[JVM IR] ProperVisibilityForCompanionObjectInstanceField

- Uncomment tests
- Add proper visibility to companion field
  + Make exception for interfaces -> they need to respect language versions 1.8
    before they can put private members there.
- Adjust synthetic accessor lowering to look for enclosing classes with access
  via companion object.

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/JvmBackendContext.kt

@@ -69,7 +69,7 @@ class JvmBackendContext(
     val typeMapper = IrTypeMapper(this)
     val methodSignatureMapper = MethodSignatureMapper(this)
 
-    override val declarationFactory: JvmDeclarationFactory = JvmDeclarationFactory(methodSignatureMapper)
+    override val declarationFactory: JvmDeclarationFactory = JvmDeclarationFactory(methodSignatureMapper, state.languageVersionSettings)
     override val sharedVariablesManager = JvmSharedVariablesManager(state.module, builtIns, irBuiltIns)
 
     override val mapping: Mapping = DefaultMapping()

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/descriptors/JvmDeclarationFactory.kt

@@ -13,6 +13,8 @@ import org.jetbrains.kotlin.backend.jvm.codegen.isJvmInterface
 import org.jetbrains.kotlin.backend.jvm.ir.replaceThisByStaticReference
 import org.jetbrains.kotlin.builtins.CompanionObjectMapping.isMappedIntrinsicCompanionObject
 import org.jetbrains.kotlin.codegen.AsmUtil
+import org.jetbrains.kotlin.config.LanguageFeature
+import org.jetbrains.kotlin.config.LanguageVersionSettings
 import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.descriptors.Visibilities
@@ -33,7 +35,8 @@ import org.jetbrains.kotlin.name.Name
 import java.util.*
 
 class JvmDeclarationFactory(
-    private val methodSignatureMapper: MethodSignatureMapper
+    private val methodSignatureMapper: MethodSignatureMapper,
+    private val languageVersionSettings: LanguageVersionSettings
 ) : DeclarationFactory {
     private val singletonFieldDeclarations = HashMap<IrSymbolOwner, IrField>()
     private val interfaceCompanionFieldDeclarations = HashMap<IrSymbolOwner, IrField>()
@@ -137,12 +140,21 @@ class JvmDeclarationFactory(
     override fun getFieldForObjectInstance(singleton: IrClass): IrField =
         singletonFieldDeclarations.getOrPut(singleton) {
             val isNotMappedCompanion = singleton.isCompanion && !isMappedIntrinsicCompanionObject(singleton.descriptor)
+            val useProperVisibilityForCompanion =
+                languageVersionSettings.supportsFeature(LanguageFeature.ProperVisibilityForCompanionObjectInstanceField)
+                        && singleton.isCompanion
+                        && !singleton.parentAsClass.isInterface
             buildField {
                 name = if (isNotMappedCompanion) singleton.name else Name.identifier(JvmAbi.INSTANCE_FIELD)
                 type = singleton.defaultType
                 origin = IrDeclarationOrigin.FIELD_FOR_OBJECT_INSTANCE
                 isFinal = true
                 isStatic = true
+                visibility = when {
+                    !useProperVisibilityForCompanion -> Visibilities.PUBLIC
+                    singleton.visibility == Visibilities.PROTECTED -> JavaVisibilities.PROTECTED_STATIC_VISIBILITY
+                    else -> singleton.visibility
+                }
             }.apply {
                 parent = if (isNotMappedCompanion) singleton.parent else singleton
             }

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

@@ -38,6 +38,7 @@ import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
 import org.jetbrains.kotlin.load.java.JavaVisibilities
 import org.jetbrains.kotlin.load.java.JvmAbi
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.synthetic.isVisibleOutside
 import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 
 internal class SyntheticAccessorLowering(val context: JvmBackendContext) : IrElementTransformerVoidWithContext(), FileLoweringPass {
@@ -48,7 +49,12 @@ internal class SyntheticAccessorLowering(val context: JvmBackendContext) : IrEle
 
     override fun lower(irFile: IrFile) {
         irFile.accept(object : IrInlineReferenceLocator(context) {
-            override fun visitInlineLambda(argument: IrFunctionReference, callee: IrFunction, parameter: IrValueParameter, scope: IrDeclaration) {
+            override fun visitInlineLambda(
+                argument: IrFunctionReference,
+                callee: IrFunction,
+                parameter: IrValueParameter,
+                scope: IrDeclaration
+            ) {
                 inlineLambdaToCallSite[argument.symbol.owner] = LambdaCallSite(scope, parameter.isCrossinline)
             }
         }, null)
@@ -167,7 +173,11 @@ internal class SyntheticAccessorLowering(val context: JvmBackendContext) : IrEle
     private fun IrDeclarationWithVisibility.accessorParent(parent: IrDeclarationParent = this.parent) =
         if (visibility == JavaVisibilities.PROTECTED_STATIC_VISIBILITY) {
             val classes = allScopes.map { it.irElement }.filterIsInstance<IrClass>()
-            classes.lastOrNull { parent is IrClass && it.isSubclassOf(parent) } ?: classes.last()
+            val companions = classes.mapNotNull { it.companionObject() }.filterIsInstance<IrClass>()
+            val objectsInScope =
+                classes.flatMap { it.declarations.filter(IrDeclaration::isAnonymousObject).filterIsInstance<IrClass>() }
+            val candidates = objectsInScope + companions + classes
+            candidates.lastOrNull { parent is IrClass && it.isSubclassOf(parent) } ?: classes.last()
         } else parent
 
     private fun IrConstructor.makeConstructorAccessor(): IrConstructorImpl {
@@ -185,7 +195,9 @@ internal class SyntheticAccessorLowering(val context: JvmBackendContext) : IrEle
             accessor.returnType = source.returnType.remapTypeParameters(source, accessor)
 
             accessor.addValueParameter(
-                "constructor_marker".synthesizedString, context.ir.symbols.defaultConstructorMarker.defaultType, JvmLoweredDeclarationOrigin.SYNTHETIC_ACCESSOR
+                "constructor_marker".synthesizedString,
+                context.ir.symbols.defaultConstructorMarker.defaultType,
+                JvmLoweredDeclarationOrigin.SYNTHETIC_ACCESSOR
             )
 
             accessor.body = IrExpressionBodyImpl(

compiler/testData/codegen/bytecodeText/companion/privateCompanionObjectAccessors_after.kt

@@ -1,6 +1,4 @@
 // !LANGUAGE: +ProperVisibilityForCompanionObjectInstanceField
-// IGNORE_BACKEND: JVM_IR
-// ^ TODO implement ProperVisibilityForCompanionObjectInstanceField feature support in JMV_IR
 
 class Host {
     private companion object {

compiler/testData/codegen/bytecodeText/companion/protectedCompanionObjectAccessors_after.kt

@@ -1,6 +1,4 @@
 // !LANGUAGE: +ProperVisibilityForCompanionObjectInstanceField
-// IGNORE_BACKEND: JVM_IR
-// ^ TODO implement ProperVisibilityForCompanionObjectInstanceField feature support in JMV_IR
 
 // FILE: Base.kt
 package a

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

@@ -6670,6 +6670,7 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
                 runTestWithPackageReplacement("compiler/testData/codegen/box/coroutines/featureIntersection/inlineSuspendFinally.kt", "kotlin.coroutines");
             }
 
+
             @TestMetadata("interfaceMethodWithBody.kt")
             public void testInterfaceMethodWithBody() throws Exception {
                 runTest("compiler/testData/codegen/box/coroutines/featureIntersection/interfaceMethodWithBody.kt");