JVM IR: Convert interface companion fields to static fields.

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

@@ -69,21 +69,27 @@ private class MoveOrCopyCompanionObjectFieldsLowering(val context: CommonBackend
         val companion = irClass.declarations.find {
             it is IrClass && it.isCompanion
         } as IrClass? ?: return
-        if ((irClass.isInterface || irClass.isAnnotationClass) && !companion.allFieldsAreJvmField()) return
+
-        companion.declarations.forEach {
+        // We don't move fields to interfaces unless all fields are annotated with @JvmField.
+        // It is an error to annotate only some of the fields of an interface companion with @JvmField.
+        val newParent = if (irClass.isJvmInterface && !companion.allFieldsAreJvmField()) companion else irClass
+
+        val newDeclarations = companion.declarations.mapNotNull {
             when (it) {
-                is IrProperty -> {
+                is IrProperty ->
-                    val newField = movePropertyFieldToStaticParent(it, companion, irClass, fieldReplacementMap)
+                    movePropertyFieldToStaticParent(it, companion, newParent, fieldReplacementMap)
-                    if (newField != null) irClass.declarations.add(newField)
+                is IrAnonymousInitializer ->
-                }
+                    moveAnonymousInitializerToStaticParent(it, companion, newParent)
-                is IrAnonymousInitializer -> {
+                else ->
-                    val newInitializer = moveAnonymousInitializerToStaticParent(it, companion, irClass)
+                    null
-                    irClass.declarations.add(newInitializer)
-                }
-                else -> Unit
             }
         }
-        companion.declarations.removeAll { it is IrAnonymousInitializer }
+
+        // Move declarations to parent if required
+        if (newParent !== companion) {
+            companion.declarations.removeAll { it is IrAnonymousInitializer }
+            newParent.declarations += newDeclarations
+        }
     }
 
     private fun copyConsts(irClass: IrClass) {

compiler/testData/codegen/box/objects/interfaceCompanion.kt

@@ -1,3 +1,7 @@
+// IGNORE_BACKEND: JVM_IR
+// Inside of the companion we have to access the instance through the local Companion field,
+// not by indirection through the Companion field of the enclosing class.
+// Class initialization might not have finished yet.
 var result = ""
 
 interface A {

compiler/testData/codegen/bytecodeText/companion/kt14258_5.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 // Checks that accessor are not used because property can be accessed directly.
 
 interface I {

compiler/testData/codegen/bytecodeText/constProperty/nonConstValHasNoDefaultValue_after.kt

@@ -1,5 +1,4 @@
 // !LANGUAGE: +NoConstantValueAttributeForNonConstVals +JvmFieldInInterface
-// IGNORE_BACKEND: JVM_IR
 
 class C {
     val testClassVal = 100

compiler/testData/writeFlags/property/classObject/trait/delegatedProtectedVar.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 import kotlin.reflect.KProperty
 
 class TestDelegate() {

compiler/testData/writeFlags/property/classObject/trait/delegatedPublicVal.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 import kotlin.reflect.KProperty
 
 class TestDelegate() {

compiler/testData/writeFlags/property/classObject/trait/internalConstVal.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 interface Test {
   companion object {
     internal const val prop: Int = 0;

compiler/testData/writeFlags/property/classObject/trait/privateVal.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 interface Test {
   companion object {
     private val prop = 0;

compiler/testData/writeFlags/property/classObject/trait/privateVar.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 interface Test {
   companion object {
     private var prop = 0;

compiler/testData/writeFlags/property/classObject/trait/publicConstVal.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 interface Test {
   companion object {
     public const val prop: Int = 0;