Report error on unsupported fields of Companion in ObjC subclass [KT-36041] (#4054)

Co-authored-by: Vladimir Ivanov <vladimir.d.ivanov@jetbrains.com>

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/KotlinObjCClassInfoGenerator.kt

@@ -27,7 +27,7 @@ internal class KotlinObjCClassInfoGenerator(override val context: Context) : Con
 
         val instanceMethods = generateInstanceMethodDescs(irClass)
 
-        val companionObject = irClass.declarations.filterIsInstance<IrClass>().atMostOne { it.isCompanion  }
+        val companionObject = irClass.companionObject()
         val classMethods = companionObject?.generateMethodDescs().orEmpty()
 
         val superclassName = irClass.getSuperClassNotAny()!!.let {
@@ -147,4 +147,4 @@ internal fun CodeGenerator.kotlinObjCClassInfo(irClass: IrClass): LLVMValueRef {
     } else {
         context.llvmDeclarations.forClass(irClass).objCDeclarations!!.classInfoGlobal.llvmGlobal
     }
-}
+}

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/InteropLowering.kt

@@ -466,6 +466,15 @@ private class InteropLoweringPart1(val context: Context) : BaseInteropIrTransfor
         }
     }
 
+    private fun IrClass.hasFields() =
+            this.declarations.any {
+                when (it) {
+                    is IrField ->  it.isReal
+                    is IrProperty -> it.isReal && it.backingField != null
+                    else -> false
+                }
+            }
+
     private fun checkKotlinObjCClass(irClass: IrClass) {
         val kind = irClass.descriptor.kind
         if (kind != ClassKind.CLASS && kind != ClassKind.OBJECT) {
@@ -482,6 +491,16 @@ private class InteropLoweringPart1(val context: Context) : BaseInteropIrTransfor
             )
         }
 
+        irClass.companionObject()?.let {
+            if (it.hasFields() ||
+                    it.getSuperClassNotAny()?.hasFields() ?: false) {
+                context.reportCompilationError(
+                        "Fields are not supported for Companion of subclass of ObjC type",
+                        currentFile, irClass
+                )
+            }
+        }
+
         var hasObjCClassSupertype = false
         irClass.descriptor.defaultType.constructor.supertypes.forEach {
             val descriptor = it.constructor.declarationDescriptor as ClassDescriptor