JVM IR: generate kotlin.Metadata.packageName value for JvmPackageName files

Support this for single file facades as well as for multi-file classes,
similar to code in
MultifileClassCodegen.writeKotlinMultifileFacadeAnnotationIfNeeded.
Extend the test on this attribute to also cover multi-file classes.

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/codegen/ClassCodegen.kt

@@ -214,6 +214,10 @@ open class ClassCodegen protected constructor(
                 writeKotlinMetadata(visitor, state, KotlinClassHeader.Kind.CLASS, 0) {
                     AsmUtil.writeAnnotationData(it, serializer, classProto)
                 }
+
+                assert(irClass !in context.classNameOverride) {
+                    "JvmPackageName is not supported for classes: ${irClass.render()}"
+                }
             }
             is MetadataSource.File -> {
                 val packageFqName = irClass.getPackageFragment()!!.fqName
@@ -230,7 +234,9 @@ open class ClassCodegen protected constructor(
                         av.visit(JvmAnnotationNames.METADATA_MULTIFILE_CLASS_NAME_FIELD_NAME, facadeClassName.internalName)
                     }
 
-                    // TODO: JvmPackageName
+                    if (irClass in context.classNameOverride) {
+                        av.visit(JvmAnnotationNames.METADATA_PACKAGE_NAME_FIELD_NAME, irClass.fqNameWhenAvailable!!.parent().asString())
+                    }
                 }
             }
             else -> {

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

@@ -29,6 +29,7 @@ import org.jetbrains.kotlin.fileClasses.JvmFileClassUtil
 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.fqNameWhenAvailable
 import org.jetbrains.kotlin.psi2ir.PsiSourceManager
 import org.jetbrains.kotlin.resolve.jvm.JvmClassName
 import org.jetbrains.kotlin.resolve.source.KotlinSourceElement
@@ -112,7 +113,10 @@ private class FileClassLowering(val context: JvmBackendContext) : FileLoweringPa
                 if (fileClassInfo.withJvmMultifileClass) AsmUtil.asmTypeByFqNameWithoutInnerClasses(fileClassInfo.facadeClassFqName)
                 else null
             context.state.factory.packagePartRegistry.addPart(irFile.fqName, partClassType.internalName, facadeClassType?.internalName)
-            context.classNameOverride[this] = JvmClassName.byInternalName(partClassType.internalName)
+
+            if (fileClassInfo.fileClassFqName != fqNameWhenAvailable) {
+                context.classNameOverride[this] = JvmClassName.byInternalName(partClassType.internalName)
+            }
 
             if (facadeClassType != null) {
                 val jvmClassName = JvmClassName.byInternalName(facadeClassType.internalName)

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

@@ -39,6 +39,7 @@ import org.jetbrains.kotlin.ir.expressions.impl.IrGetFieldImpl
 import org.jetbrains.kotlin.ir.symbols.IrFieldSymbol
 import org.jetbrains.kotlin.ir.symbols.IrFunctionSymbol
 import org.jetbrains.kotlin.ir.util.deepCopyWithSymbols
+import org.jetbrains.kotlin.ir.util.fqNameWhenAvailable
 import org.jetbrains.kotlin.ir.util.transformFlat
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformer
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
@@ -100,14 +101,27 @@ private fun generateMultifileFacades(
     functionDelegates: MutableMap<IrFunctionSymbol, IrFunctionSymbol>
 ): List<IrFile> =
     context.multifileFacadesToAdd.map { (jvmClassName, partClasses) ->
+        val kotlinPackageFqName = partClasses.first().fqNameWhenAvailable!!.parent()
+        if (!partClasses.all { it.fqNameWhenAvailable!!.parent() == kotlinPackageFqName }) {
+            throw UnsupportedOperationException(
+                "Multi-file parts of a facade with JvmPackageName should all lie in the same Kotlin package:\n  " +
+                        partClasses.joinToString("\n  ") { klass ->
+                            "Class ${klass.fqNameWhenAvailable}, JVM name ${context.classNameOverride[klass]}"
+                        }
+            )
+        }
+
         val fileEntry = MultifileFacadeFileEntry(jvmClassName, partClasses.map(IrClass::fileParent))
-        val file = IrFileImpl(fileEntry, EmptyPackageFragmentDescriptor(module, jvmClassName.packageFqName))
+        val file = IrFileImpl(fileEntry, EmptyPackageFragmentDescriptor(module, kotlinPackageFqName))
 
         val facadeClass = buildClass {
             name = jvmClassName.fqNameForTopLevelClassMaybeWithDollars.shortName()
         }.apply {
             parent = file
             createImplicitParameterDeclarationWithWrappedDescriptor()
+            if (jvmClassName.packageFqName != kotlinPackageFqName) {
+                context.classNameOverride[this] = jvmClassName
+            }
         }
         file.declarations.add(facadeClass)