtil.getFileClassInfoNoResolve(ktFile)
+                JvmFileClassUtil.getFileClassInfoNoResolve(ktFile)
             }
             is NaiveSourceBasedFileEntryImpl -> {
-                fileClassInfo = JvmSimpleFileClassInfo(PackagePartClassUtils.getPackagePartFqName(irFile.fqName, fileEntry.name), false)
+                JvmSimpleFileClassInfo(PackagePartClassUtils.getPackagePartFqName(irFile.fqName, fileEntry.name), false)
             }
             else -> error("unknown kind of file entry: $fileEntry")
         }
         val isMultifilePart = fileClassInfo.withJvmMultifileClass
+
+        val onlyPrivateDeclarationsAndFeatureIsEnabled =
+            context.state.languageVersionSettings.supportsFeature(LanguageFeature.PackagePrivateFileClassesWithAllPrivateMembers) && fileClassMembers
+                .all {
+                    val isPrivate = it is IrDeclarationWithVisibility && DescriptorVisibilities.isPrivate(it.visibility)
+                    val isInlineOnly = it.hasAnnotation(INLINE_ONLY_ANNOTATION_FQ_NAME)
+                    isPrivate || isInlineOnly
+                }
+
         return IrClassImpl(
             0, fileEntry.maxOffset,
             if (!isMultifilePart || context.state.languageVersionSettings.getFlag(JvmAnalysisFlags.inheritMultifileParts))
@@ -99,7 +106,10 @@ private class FileClassLowering(val context: JvmBackendContext) : FileLoweringPa
             symbol = IrClassSymbolImpl(),
             name = fileClassInfo.fileClassFqName.shortName(),
             kind = ClassKind.CLASS,
-            visibility = if (!isMultifilePart) DescriptorVisibilities.PUBLIC else JavaDescriptorVisibilities.PACKAGE_VISIBILITY,
+            visibility = if (isMultifilePart || onlyPrivateDeclarationsAndFeatureIsEnabled)
+                JavaDescriptorVisibilities.PACKAGE_VISIBILITY
+            else
+                DescriptorVisibilities.PUBLIC,
             modality = Modality.FINAL
         ).apply {
             superTypes = listOf(context.irBuiltIns.anyType)

compiler/testData/codegen/bytecodeListing/fileClassWithPrivateDeclarationsOnly_after.kt

@@ -0,0 +1,14 @@
+// WITH_RUNTIME
+// IGNORE_BACKEND: JVM
+// !LANGUAGE: +PackagePrivateFileClassesWithAllPrivateMembers
+
+private fun f() {
+}
+
+private val a = Unit
+private val b by lazy { Unit }
+
+@Suppress("INVISIBLE_MEMBER", "INVISIBLE_REFERENCE")
+@kotlin.internal.InlineOnly
+public fun g() {
+}

compiler/testData/codegen/bytecodeListing/fileClassWithPrivateDeclarationsOnly_after.txt

@@ -0,0 +1,23 @@
+@kotlin.Metadata
+final class FileClassWithPrivateDeclarationsOnly_afterKt$b$2 {
+    // source: 'fileClassWithPrivateDeclarationsOnly_after.kt'
+    enclosing method FileClassWithPrivateDeclarationsOnly_afterKt.<clinit>()V
+    public final static field INSTANCE: FileClassWithPrivateDeclarationsOnly_afterKt$b$2
+    inner (anonymous) class FileClassWithPrivateDeclarationsOnly_afterKt$b$2
+    static method <clinit>(): void
+    method <init>(): void
+    public synthetic bridge method invoke(): java.lang.Object
+    public final method invoke(): void
+}
+
+@kotlin.Metadata
+final class FileClassWithPrivateDeclarationsOnly_afterKt {
+    // source: 'fileClassWithPrivateDeclarationsOnly_after.kt'
+    private final static @org.jetbrains.annotations.NotNull field a: kotlin.Unit
+    private final static @org.jetbrains.annotations.NotNull field b$delegate: kotlin.Lazy
+    inner (anonymous) class FileClassWithPrivateDeclarationsOnly_afterKt$b$2
+    static method <clinit>(): void
+    private final static method f(): void
+    public final static @kotlin.internal.InlineOnly method g(): void
+    private final static method getB(): kotlin.Unit
+}

compiler/testData/codegen/bytecodeListing/fileClassWithPrivateDeclarationsOnly_before.kt

@@ -0,0 +1,14 @@
+// WITH_RUNTIME
+// IGNORE_BACKEND: JVM
+// !LANGUAGE: -PackagePrivateFileClassesWithAllPrivateMembers
+
+private fun f() {
+}
+
+private val a = Unit
+private val b by lazy { Unit }
+
+@Suppress("INVISIBLE_MEMBER", "INVISIBLE_REFERENCE")
+@kotlin.internal.InlineOnly
+public fun g() {
+}

compiler/testData/codegen/bytecodeListing/fileClassWithPrivateDeclarationsOnly_before.txt

@@ -0,0 +1,23 @@
+@kotlin.Metadata
+final class FileClassWithPrivateDeclarationsOnly_beforeKt$b$2 {
+    // source: 'fileClassWithPrivateDeclarationsOnly_before.kt'
+    enclosing method FileClassWithPrivateDeclarationsOnly_beforeKt.<clinit>()V
+    public final static field INSTANCE: FileClassWithPrivateDeclarationsOnly_beforeKt$b$2
+    inner (anonymous) class FileClassWithPrivateDeclarationsOnly_beforeKt$b$2
+    static method <clinit>(): void
+    method <init>(): void
+    public synthetic bridge method invoke(): java.lang.Object
+    public final method invoke(): void
+}
+
+@kotlin.Metadata
+public final class FileClassWithPrivateDeclarationsOnly_beforeKt {
+    // source: 'fileClassWithPrivateDeclarationsOnly_before.kt'
+    private final static @org.jetbrains.annotations.NotNull field a: kotlin.Unit
+    private final static @org.jetbrains.annotations.NotNull field b$delegate: kotlin.Lazy
+    inner (anonymous) class FileClassWithPrivateDeclarationsOnly_beforeKt$b$2
+    static method <clinit>(): void
+    private final static method f(): void
+    public final static @kotlin.internal.InlineOnly method g(): void
+    private final static method getB(): kotlin.Unit
+}

compiler/tests-gen/org/jetbrains/kotlin/codegen/BytecodeListingTestGenerated.java

@@ -90,6 +90,16 @@ public class BytecodeListingTestGenerated extends AbstractBytecodeListingTest {
         runTest("compiler/testData/codegen/bytecodeListing/extension.kt");
     }
 
+    @TestMetadata("fileClassWithPrivateDeclarationsOnly_after.kt")
+    public void testFileClassWithPrivateDeclarationsOnly_after() throws Exception {
+        runTest("compiler/testData/codegen/bytecodeListing/fileClassWithPrivateDeclarationsOnly_after.kt");
+    }
+
+    @TestMetadata("fileClassWithPrivateDeclarationsOnly_before.kt")
+    public void testFileClassWithPrivateDeclarationsOnly_before() throws Exception {
+        runTest("compiler/testData/codegen/bytecodeListing/fileClassWithPrivateDeclarationsOnly_before.kt");
+    }
+
     @TestMetadata("immutableCollection.kt")
     public void testImmutableCollection() throws Exception {
         runTest("compiler/testData/codegen/bytecodeListing/immutableCollection.kt");

compiler/tests-gen/org/jetbrains/kotlin/codegen/ir/IrBytecodeListingTestGenerated.java

@@ -90,6 +90,16 @@ public class IrBytecodeListingTestGenerated extends AbstractIrBytecodeListingTes
         runTest("compiler/testData/codegen/bytecodeListing/extension.kt");
     }
 
+    @TestMetadata("fileClassWithPrivateDeclarationsOnly_after.kt")
+    public void testFileClassWithPrivateDeclarationsOnly_after() throws Exception {
+        runTest("compiler/testData/codegen/bytecodeListing/fileClassWithPrivateDeclarationsOnly_after.kt");
+    }
+
+    @TestMetadata("fileClassWithPrivateDeclarationsOnly_before.kt")
+    public void testFileClassWithPrivateDeclarationsOnly_before() throws Exception {
+        runTest("compiler/testData/codegen/bytecodeListing/fileClassWithPrivateDeclarationsOnly_before.kt");
+    }
+
     @TestMetadata("immutableCollection.kt")
     public void testImmutableCollection() throws Exception {
         runTest("compiler/testData/codegen/bytecodeListing/immutableCollection.kt");

compiler/util/src/org/jetbrains/kotlin/config/LanguageVersionSettings.kt

@@ -145,6 +145,8 @@ enum class LanguageFeature(
     AllowSealedInheritorsInDifferentFilesOfSamePackage(KOTLIN_1_5),
     SealedInterfaces(KOTLIN_1_5),
     JvmIrEnabledByDefault(KOTLIN_1_5),
+    // Disabled until the breaking change is approved by the committee, see KT-10884.
+    PackagePrivateFileClassesWithAllPrivateMembers(KOTLIN_1_5, defaultState = State.DISABLED),
 
     /*
      * Improvements include the following: